Insecticide decision protocols: a case study of untrained Filipino rice farmers

Crop Protection 21 (2002) 803–816

Insecticide decision protocols: a case study of untrained Filipino rice farmers J.P. Bandonga, B.L. Canapia, C.G. dela Cruza, J.A. Litsingerb,* a

International Rice Research Institute, DAPO Box 7777, Metro Manila, Philippines b 1365 Jacobs Place, Dixon, CA 95620 USA Received 24 July 2001; accepted 20 February 2002

Abstract Surveys in four irrigated rice sites in the Philippines over a span of eight years (1984–91) focused on farmers’ insecticide decision making protocol before formalized farmer field school training programmes. Despite past extension campaigns to the contrary, farmers based their decisions more on crop monitoring than prophylaxis. Farmers were deficient in pest identification skills using terms such as worms, moths, and hoppers while some farmers targeted beneficials. Farmers mostly based decisions on planthoppers, leafhoppers, and moths by seeing the insect pest, on whorl maggot, defoliators, and leaffolders by noting damage, and on rice bug and seedbed pests by prophylaxis. Decision protocols were largely site specific based on different pest complexes and outbreak histories as well as being highly farmer specific. A large proportion of prophylactic applications during the early crop stages was timed with fertilizer application. Farmers’ frequency of field visitation was as recommended for pests, but reasons to visit the field at the time of a spray decision were predominantly water management. A generalized pattern emerged with monitoring starting on the way to the farmer’s field. Some decisions were prompted upon seeing infestation in an earlier planted field or a neighbour spraying. A number of farmers sought lower lying more flooded parcels or downwind sides of parcels to visit first as these microhabitats favour greater pest densities. Most decisions were made while walking along the field border observing patches of damage or flushed moths with the unit of measure being the parcel. The field was entered only as a last resort. Farmers’ action thresholds were lower than those of researchers and sampling was less rigorous. A minority of farmers, however, expressed insect pest abundance in quantitative terms using sampling units of several rice hills, distance of rice rows, and per panicle. Some of the more innovative farmers’ pest assessment methods were tested later by researchers. r 2002 Elsevier Science Ltd. All rights reserved. Keywords: Rice; Insecticide use; Farmer survey; Decision making; Farmers’ perceptions

1. Introduction Agro-inputs including insecticides were first adopted on a mass scale by Filipino rice farmers in 1973 via government sponsored credit, the Masagana 99 rice production program (NFAC, 1974; Kenmore et al., 1987; IRRI, 1988). Insecticides were part of the loan package. Farmers were required to attend extension meetings, which emphasized prophylactic insecticide application. The heart of the Masagana 99 program was a ‘cook book’ approach, which simplified the extension message where farmers were instructed to follow 16 steps to successful rice culture. *Corresponding author. Tel.: +1-707-678-9068; fax: +1-707-6789069. E-mail address: [email protected] (J.A. Litsinger).

The 16 steps were tied to crop growth stages and four of these steps involved prophylactic insecticide application beginning in the seedbed. As the extension agent also co-signed for credit approval, most of the extension meetings centred around credit issues rather than increasing farmers’ skills at pest identification. The crop-stage approach to input application was further strengthened by chemical company representatives who participated in promotional campaigns carried out at the village level. Placards advertising pesticide brands were placed in farmers’ fields. Caps and shirts replete with pesticide brand logos were given to farmers along with free insecticide samples. Credit was also extended by rice buyers and agroinput dealers who supplied pesticides to farmers before each crop season. Cash-strapped farmers repaid from their harvest at high interest rates. By the time crop

0261-2194/02/$ - see front matter r 2002 Elsevier Science Ltd. All rights reserved. PII: S 0 2 6 1 - 2 1 9 4 ( 0 2 ) 0 0 0 4 3 - 1

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monitoring and use of action thresholds became part of pest management messages beginning in 1977 (PCARR, 1977), the government’s low interest credit program had essentially ended as a result of a high default rate, as most farmers viewed credit as a gift from the government. Extension services to farm communities had virtually collapsed by the 1980s and visits to rural areas became infrequent due to lack of budget to cover transportation costs from the town office. Extension efforts in pest management have been revived in a new thrust involving farmer field schools (Matteson et al., 1994) that were at the pilot stage of development at the time of this study but were not active in any of the study site villages. It is informative to learn of farmer-developed pest monitoring methods before the National Integrated Pest Management (IPM) Program began. With current interest in farmer training, it would be useful to build upon farmers’ existing systems rather than to totally replace them and to relate introduced concepts to those already held. Studying farmers’ practices that are used in making insecticide application decisions may result in new techniques of use to researchers.

2. Methods 2.1. General Research staff from the Department of Agriculture and the International Rice Research Institute (IRRI) were assigned in each of four irrigated rice areas in the Philippines. Enumerators were members of the field staff that had been hired locally to assist in the conduct of onfarm research trials under the supervision of a college educated entomologist stationed at the site. Duties of the field staff included sampling of rice pests in research trials thus they were familiar with the insect pests as well as the local farmers and language. They knew the local terms for the pests and could correlate farmers’ descriptions of pests to species. Central and Southern Luzon have distinct wet and dry seasons, and without irrigation no dry season crop could be grown. In Mindanao, however, the rainy season is longer thus the rice crops are referred to as first and second crops. 2.2. Site descriptions All survey sites were in irrigated, double-rice crop areas with 1–2 ha farms. Zaragoza and Guimba are sites in Nueva Ecija province in Central Luzon while Calauan lies in Southern Luzon in Laguna province. A fourth site located in Koronadal, South Cotabato province in Mindanao was selected as it had experienced outbreaks and crop failures from brown planthopper and green leafhopper in the early 1980s. Zaragoza

