by
M.M. Escalada, Visayas State University, Leyte, Philippines,
L Wang, Q. Yuan, D. Cai, Hainan University, Hai Kou, China and
K.L. Heong, International Rice Research Institute, Los Baños, Philippines

Farmers being interviewed by trained student enumerators.

In making pest management decisions, farmers always face uncertainty and often adopt the bounded rationality approach. In this approach, as opposed to unbounded rationality, farmers will tend to “satisfice” rather than “optimize.” Satisficing, a combination of sufficing and satisfying, is a word of Scottish origin to characterize decision making in conditions of limited time, knowledge, and computational capacities using simple rules or “Heuristic”, a term to refer to an informal rule-of-thumb used in decision making. Heuristics are developed through experience and guesswork about possible outcomes and may thus have inherent faults and biases. Research to understand farmers’ current heuristics and reasons for their adoption will help scientists frame alternative heuristics that improve outcomes (Escalada and Heong, 2012).

In an earlier work on the rice leaffolder, Cnaphalocrocis medinalis (Guenée), a simple rule-of-thumb or ‘heuristic’ was which was in conflict with prevailing belief that spraying was necessary, was communicated to farmers and they were encouraged to test the rule. The heuristic stated: ‘In the first 30 days after transplanting (or 40 days after sowing), leaffolder control is not necessary’.

In this leaffolder example, farmers sprayed insecticides to control the larvae (often called “chuang” or “worms”) because of they are highly visible.  Farmers tend to strongly believe that leaf damages will lead to yield loss and that the worms will multiply quickly and thus need to be killed immediately. These beliefs might stem from farmers overestimating potential losses and their loss aversion behavior.

In decision theory, loss aversion is the tendency of people to strongly prefer avoiding losses to acquiring gains. The phenomenon was first described by Amos Tversky and Daniel Kahneman (1974) when they developed Prospect Theory.

In Hainan, we surveyed 411 rice farmers in December 2010-January 2011 and found that farmers would apply insecticides regardless of whether pests were present or can potentially cause yield loss. About 58% of the sprays had no specific targets, 13% were targeted at leaf folders, 19% at planthoppers and the remaining 10 % of the sprays were targeted at stem borers and minor pests like “general worms”. Sixty-three (63%) percent of the farmers strongly thought that “all insects in rice fields are harmful” and 83% of the farmers believed that insecticides MUST be used to achieve high yields.

Relationship between farmers’ yields and number of insecticides applied. Means and std error bars.

When we plotted farm yields with the number of insecticide sprays used, we obtained no significance (F = 2.20; p = 0.139) and a negative regression (coefficient = – 0.081). Farm yields varied from 3 to 12 ton per ha, while number of insecticide sprays ranged from zero to 12. Two farmers sprayed more than 10 times and their yields were less than 4 tons/ha, while the 6 farmers who did not spray anything averaged 5 tons/ha. Farmers that had higher sprays seem to have higher variability.

Reference

Escalada, M.M. and Heong, K.L. (2012). Using decision theory and sociological tools to facilitate adoption of biodiversity-based pest management strategies. In Gurr, G.M., Wratten, S.D., Snyder, W.E., Read, D.M.Y. (Eds). Biodiversity and Insect Pests: Key Issues for Sustainable Management. John Wiley & Sons, Ltd., UK. Pp 199 – 213.

Tversky A. & Kahneman D. (1974) Judgment under uncertainty: heuristics and biases. Science. 185,1124-1131.