Study on the components of rice integrated pest management: insect repellent, endophytic entomophatogenic fungi, and risk assessment of insecticides in rice ecosystem

Food security and sustainable food insufficiency are the ultimate goals for farmers, governments, and research institutions. Rice production development and intensification is influenced by demand of increasing population and is threatened by a pests and abiotic stresses. Use of synthetic chemicals has been the foundation for crop protection and production systems and has benefited rice production for many years. However, the excessive use and misuse of these chemicals particularly pesticides have resulted to adverse effects in human and environmental health. These concerns regarding the use of synthetic pesticides guided this study to innovate and combine existing integrated pest management technologies to find new ways of controlling insects and improving growth of rice which are safe humans and ecologically-acceptable. Technologies include the combination of using methyl eugenol as a botanical pesticide, entomophatogenic fungi (EPF) as endophytes, and selective insecticide effects on parasitoids. Methyl eugenol is a phenolic compounds commonly produced by spices and medicinal plants wit a paricular characteristics of attracting some insects speciesand medicinal plants with a particular characteristics of attracting some insect species and repelling others. In a laboratory study, significantly fewer brown planthoppers (BPH) were found inside small cages treted with methyl eugenol compared to the control, indicating s repellency effect of methyl eugenol on BPH. This effect was not as clearly demonstrated in a larger scale represented by greenhouse study. Numerically more individuals of BPH were recorded on the untreated plants compared to methyl eugenol-treated plants, however there was no statistically significant difference between the two treatments. Plants are occupied by microbes. Plant-microbe interactions can either cause the host to acquire disease or to gain positive effects represented by fungal endophytes. For the first time, entomophatogenic fungi was proven that they acn established in rice for possible insect defense and growth stimulation. Results showed that EPF as endophytes can increase plant growth, can negatively influence feeding preference of BPH, and does not affect predation rate of natural enemies. Lastly, this study highlighted the relative toxicity of Scotinophara coarcata and its egg parasitoid, Telenomus triptus using risk assessment methods. Some of the tested active ingredients are listed in U.S. Environmental Protection Agency's (EPA) Conventional Reduced Risk Pesticide Program as reduced risk/alternative pesticides. Risk assessment on each active ingedient was conducted using selectivity ratio on S. coarcata and T. triptus and probit substitution methods. Of all tested active ingredients, the most toxic of T. triptus were apinosad, tebufenozide and indoxacarb with respective toxicity ranges of 128-790, 132-234, and 12-39 times more susceptible to the rice black bug. It was found that all tested active ingredients were non-selectiveand more selective to T. triptus with selectivity ration ranging from 0.001 (spinosad) to 0.667 (fenobucarb) except to one population of S. coarctata on which fipronil (1.275) was more toxuv to it than on T. triptus. All probit substitution values were above 90% (94-99%) which was an indication that the active ingredients were more toxic to the parasitoid. The results emphasize the need to conduct risk assessment on natural enemies commonly found in rice fields during pesticide registration phase. Furthermore, it calls into question the 'reduced risk' designation of some active ingredients as pertain to tropical rice ecosystems.