comprised the villages of Marawa, Malabon Kaingin, Imbunia, Rajal Norte, and Batitang in portions of Zaragoza, Jaen, and Santa Rosa towns. Zaragoza farmers’ fields lie at the lower end of the Upper Pampanga River system so they plant late in the wet season. Crops are nearing maturity during the time of the strongest typhoons (between October 15 and November 15) and traditionally suffer severe damage every three or four years. Crops can suffer directly from flooding or lodging or indirectly by diseases that spread as a result of wind whipped foliage or to harvested grain that cannot be dried. Further description of farmers and the area is given by Goodell et al. (1982). A survey in the area in 1982 revealed farmers had an average of four years of schooling and had been farming an average of 26 years. Despite the Masagana 99 extension program most (63%) of farmers obtained information on pest control from their neighbours or relatives and only 13% had received any training. The limited training was usually performed by the local government technician and lasted one day. None of the farmers in the survey had attended more than three training sessions and none included hands-on training. The Guimba site was located in the village of Bantug next to the Cropping Systems Program research site in nearby San Roque and Macatcatwit. Irrigation comes from deep well pumps, one per village, each with a command area of 60–100 ha. Farmers plant their wet season crop earlier and normally avoid the most severe typhoons, but tungro virus was endemic in the area. Losses can be extremely high but localized from tungro. The electric pumps are expensive to maintain and break down often leading to drought stress. Further site description is given in IRRI (1985a). The Calauan site was located 10 km east of the IRRI research centre in the villages of Pulong and Dayap. The rice area is irrigated by diverting water via feeding Laguna de Bay lake from the nearby volcanic Mt. Makiling watershed. The villages are located along the edge of lake but away from the perennial flood zone. Calauan farmers experienced large-scale tungro outbreaks in the early 1970s. In Koronadal the villages of Namnama, Magsaysay, Barrio 1, Avancenia, and Morales were selected in the Marbel River Irrigation System. Koronadal is out of the typhoon belt but had been the site of large outbreaks of tungro, grassy stunt, and brown planthopper ‘hopperburn’ in early to mid 1980s. A further site description is given in IRRI (1985b, 1988). 2.3. Farmer surveys Farmers included in the surveys were randomly selected from lists provided by the village leaders from those belonging to the local irrigators’ association. Each season farmers were selected from the list who agreed to

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participate by enumerating their crop production practices in a record book during the growing season. The number of farmers varied each season depending on time available from the enumerators and will of the farmers. Thus makeup of farmers in the sample changed each year. Enumerators visited farmers at two-week intervals to review the entries of field operations. A summary of the numbers of farmers surveyed by season and site is in Table 1. The study spanned a period when farmers were changing from transplanting to direct seeding due mainly to increasing labour costs. Insecticide was also taken from the seedbed of transplanted crops. Farmers in Calauan and Koronadal practiced ‘dapog’ seedbeds which were transplanted at 10–14 days old rather than the normal wet seedbed age of 3–4 weeks. 2.4. Insecticide decision making When a farmer revealed that he had applied an insecticide he was questioned in detail on the reasons leading up to making the decision including the target pest and his assessment of its abundance, how he measured it, and the reason for going to the field when the decision was made. He was asked to recall his observations from the time he left his home until the decision was made. Thus his observations on the way to the field were noted as well as which parcel he chose to observe first. Rice fields are divided by bunds into parcels from high-lying to low-lying positions. Dikes line irrigation canals can form field borders. The shape of each parcel is dictated by the slope and topography of the land leading from the source of irrigation. Fields are typically long and narrow and rectangular in shape with the short side adjoining an irrigation dike. It is important to understand that the data are presented as percentages of responses rather than percentages of farmers, as farmers often had mixed responses depending on the situation. Statistical comparisons between decision modes and sites were first made by ANOVA performed by SAS. Percentages were transformed by arc sine and whenever significant differences were found (Po0:05) the Least Significant Difference (LSD) test was used to separate means.

3. Results 3.1. Visitation frequency and reasons for visiting the field when a spray decision made Although survey results did not record farmers’ field visitation frequency it was commonly observed that farmers visited their fields at least once a week on average between planting and harvest. Reasons for visiting fields at the time of a spray decision were

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grouped into categories and the results varied by location. Zaragoza and Guimba farmers were more concerned about checking field water levels, whereas Koronadal farmers were primarily concerned about pests. In Zaragoza water management activities (38% of responses) were the primary reason to initiate field visits when spray decisions were made. Water management activities centred around ensuring adequate ponding for the crop which included monitoring water levels in the fields, inspecting for leaks in the bunds, and checking on water delivery from river diversion canals. Pest control activities were the second most common category (25%) with weeding being the primary reason. The pest control category also included when a farmer was spraying in one parcel and observed insect pests in another. The third and fourth most common reasons given were fertilisation (13%) and maintaining and cleaning bunds and dikes (12%). The least mentioned reasons were to monitor insect pests (7%) and check crop growth (5%). In Guimba, with less assured water delivery from locally managed pumps, water management ranked as the highest reason (52%). The operational time of the pump was very limited because of cost, thus farmers had to be vigilant as neighbours often diverted water illegally. This was followed by pest control activities (26%) (mainly weed control) followed by fertilisation (5%), checking crop growth (3%), and cleaning bunds and dikes (2%). In Koronadal, having a history of recent pest outbreaks, farmers most frequently visited the field for pest monitoring (52% of responses). Pest monitoring included farmers checking on the effect of insecticide after application. Pest control was the next most common reason mentioned (22%), which consisted of weeding (18% of responses) followed by insecticide application and placing rat bait (both 2%). Water management and fertilisation followed (both 8%). Water management included checking the water level (4%) as well as irrigating (2%) and draining (2%) fields. Least important reasons included checking on the crop growth stage (6%), replanting (2%), and removing coconut fronds (2%). 3.2. Monitoring pattern A consistent pattern emerged among the sites with most insecticide decisions (66–87% of responses) based on monitoring without entering the field. The most detailed responses came from Zaragoza and were classified by crop growth stage or by target pest—85% of decisions in seedbed, 91% in vegetative stage, 92% for leaffolders, 81% for leafhoppers and planthoppers, 91% for stemborers, and 100% for rice bug—made from the field edge. Some farmers showed innovative crop monitoring techniques. In the seedbed 10% of decisions were made after tapping the seedlings to

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Table 1 Basis of farmers’ insecticide decisions in the seedbed and main crop in four irrigated rice locations, Philippines 1984–91 Site

Crop year

Season

Farmers (no.)

Farmer users (%)

Applications (no.)

