K.L. Heong

Quantifying rice farmers' pest management decisions: beliefs and subjective norms in stem borer control

The paper introduces the pest belief model and Fishbein and Ajzens theory of reasoned action to analyze farmers’ decisions in stem borer management. Farmers spent an average of

Changes in rice farmers’ pest management in the Mekong Delta, Vietnam

39/ha (median

Mechanisms of compensation of rice plants to yellow stem borer Scirpophaga incertulas (Walker) injury

18) on insecticides believing that if they had not controlled an average loss of 1004 kg/ha or

Genetic variation among Asian populations of rice planthoppers, Nilaparvata lugens and Sogatella furcifera (Hemiptera: Delphacidae): mitochondrial DNA sequences

402 (median 592,

Population dynamics of plant- and leafhoppers and their natural enemies in rice ecosystems in the Philippines

237) would occur. Farmers’ estimates of the worst attack averaged 19 white heads/m2 (median10) with the associated average loss of 1038 kg/ha or

Mechanisms for flowering plants to benefit arthropod natural enemies of insect pests: Prospects for enhanced use in agriculture

415 (median 592,

Ants in tropical irrigated rice: distribution and abundance, especially of Solenopsis geminata (Hymenoptera: Formicidae)

270), implying that farmers’ decisions were guided by the worst attacks. Perceived benefits from insecticides were directly related with farmers’ insecticide use and perceived severity. Perceived susceptibility was also high, with 59% of farmers believing that a loss of 450 kg/ha would be “extremely or very likely”. Farmers believed insecticides could destroy natural enemies but placed only moderate importance to conserving them. Health was believed to be very important but farmers had mixed beliefs that spraying could bring about poor health. This study also provides evidence suggesting high peer pressure on farmers’ spray decisions directly influencing perceived benefits from sprays, insecticide spending and spray frequency.

Impact of nitrogenous-fertilization on the population dynamics and natural control of rice leaffolders (Lep.: Pyralidae.

Abstract Between 1992 and 1997, two insecticide reduction interventions were introduced to farmers in the Mekong Delta, the media campaign to motivate farmers to experiment whether early season spraying for leaf folders was necessary and the farmer field schools (FFS). The media campaign reached about 92% of the 2.3 million farmer households in the Mekong while the FFS trained about 108,000 farmers or 4.3%. Farmers’ insecticide use, early season sprayings and pest management beliefs reduced markedly over the 5-year period. Spray frequencies changed from 3.4 to 1.0 sprays per season, a reduction of 70%. Less farmers sprayed in the seedling, tillering and booting stages changing from 18, 65 and 45%, respectively to 1, 12 and 22%, respectively. Changes in farmers’ beliefs were significant, with the belief index reducing from 11 to 6.7. There were significant differences between farmers reached by media and trained by FFS, farmers reached only by the media, and those not reached by either intervention. Spray frequencies were 0.5, 1.2 and 2.1, respectively and similar differences in early season spraying and beliefs were observed. It is evident that the two interventions, media and FFS, played complementary roles in significantly changing farmers’ beliefs and insecticide use in the Mekong Delta.

Effects of herbicides on rice resistance and on multiplication and feeding of brown planthopper (BPH), Nilaparvata lugens (StÅl) (Homoptera: Delphacidae)

Abstract Field and greenhouse experiments were conducted to investigate the impact of stem borer injury on the physiology and yield response of irrigated rice. The compensation mechanisms investigated included increased tillering, increased percentage of productive tillers, and increased grain weight. Assimilates were translocated from stem borer-injured tillers to healthy tillers. The photosynthesis rate of green leaves in stem borer-injured tillers increased. The results indicate that all these mechanisms can be employed by rice plants in response to stem borer injury. The implications for rice pest management, including breeding for cultivars tolerant to stem borer injury, nitrogen fertilisation to encourage plant compensation, and an increase in the economic threshold for stem borers, are discussed.

Selection of nectar plants for use in ecological engineering to promote biological control of rice pests by the predatory bug, Cyrtorhinus lividipennis, (Heteroptera: Miridae).

Many species of insects associated with cultivated rice do not over-winter in Korea and Japan, but migrate into these areas each year. To understand better the origins of these immigrations as well as the geographic structure of rice pests in Asian rice growing regions, intraspecific variation in two species of delphacid planthoppers, Nilaparvata lugens (Stal) and Sogatella furcifera Horvath, was examined. An 850 base pair region of mitochondrial DNA cytochrome oxidase-I (COI) was sequenced from a total of 71 individuals collected from 11 localities in seven countries: Korea, Philippines, China, Bangladesh, Malaysia, Vietnam and Thailand. In N. lugens, three haplotypes were found and all populations sampled shared a dominant haplotype. Localities in Korea contained two haplotypes and localities in China and the Philippines contained three. However, in samples from the Indochina peninsula no variation was detected either within or between populations, consistent with a hypothesis of regular migration and gene flow. These populations did not contain some haplotypes found in Korea, suggesting they were not the source of yearly immigration into Korea and, by extension, Japan. Populations from China did share haplotypes with Korea, which was consistent with the hypothesis that China was the source for yearly immigration into Korea. There was insufficient resolution to distinguish among populations in China. For N. lugens, the data suggested that populations south of the Red River Valley in Vietnam experienced regular mixing and were distinct from populations to the north which contributed to yearly immigrations. In S. furcifera, there was less differentiation among populations. Two haplotypes were found in all populations except Malaysia. The results for both species were consistent with seasonal weather data and indicated that more detailed analysis of DNA sequence data will be fruitful.