Youichi Kobori

Development of an Individual-Based Simulation Model for the Spread of Citrus Greening Disease by the Vector Insect Diaphorina citri

To establish an Integrated Pest Management (IPM) system for crop pest insects and disease, risk assessment of relevant hindrances is necessary. Typically, the data for such risk assessment analysis is collected through a field survey or field experiments. However, the clarification of important factors often requires assessment of the interaction between such factors. Modelling provides a basis for the theoretical description of such interaction, based on field data, and for relevant simulations. We developed a simulation model which estimates the spread of citrus greening disease (Huanglongbing, HLB) by the vector insect Diaphorina citri Kuwayama. Then, we examined the parameters affecting the spread dynamics of the disease, using the model to inform risk assessment. We targeted the area of the Mekong Delta, Vietnam, one of the regions severely affected by the spread of HLB. At the beginning of this chapter, we describe the disease and the vector insect. Then we outline the developmental methodology for the HLB disease-spread estimation model. Finally, we provide suggestions aimed at preventing the spread of HLB, based on the disease-spread estimation results in several situations.

Effects of Selected Insecticides on Matsumuratettix hiroglyphicus (Matsumura), a Vector of Sugarcane White Leaf Disease, and on Two Natural Enemies of the Sugarcane Stem Borer in Sugarcane Fields

Sugarcane white leaf disease, caused by phytoplasma, is the most severe disease that affects sugar production in Thailand. The major vector of this disease is the leafhopper, Matsumuratettix hiroglyphicus (Matsumura). Although several approaches have been employed for management of this vector, they have not been fully successful in eliminating the disease. In the present study, the efficacy of different insecticides in controlling M. hiroglyphicus was evaluated along with their impact on the natural enemies of sugarcane stem borer, which are commonly released in sugarcane fields in Thailand. The study was performed in fields growing tissue culture-raised sugarcane plantlets. Among the different insecticides tested in greenhouse as well as in field, dinotefuran resulted in high mortality of M. hiroglyphicus and had a long residual effect. The impact of dinotefuran on a natural larval parasitoid, Cotesia flavipes (Cameron), and on an egg parasitoid, Trichogramma confusum Viggiani, was observed to be relatively less, and it disappeared rapidly. Hence, our results suggest that dinotefuran is an effective pesticide for the management of M. hiroglyphicus, a key vector of sugarcane white leaf disease.