Zaragoza ‘84 ‘85

Basis of farmers’ applications (%)a Presence of insect damage

Presence of insects

Prophylaxis

Main crop 37 39 53 25 43 39 39 A a

41 27 1 29 31 53 30 A ab

19 33 44 46 26 7 29 A a

‘87

Wet Dry Wet Dry Wet Wet

62 35 42 34 42 30 Average

98 100 98 91 88 92

161 102 113 56 78 55

‘84 ‘85

Wet Dry

62 35 Average

77 94

72 94

Seedbed 13 14 14

44 57 51

43 29 36

‘85 ‘86

‘91

Wet Dry Wet Dry Wet Dry Dry Wet Dry

30 29 30 40 40 38 25 38 30 Average

80 93 77 85 70 74 60 58 38

29 54 32 61 36 39 18 29 23

Main crop 16 6 21 8 3 46 34 9 35 20 B b

39 73 68 60 37 18 27 59 28 45 A a

45 21 11 32 60 36 39 32 37 35 AB a

‘85 ‘86 ‘87 ‘88 ‘89

Wet Dry Dry Wet Dry

30 29 40 40 38 Average

67 79 53 70 53

20 30 23 31 20

Seedbed 10 0 5 0 0 3Bb

38 37 47 37 53 42 A a

52 63 48 63 47 55 A a

‘84

‘87 ‘91

1st 2nd 1st 2nd 1st 2nd 2nd 1st

36 34 44 35 46 30 29 17 Average

92 100 98 97 96 90 76 94

106 102 134 98 155 81 40 46

Main crop 48 48 31 32 58 26 64 36 43 A a

20 18 10 7 16 18 25 12 16 B b

32 34 59 61 26 56 11 52 41 A a

‘84

2nd

34

74

28

Seedbed 36

28

36

‘87

Dry

29

99

57

Main crop 55

17

28

‘86

Guimba

‘87 ‘88 ‘89 ‘90

Koronadal

‘85 ‘86

Calauan a

Means within a row followed by the same upper case letter are not significantly different nor are means among columns followed by the same lower case letter significantly different at the 5% level by LSD.

dislodge insects onto the water surface, a method used by researchers; while 5% of decisions were based on the pest situation seen in an earlier planted neighbour’s seedbed. The lowest lying parcel was selected in 33% of

occasions during the vegetative stage and 13% for leaffolders; while, high-lying parcels were sought in 2% of occasions for leaffolders and 15% for stemborers. Some responses (2%) were based on scouting on the

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Zaragoza farmers, however, apparently are more observant and noted the larvae as the applications were equally divided between the three decision modes. Whorl maggot Hydrellia philippina Ferino is recognized by leaf injury thus most applications in both sites were based on seeing damage. About a third of applications in both sites were based on prophylaxis for this pest, most likely as a result of prior experience. Two lepidopterous defoliators—the semi-looper Naranga aenescens Moore and green hairy caterpillar Rivula artimeta (Swinhoe)—also attack in the vegetative stage, and the small green larvae can be seen by a trained eye. Their damage can be discerned from that of whorl maggot. In both sites most applications were based on damage. In Zaragoza three times more applications were based on seeing the insect than in Koronadal. Prophylactic decisions were more in Koronadal than in Zaragoza. Caseworm Nymphula depunctalis (Guene! e) larvae prefer vegetative stage plants. This semi-aquatic pest is more common in Zaragoza than Koronadal. Most decisions in Zaragoza were based on damage rather than the insect or by prophylaxis. Leaffolders, predominantly Cnaphalocrocis medinalis (Guene! e), Marasmia exigua (Butler), and Marasmia patnalis (Bradley), have a distinctive damage symptom of a folded leaf within which the larva feeds. The damage symptom of the folded leaf was cited in most cases when spray decisions were made for it in both sites. Many farmers referred to seeing ‘worms’ or their damage during the vegetative and reproductive stages. The term ‘worms’ is the direct translation of the farmers’ response. The enumerator could not decide what pest this term

downwind side of a parcel during the vegetative stage, probably for caseworm. Farmers tapped hills either from the bund or after entering the field. One response for defoliators was based on submerging several hills underwater to cause semi-looper or hairy caterpillar larvae to float upwards for easier viewing. The green larvae are the colour of rice plants and difficult to discern directly on the plants. 21% of responses for leafhoppers and planthoppers were based on tapping the plants while 15% were based on observing insects on the plants directly. The survey revealed a small number of farmers in Zaragoza on occasions enter fields and follow one of three generalized monitoring patterns. Most just cross to the other side of the parcel (6% of respondents) but some make a conscious zigzag pattern (2%) while others walk in a circle (1%). 3.3. Target pests The identification of target pests for each insecticide decision was carried out in Zaragoza and Koronadal (Table 2). The first grouping includes armyworm Mythimna separata (Walker) and cutworms Spodoptera litura (F.), S. mauritia (Boisduval), and S. exigua (Hubner). Both armyworm and cutworms can attack all stages of the crop causing defoliation. The larvae are large and often feed in groups thus farmers are likely to see the damage. As feeding is more prominent during the night the larvae would require searching to see once the damage was noted. This was the case in Koronadal with most applications based upon seeing defoliation while few decisions were as a result of seeing the larvae.

Table 2 Summary of insect pest targets by insecticide decision mode in Zaragoza and Koronadal Applications by pest (%) Zaragoza responses

Koronadal responses

Insect group

(%)

Damage

Insect

Prophylaxis

(%)

Damage

Insect

Prophylaxis

Armyworms/cutworms Whorl maggot Defoliators Caseworm Leaffolders Worms Moths Leafhoppers Planthopper Hoppers Greenhorned caterpillar Stemborers Rice bug Lady beetlesa None specified

2 2 19 7 20 19 5 2 6 7 0 5 3 1 2

33 60 49 62 65 50 34 17 0 45 0 64 16 0 7

33 7 44 28 25 50 54 77 87 36 0 14 4 67 3

33 33 7 10 10 0 12 6 13 19 0 22 80 33 90

2 8 22 0 9 14 1 5 5 6 1 11 14 0 2

85 61 53 0 75 77 27 31 15 12 30 40 3 0 3

4 10 15 0 9 10 58 48 62 43 70 17 3 0 20

11 29 32 0 16 13 15 21 23 44 0 43 94 0 77

a

Beneficial species.

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referred to. These ‘worms’ were probably the larval stages of armyworms, cutworms, defoliators, caseworm, or leaffolders. In Zaragoza equal numbers of decisions were based on ‘worm’ damage and seeing the insect. In Koronadal most applications were based on seeing the damage. Farmers also recognize ‘moths’ as a pest but as with ‘worms’ the enumerator could not distinguish among the various species of lepidopterous pests. Moths of various pest species are readily noticed while walking through the field or along grassy dikes and can flush up in great numbers. During the vegetative and reproductive stages these moths can be green semi-looper, green hairy caterpillar, leaffolders, caseworm, and stemborers or mixtures thereof. Farmers do understand insect life cycles to be able to connect moths to subsequent larvae. Green leafhopper Nephotettix virescens (Distant) does not cause direct damage but vectors tungro virus disease and outbreaks had recently occurred in both locations, particularly Koronadal. The insect is distinctive and is located in the upper part of the plant thus is recognized by most farmers. Most applications were in response to seeing the insect rather than seeing the tungro damage or prophylaxis. Brown planthopper Nilaparvata lugens (Sta( l) and whitebacked planthopper Sogatella furcifera (Horvarth) are also common pests in lowland rice and no farmer ever interviewed has been able to distinguish between the species. Planthopper outbreaks had also occurred in the recent past in both areas causing hopperburn and, in the case of brown planthopper, grassy stunt disease. Most applications directed against planthoppers were made upon seeing the insects in the field. Some farmers cannot distinguish leafhoppers and planthoppers thus lump them under the term ‘hoppers’. In Zaragoza most responses to unspecified ‘hoppers’ were based on damage, whereas in Koronadal were equally based on both prophylaxis or the insect. The greenhorned caterpillar Melanitis leda ismene (Cramer) is a large butterfly larva with distinct horn-like structures and is common in Koronadal but not Zaragoza. Koronadal farmers were prone to spray for it is based on sighting the larvae. The most common stemborers are yellow Scirpophaga incertulas (Walker) in both sites with white Scirpophaga innotata (Walker) occurs in Koronadal. Stemborer larvae produce distinctive deadheart (wilted tiller) and whitehead (dried panicle) damage symptoms. Most applications in Zaragoza were based on damage. In Koronadal, however, near equal responses occurred between the prophylaxis and damage. At the ripening stage the large and odorous rice seed bug Leptocorisa oratorius (F.) is well known by farmers, but most decisions in both sites were based on prophylaxis. Farmers place high priority in protecting the grains but may confuse brown spots on the spikelets caused by various fungi with rice bug injury. Fungal

damage is more common than rice bug damage. Modern rice also results in high percentages of unfilled grains which farmers may mistake for rice bug damage. Both brown spots and unfilled grains are blamed on rice bug (Litsinger et al., 1998). Various species of lady beetles feed on the pollen in the panicles and are seen in Zaragoza as pests when in fact their damage is nil as pollination has occurred before the spikelets open. Lady beetles are beneficial predators. Farmers spray when the adult or larva is seen. Of those farmers that did not specify a type of insect they were more prone to apply by prophylaxis. In Calauan the modes were not disaggregated by target pests but the overall target pests were stemborers (39% of applications), leaf/planthoppers (30%), leaffolder (15%), whorl maggot (9%), and defoliators (7%).

3.4. Decision mode Farmers applied insecticides as sprays 95% of the time using knapsack sprayers with the balance as granules. Farmers’ decisions to apply insecticide were divided into three modes. The first decision mode was based on prophylaxis either by crop age, by the calendar (e.g., every two weeks), or tied to application of fertiliser where a decision is made without monitoring. The second decision mode is recognition of insects, usually larger or more mobile species. The third decision mode is based on the presence of insect damage usually defined as defoliation or discolouration (yellowing, white, or brown). As an average over years and seasons in Zaragoza there was no significant difference in the decision frequency based on either insect damage, the presence of insects, or prophylaxis (Table 1). In the seedbed, most of the decisions were based on the presence of insects followed by prophylaxis and damage. Of the prophylactic responses most (67%) were based on crop growth stage, applying just before pulling the seedlings (so there would be a carryover residual effect of the insecticide to the main crop) (25%), or timed with fertilisation (8%). Other reasons for prophylactic applications were upon seeing a neighbour spray (3%) and one farmer sprayed based on weakened seedlings (to insect pest attack) as a result of flooding after heavy rains. Prophylactic applications were also summarized by insect pest. For leaffolders 80% of prophylactic responses were based on the age of seedlings, while 10% each were based upon fertilisation or seeing a neighbour spray. For planthoppers or leafhoppers most (91%) were based on crop age while 9% were in response to seeing a neighbour spray. For stemborers, (73%) were based on the crop growth stage and (27%) timed with fertilisation. For rice bug 100% were based on crop stage.

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In the follow-up survey of Zaragoza farmers’ opinions regarding the timing of insecticide in relation to fertilizer use, all farmers in the sample applied inorganic fertilizer to their rice crop during both seasons. Most of the farmers interviewed (66%) stated that for some insecticide applications their timing was influenced by the timing of fertilizer, particularly during the vegetative stage but even in the seedbed. The most dominant belief elicited was that the applied fertilizer made the rice plant soft and thus more susceptible to insect pest damage, therefore insecticide was used prophylactically to protect the plant during this vulnerable period. Aside from greater damage, farmers also believed that pest numbers increased as a result of fertilizer usage. Of the farmers who held these perceptions, all believed that susceptibility occurred among all insect pests and not one pest group in particular. Most (51%) of the farmers felt that insecticide application should be made from 2 to 7 days after fertilizer was applied, while 11% said it should be done within 1 day of application, with 4% feeling that it should be done up to a week before application. In Guimba, significantly more applications were based on the presence of insects (45% of occasions) than on seeing only damage (20%). Prophylaxis (35%) was statistically intermediate. In Koronadal, applications were similar between presence of insect damage (43%) and prophylaxis (41%) but significantly more than the presence of insects (16%). Across all sites more decisions were made by monitoring (65%) than by prophylaxis (35%). In Guimba where enough seasons data allowed statistical comparison on the seedbed, more decisions were based on prophylaxis (55%) and presence of insects (42%) than on insect damage (20%). 3.5. Pest abundance Koronadal farmers described pest populations more in quantitative (86% of responses) than qualitative (14%) terms and more responses being characterized as damage symptoms (62%) than densities of insects (38%). Qualitative responses centred around the pattern of damage described as being either uneven (8%) or even (6%). Quantitative descriptions included estimating the crop area damaged per parcel in terms of proportions such as a half or third of the area or as actual percentages (27%) (variously 20%, 50%, 70%, etc. of the parcel affected), the number of damage patches per parcel (19%), or the number of parcels having patches of damage (2%). Pest densities expressed quantitatively were in units of number per several hills (26%), number per distance of row (8%), or number per panicle (4%). In Zaragoza estimates of pest abundance were categorized by crop growth stage or pest group and the percentage data is based on responses within each of

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those categories. Most decisions in the seedbed (93% of responses) and vegetative stage (57%) were based on qualitative assessments as were those of leaffolder (59%) and stemborer (84%). Whereas populations of leafhoppers and planthoppers (62%) and rice bugs (100%) were mostly evaluated in quantitative terms. Qualitative responses included those where only the presence of the pest was enough to prompt a spray decision—in the seedbed (worms 18% and moths 10% of responses) and in the field for moths (vegetative stage 1%, leaffolder 12%, stemborer 12%). Qualitative responses were often based on the presence of damage symptoms such as patches (in seedbed 19%, leaffolder 5%, leafhoppers and planthoppers 10%, stemborer deadhearts or white heads 63%), yellowing of the plant (in seedbed 2%), yellowing plants in shade (leaffolder 5%), yellow leaves (leaffolder 2%), whitish leaves (in seedbed 2%, leaffolder 3%), withering leaf tips (hoppers 23%), and as seen in a neighbour’s field (in seedbed 2%). Intensity of damage was assessed as either light or sparse (vegetative stage and leaffolder both 29%) or heavy or dense (16% in vegetative stage, 2% for leaffolder) or increased since the last visit (leaffolder 5%, patches of damage from stemborers 9%) in the field or parcel. Quantitative responses included densities exceeding a threshold based on damage or insects. Pest damage was estimated in units of the field or parcel (o5 patches in vegetative stage 31% and leaffolder 2% and deadhearts and whiteheads 7%, 1–5 patches for leafhoppers and planthoppers 5%, >5 deadhearts and whiteheads 2%, 6–10 patches in vegetative stage 3% and leafhoppers and planthoppers 4%, >10 patches in vegetative stage 3%, half of the field with leaves that had turned white in vegetative stage 2%, o5 damaged leaves in the vegetative stage 2%, >20 damaged leaves for leaffolder 2% and in the seedbed 7%), or rice bug damaged panicles o5 or >5 both 12% or damaged spikelets per panicle for rice bug >5 or o5 both 8%. Insect densities were expressed in numbers per parcel (o5 worms 2% or >5 worms 1% during the vegetative stage, o5 rice bugs 48%). Others used several hills as the unit of measure (o5 31% or >10 6% leaffolder damaged leaves, o5 34% or >15 19% leafhopper and planthoppers, o5 deadhearts or whiteheads 7%).

4. Discussion 4.1. Visitation frequency and reasons for visiting the field when a spray decision made In the pre-Green Revolution era when Filipino farmers grew traditional, photoperiod-sensitive cultivars, field visitations, especially under rainfed conditions, were rare between planting and harvesting. That

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changed with growing of modern varieties under irrigation where Filipino farmers visit at least weekly, the recommended interval to make pest management decisions (Reissig et al., 1986). This study confirmed the finding by Waibel (1986) that, although decision making is more likely to be based on scouting, the main purpose for field visitation is normally for other reasons. Farmers in other Asian countries appear to be more vigilant. van de Fliert and Matteson (1990) found that most (81%) Sri Lankan farmers visited their fields daily, while in Tamil Nadu, India, Sivakumar et al. (1997) found nearly half of farmers monitored their fields for pests every other day. Increased visitation for pest monitoring is warranted when fields are under threat of the brown planthopper which affected the farmers in the studies in Sri Lanka and India. 4.2. Monitoring pattern With an absence of formalized training, farmers in this survey developed their own surveillance methods. Despite the individuality often exhibited, a generalized pattern for making insect control decisions emerged from the surveys (Fig. 1). Surveillance was done by either men or women depending on the task. As women do most of the hand weeding they are more likely to observe pest situations in the early season. Women generally hold the purse strings in a Filipino household and thus take part in the decision making process to purchase insecticide (Warburton et al., 1995). Men visit the field more often than women as they take on more tasks such as water management, monitoring crop growth, pest monitoring, fertilizer and pesticide application, cleaning the dikes, and replanting. Farmers may be prompted to spray their fields as a result of seeing a neighbour do so. Rola and Pingali (1993) found that 67% of Filipino farmers interviewed said at times they spray when a neighbour sprays which was also confirmed in China (Hu et al., 1997). Filipino farmers give the reason to do so is that once a field is sprayed, the smell of the insecticide will drive insects to unsprayed fields, therefore one must spray or suffer the brunt of an infestation emanating from a larger area. Once sprayed, the insecticide, in the view of farmers, does more than kill the pest, it also acts as a repellent against future invasion and build-up (Brunold, 1981). Although it is true that some insecticides such as synthetic pyrethroids act as repellents, they have not been noted to drive pests to unsprayed fields. If all the fields but one are sprayed there is no evidence that insect pests are driven to the unsprayed field. In fact quite the opposite occurs, particularly around the edge of unsprayed fields (Litsinger et al., 1987). Farmers also make decisions based on infestations observed in earlier-planted, neighbouring fields with the belief that the pest situation would quickly worsen in

their fields. Attempts by researchers to utilize earlier planted fields in the development of action thresholds, however, gave erratic results for whorl maggot, defoliators, leaffolder, and stemborer (IRRI, 1988). This was probably because infestations can be highly variable between fields, and although generally true that pest infestations tend to build up over the season, natural enemy activity also increases. Farmers can use infestations seen in an earlier planted fields as a forewarning to monitor more frequently but should spray only after observing high populations in one’s own field. Parcels near the canal tend drain more quickly while those down slope accumulate water, particularly after rains. Through experience some farmers preferentially scouted low lying parcels. This shows good farmer innovation as there is ample evidence to support the farmers’ choice of the wettest parcels as a monitoring site of first choice. A number of rice insect pests are more prevalent in more flooded habitats. The most aquatic is rice caseworm whose larvae have functioning gill-like structures and require standing water for survival (Litsinger et al., 1994). Other species include whorl maggot, yellow stemborer, black bug, and defoliators (Litsinger, 1994). Farmers with a habit of first going to higher lying parcels mentioned doing so for stemborers and leaffolders, but there are no known reports in the literature regarding this microhabitat preference. Leaffolders are known to be more prevalent in shade under trees which are more prevalent in higher lying parcels (Barrion et al., 1991). Another farmer innovation of first monitoring the downwind side of the parcel is also supported from the literature. Caseworm larvae float within cut-off, rolled-up rice leaves thus are blown downwind (Litsinger and Bandong, 1992). Farmers often base their insecticide decision on seeing moths (defoliators, caseworm, stemborers, or leaffolders) flushed out while walking along pathways. This idea of relating flushed moth numbers to field larval infestations was tested in developing action thresholds, but like the earlier planted fields produced erratic results (IRRI, 1988). While walking through fields it is common to flush up clouds of moths producing the expectation of imminent high damage levels. High infestations, however, rarely materialize into the anticipated damage due to the influence of natural enemies. Another insect which prompts farmers to spray is the planthopper Nisia atrovenosa Leth., which feeds on grasses along the bund (dela Cruz and Litsinger, 1986). It can be abundant and when disturbed, swarms land on adjacent rice foliage. Farmers appear not to have a set idea to enter the field during monitoring and will only enter if a decision cannot be made from the edge. Some farmers, short of entering the field, will crouch on the bund and reach into the field to inspect plants for insects or damage. These farmers may tap plants and submerge hills from the bund. Fortunately some of the activities that were the

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Farmer’s field (series of parcels)

Start

See neighbour’s field on way

See neighbour spray

Parcel

Insect pests seek unprotected field

Earlier planted field forewarning

Walk along dike

Flooded / downwind edge of parcel

Low-lying parcel

High-lying parcel

Crouch on dike to inspect plants

Enter parcel

Scan parcel

Cross to other side

Defoliation / foliage colour

Density of patches

Density of damage

Zigzag pattern

Flushing moths

Walk in circles

Tapping / submerging plants

Inspecting plants

Change over time

Fig. 1. Generalized rice insect pest surveillance method of farmers.

primary reason for the farmer to come to the field cause him to enter the field (weeding, cleaning the bunds, or opening the bund to manage water) and thus insect infestations may be detected indirectly. This step-wise decision process was also noted by Waibel (1986) and Goodell et al. (1982). In Sri Lanka, van de Fliert and

Matteson (1990) found that, just as in the Philippines, most of the inspection is done by farmers from the bund. In the authors’ experience in working with Filipino farmer groups during extension exercises, farmers are quite content to observe researchers and extensionists scouting a field while they stand on the dikes. Farmers,

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under this situation, generally need to be coaxed to step into the field. It is believed that farmers are concerned about being seen in a field as a labourer rather than as a manager, particularly those farmers who hire labourers such as in Zaragoza. Those who work in fields are considered lower on the social scale as field work is muddy. A Zaragoza farmer is more likely to enter if he is alone than if a group is present. More Koronadal farmers are prone to enter fields to monitor (43% of occasions) than Zaragoza farmers (11% of occasions), probably because in Koronadal there are fewer landless labourers. There is social pressure for the landless in rural communities to seek work in farmers’ fields when there is a large pool of landless labour and right to harvest arrangements are made (IRRI, 1980). Discussions with farmers have revealed that a number share the belief that one should not enter a rice field once the panicles are formed as plant movement will disturb pollination, reducing grain set. Rice, however, is self-pollinated and disturbing the plants does not affect spikelet density. This belief, however, may be why many farmers are hesitant to enter their field once the panicles have emerged. It was noted that most farmers spray for rice bug based on prophylactic decision making. Of course walking through the field during spraying will disturb the plants but apparently the threat of rice bug is greater than presumed damage caused from walking. Farmers use low water volumes and select nozzles, which project the spray to reduce the number of passes through the field, but as a result severely underdose. Researchers require that monitoring be done from inspecting hills in the field selected along a transect and not from along the borders. Both crossing (Reissig et al., 1986) and zigzag (Shepard et al., 1988) patterns have been recommended by researchers and some farmers follow these same patterns. Farmers related that they sampled more hills when pest populations were high. No farmer interviewed, however, sampled a total of 20 or more hills during any one monitoring day as recommended. In Sri Lanka van de Fliert and Matteson (1990) found that only 7% of Sri Lankan farmers inspect more than two hills of rice upon entering. 4.3. Target pests A formal IPM training program emphasising monitoring and pest and natural enemy recognition was inaugurated on a national basis in the decade after this study (Medina and Callo, 1999). Filipino farmers’ eyesight is generally not good as most are elderly (Matteson et al., 1994). Farmers in the survey who based decisions on seeing insects selected the more mobile and thus more readily seen planthoppers, leafhoppers, and moths. The least observable insects (whorl maggot, defoliators, and leaffolders) were monitored by noting damage. For perceived high-risk situations, such as the

seedbed and ripening stages, prophylaxis was the mainstay. Many farmers understand the various stages of metamorphosis of the common insect pests, but there are still a significant number that do not. Few farmers recognize commonly occurring insect egg stages as being from rice pests such as stemborers, but are more prone to understand larvae are younger stages of moths. A few farmers believe in spontaneous generation in that insects come to the field in the bags of fertilizer or in the water. Caseworms float on water and can enter in this way but few farmers understand that most pests enter by flying. In Honduras some farmers believe that insects come from insecticide containers as well as fertilizer bags (Bentley, 1989). Many studies point to deficiencies among Filipino farmers in recognizing natural enemies. In Leyte a survey by Heong et al. (1994) found that 5% of insecticide applications were directed at lady beetles. A small number of farmers surveyed in this study identified lady beetles as pests. Most farmers acknowledge the existence of natural enemies but these tend to note the larger and more obvious ones such as birds, dragonflies, and spiders (Litsinger et al., 1980). As most Filipino farmers grow vegetables they are familiar with phytophagous lady beetles such as Epilachna philippinensis Dieke thus it is easy to see why some think lady beetles damage rice plants. Also a number of coccinellid species eat the pollen of rice plants and farmers observe this and believe that seed set will decline. As rice is self-pollinated pollen consumption does not affect yield. Filipino farmers also have also been noted to spray insecticide against fungal and bacterial diseases (Marciano et al., 1981). Overuse and misuse of insecticide in rice can exacerbate insect pest problems (Litsinger, 1989). 4.4. Decision mode The mode of decision making varied by site. Farmers had been exposed to two sequential extension messages regarding insecticide decision making. The first in the 1970s when extension messages focused on crop growth stage without monitoring, while in the 1980s farmers were encouraged to monitor and apply insecticide when an action threshold was reached. Kenmore et al. (1987) believed farmers innately preferred the more simple crop stage-based insecticide approach, but since insecticides became increasingly costly, farmers could not afford protection over the entire crop cycle. Farmers limited their usage by applying when the intolerable loss was perceived to be imminent due to economic necessity. Most farmers in this study used a mixture of the three decision modes rather than following any one, but most decisions on the main crop were made after crop monitoring (combining insects and their damage) rather than prophylaxis. Prophylaxis was the mode of choice,

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however, in the seedbed probably because of the highrisk farmers place on damage at this stage. Loss of a seedbed may mean significant delay in planting risk of not receiving sufficient irrigation water. In other studies in the Philippines which focused on the main crop— Litsinger et al. (1980) in rainfed areas and Brunold (1981), Heong et al. (1992), and Rola and Pingali (1993) in irrigated areas—found similar ratio of prophylaxis versus monitoring decision modes. In the surveys of Waibel (1986) in three provinces, 90% of applications were based on monitoring. Similarly van de Fliert and Matteson (1990) found most (79%) Sri Lankan farmers apply insecticide based on pest monitoring. These studies are contrasted by Hu et al. (1997) in Zhejiang, China who found only 17% of farmers applied as a result of field observation. It is interesting that rice bug, one of the most recognized of rice insect pests, is treated mostly on a prophylactic basis. This may be because of its being only one of three insect groups that directly attacks the grains in the field (the other two are stemborers causing whiteheads and armyworms cutting rice panicles). Thus farmers give a high value to rice bug damage as noted in other studies (Litsinger et al., 1982; Heong et al., 1992), as they do not realize that rice plants can greatly compensate from rice bug damage (Litsinger et al., 1998). Differences in decision modes noted between sites could have been due to differences in the pest complexes and outbreak histories across sites as well as differences in perception, the extent and kind of training, and risk that occurred for farmers and their communities. Ethnicity was noted by Litsinger et al. (1982) to explain differences in approaches to pest control. Tagalog farmers in Central Luzon utilize fewer traditional methods and are less superstitious than Illocano or Illongo farmers in Mindanao (Litsinger et al., 1980; Fujisaka et al., 1989). Farmers in Zaragoza and Calauan were mainly Tagalog, while Guimba farmers were a mixture of Tagalog and Ilocano. Koronadal was a mixture of Ilocano and Ilongo ethnic groups. Heong et al. (1994) concluded that individual wetland rice farmers in either the Philippines and Vietnam showed a wide variation in loss assessment from a given pest infestation level. Farmers may vary over time in their motivation to use insecticide. Farmers whose supply of rice has been decimated by a pest outbreak or by inclement weather are more prone to apply insecticide on a prophylactic basis on the next crop when production rather than profit became the central goal (Litsinger, 1993). Among the study sites, Koronadal farmers probably were more conscious of pest outbreaks due to their recent history, which may explain their behaviour to spray more frequently. Despite this they were no more likely to spray based on calendar basis than for the other two sites.

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Some prophylactic insecticide applications may be due to farmers’ thinking they are like fertilizers and follow a strict growth stage schedule in terms of timing and frequency of application. Their attitude seems to be that insecticides are ‘required’ for high yield. For many farmers the term for insecticide translates into ‘medicine’, thus these pesticides are seen to provide a phytotonic affect on the crop. Most Zaragoza farmers, for example, utilized prophylaxis by timing their first insecticide application to their first fertilizer application but monitored the crop for most other applications. On the one hand farmers were astute in linking nitrogen application with increases in insect pest abundance and damage. The farmers’ belief that N causes the rice plant to become soft is true due to enhanced growth reducing the density of protective silica bundles (Litsinger, 1994). Most rice insect pests have been found to increase in abundance, and feeding rates have been found to increase in relation to application of N fertilizer (Litsinger, 1994). Most Zaragoza farmers in the study applied insecticide after fertilizer application, irrespective of pest density. The timing of afterwards rather than before or at the time of fertilizer application allows time for the effect to occur. The farmers’ motive is to protect the now more vulnerable plant. Rola and Pingali (1993) similarly found a significant number of farmers they interviewed (40%) applied insecticide in relation to the timing of the first fertilizer application. Insecticide use based on fertilizer use is rarely justified, however, due to the beneficial effect of fertilizer on plant growth compensation. Therefore, one should not minimize nitrogen usage to rice as a pest management technology. Field trials have shown that nitrogen application increases the tolerance of the rice plant to insect damage, thus significantly raising action thresholds. Therefore even though insect pests benefit, the crop benefits more (Litsinger, 1993). Field trials carried out by farmers form a part of the farmer field school curriculum to demonstrate the beneficial effect of fertilizer in increasing crop tolerance (Matteson et al., 1994). Rubia et al. (1996) found most Indonesian farmers initially did not understand the concept of compensation. Farmers in Guimba, particularly in the dry season, use N rates much above those recommended (averages of 131–152 kg N/ha in 1989–91 dry seasons vs. 90 kg N/ha recommended, unpublished data), and have found by trial and error that insecticide can be substituted by fertilizer. 4.5. Pest abundance Researchers utilize different units of measure for action thresholds based on percentage damaged leaves or insect pest density on a per hill basis (Reissig et al., 1986). Farmers tend to assess insect density and damage

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more in qualitative than quantitative terms often utilizing the whole parcel as the unit of measure. Patches of damage are common units of measurement for farmers. As insect distribution is non-uniform, damage usually occurs in patches. Stemborer deadhearts and whiteheads typically produce observable patches due to eggs laid in masses. Damage by caseworm, armyworm, cutworms, defoliators, leaffolders, planthoppers, and leafhoppers typically occurs in patches as well. Farmers upon return note any change in patch density and size and may base their decision on the rate of change over time often without checking pest identification. The small number of farmers who tap hills to dislodge insects have independently developed this sampling technique utilized by researchers. It is quicker than by direct observation, a method also used. Active hoppers and camouflaged larvae are more readily seen when stuck by the surface tension of water than trying to locate them on the foliage. Farmers slap several hills at once rather than focusing on a single hill as recommended by researchers in order to get a count on a perhill basis. Researchers also count predators on the water surface, not just the pests. Submerging hills to dislodge foliage-feeding larvae is done by a handful of farmers and is an innovative method and does work to cause the larvae to float, especially on a young crop. Most commonly found are defoliators such as semi-loopers which have small bodies and long setae and thus float. Armyworms and cutworms, however, sink due to their larger biomass lack of long setae. It is a good idea to look for the larvae in the field before spraying as if the population has mostly pupated the insecticide will not have the desired effect. Even though the preponderance of insecticide applications in the Philippines was based on monitoring, farmers’ action threshold levels were usually very low. Rola and Pingali (1993), confirming the results of the current study, found that in many cases farmers sprayed when they saw a single insect in the field. Kenmore et al. (1987) found that farmers sprayed upon seeing a few pests as they believed that waiting until threshold numbers occurred would be too late. Farmers told Brunold (1981) that they would rather err by overspraying than under-spraying. Within a group of farmers there exists a wide divergence in sampling techniques. What is interesting is that there is a small number of farmers who appear to be more quantitative in their approach to pest monitoring. From the survey results, pest and damage densities of the common rice insect pests were expressed by some farmers in units used by researchers such as fractions and percentages as well in whole numbers in units of several rice hills, distance of rice rows, and per panicle. In addition leaffolder damage was expressed in terms of numbers of damaged leaves per several hills. Waibel

(1986) found greater numbers of farmers utilizing units similar to researchers. He found that in terms of occasions, farmers made assessments in units of insects per hill (30%), per unit area (18%), individual tillers (15%), per leaf (2%), as well as others using units per field (8%), while 27% were undefined and used the general appearance of the crop.

5. Conclusion The recent formal pest management training involving experiential learning has focused on filling in the gaps of knowledge and clarifying misperceptions identified through studies similar to the current one. This study has shown farmers normally visited their fields weekly but not necessarily for the purposes of pest monitoring, thus farmer field school training has highlighted the need to monitor for pests at least weekly. Farmers understand that more frequent field visits are needed when pest outbreaks have occurred either nearby or in recent years and should be vigilant whenever visiting their fields. Both male and female members of farm families assume different roles and may visit the fields at different times, underscores the need to train both sexes. Farmers can be taught a standardized sampling method to replace cursory inspections made from the field edge. The standard unit is the hill rather than the parcel. Farmer field schools have encouraged farmer entry into the field through example by the trainers as part of the curriculum. Hills should be selected along a transect as pests are not uniformly distributed. Farmers should not spray insecticide before pest monitoring even if (1) a neighbour has sprayed, (2) an earlier planted field exhibits infestation, or (3) fertilizer is applied due to the powerful contravening effect of natural enemies to suppress insect pests and beneficial effect of fertilizer to increase crop tolerance. Monitoring can be done during pollination without harming yield. Training has rightfully focused on improving skills in pest and natural enemy identification. Farmers having difficulty seeing should rely on younger family members to do the scouting. Decisions are made on the ratio of pests to natural enemies encountered, and farmers should learn to recognize natural enemies and understand their role in natural pest control. Reacting to patches of damage seen without learning of the pest responsible via closer inspection may lead to ineffectual control as each pest group has specialized control options. Target life stages should be known in order to direct control efforts at the life stages that cause damage and not moths or pupae which do not feed on the crop. Moths can be thought to be an early warning but are not necessarily an indication of impending damage as egg and larval mortality normally is high.

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The survey found that some farmers have developed novel scouting techniques such as prioritising the wetter low-lying parcels, observing damage in earlier planted neighbours’ fields, submerging and tapping plants, seeking shady locations, and inspecting the downwind side of the field. These techniques were evolved by farmers and were not part of any extension program. Farmers were shown to have keen sense of observation and linking cause and effect. Deducing a carry over effect of systemic insecticide from the seedbed to the main crop was clever and likewise subsequently tested in research trials. Even though quantitative thresholds were concluded to be too complicated for farmers to master (Goodell et al., 1982), the results of this study show that at least some farmers utilized quantitative surveillance methods. All farmers are experimenters, some more than others. But farmers are very different among each other in their knowledge base thus extension programs should seek out the more technically proficient, quantitative, and skilled, those with higher abilities that may have developed more effective monitoring methods to serve as teachers. Farmers can teach other farmers. Experienced crop monitors normally can make rapid assessments of pest incidence without the need of taking counts from a sample of 20–25 hills and calculating averages. Walking through the field is necessary, however, as not all pests can be discerned from the bund. Such experienced people followed the recommended sampling methods when they first started out but as they gained experience could internalize the visual appearances of fields in various stages of damage by gestalt perceptions. Most decisions in an irrigated rice field are no-spray decisions in the Philippines on modern varieties (Kenmore et al., 1987). Only when the pest density approaches an economic injury level would more detailed counting be necessary. Misperceptions regarding yield losses from insect pests should also be pursued in training programs, notably from rice bug. Thus one pest per parcel cannot pose a great threat to a rice crop. Waibel (1986) found that farmers overestimated the yield loss from pests probably by recalling high infestation years rather than taking an average over years. Farmers’ overestimation of yield losses was confirmed by the many surveys of Heong and Escalada (1999). Waibel (1986) also found farmers overestimated the effect of insecticides on pest populations. The effect of farmers’ underdosing is wasteful as field trials using low dosages failed to achieve higher yields or insect control (IRRI, 1988). Farmers are afraid not to use insecticides as a result of propaganda from chemical companies and dealers that heighten the fear of pest outbreaks. Farmers are highly risk averse and subject to manipulation by threats of outbreaks (Waibel, 1986). The unnaturally high yield losses that farmers estimate from normal insect pest

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densities is evidence of that fear as well as their proclivity to spray when seeing few insects per field. Training programs have to counteract this fear factor. Farmers and researchers approach pest control from different perspectives. Researchers can draw on world knowledge through reading literature and attending conferences but have a more reductionist approach, making decisions for a whole field from small samples. Researchers tend to look at components separately and then make conclusions regarding the whole. Farmers have learned by experience relying on information mostly gained on their own with input mainly from their immediate neighbours. Farmers, by and large, are more holistic in their perception (Goodell, 1984; Bentley, 1989). However, a minority were able to extrapolate from pest densities taken from groups of hills and panicles to the whole field and some scouted along transects as would researchers taking diagonal, zigzag, or looping patterns. Both farmers and researchers can learn from one another. The study is unique in that the enumerators were highly experienced in pest identification and came from the study communities. Thus there was not the social distance mentioned by Bentley and Andrews (1991). Farmers were also interviewed frequently during the crop season thus shorter recall occurred with more accuracy of answers. The study was carried out over many years and sites providing a wider array of pests and a more normalized dataset. There were no pest outbreaks during any of the seasons in the study although tungro occurred in isolated areas of Guimba and Koronadal in some years. The selection of multisites to survey showed site effects, particularly between locations and ethnic groups.

Acknowledgements Many locally hired project staff were responsible for conducting surveys and their invaluable contributions are acknowledged. Those assisting in Zaragoza were Catalino Andrion and Rodolfo Gabriel, in Guimba George Romero, in Calauan Mariano Leron, Eduardo Micosa, and Carlos de Castro, and in Koronadal Hector Corpuz, Joseph Siazon, Beatriz Velasco, and Anita Labarinto.

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