Abstract
The brown planthopper, Nilaparvata lugens (Stål)[BPH], is a damaging pest of rice in Asia. Insecticides and rice varietal resistance are widely implemented BPH management practices. However, outbreaks of BPH have been linked to excessive insecticide use—challenging the compatibility of these two management practices. IR62 is a variety with resistance against BPH, the whitebacked planthopper, Sogatella furcifera Horváth [WBPH], and the green leafhopper, Nephotettix virescens (Distant)[GLH]. We compared BPH responses to IR62 and to the susceptible variety IR64 treated with buprofezin, carbofuran, cartap hydrochloride, cypermethrin, deltamethrin, fipronil, or thiamethoxam + chlorantraniliprole. In greenhouse bioassays, cypermethrin, fipronil and thiamethoxam + chlorantraniliprole reduced egg laying on both varieties, and, together with buprofezin, reduced nymph survival to zero. Buprofezin, carbofuran, and cartap hydrochloride stimulated egg laying, and carbofuran increased nymph biomass, but these effects were reduced on IR62. Planthopper populations were ten times higher on deltamethrin-treated rice than untreated rice in a screenhouse experiment. Host resistance failed to buffer against this insecticide-induced resurgence in BPH and WBPH. However, IR62 reduced the effect in GLH. Rice treated with cypermethrin and fipronil had reduced yields compared to untreated controls, suggesting possible phytotoxic effects. We found little evidence of synergies between the two management practices; but host resistance did buffer against the undesirable effects of some insecticides.
Highlights
The brown planthopper, Nilaparvata lugens (Stål)[BPH], is among the most damaging pests of rice in Asia [1]
Fewer eggs were laid on IR64 plants treated with the 7,32 pyrethroids, fipronil, and thiamethtreated with the pyrethroids, fipronil, and thiamethoxamoxam-chlorantraniliprole compared to plants treated with buprofezin, carbofuran, and chlorantraniliprole compared to plants treated with buprofezin, carbofuran, and cartap cartap hydrochloride (Figure 1B)
BPH females tended to lay fewer fewer eggs in many of the insecticide-treated rice plants in the binary choice experiments, eggs in many of the insecticide-treated rice plants in the binary choice experiments, there there were no statistically significant differences between the numbers of eggs laid in were no statistically significant differences between the numbers of eggs laid in treated-IR62 treated-IR62
Summary
The brown planthopper, Nilaparvata lugens (Stål)[BPH], is among the most damaging pests of rice in Asia [1]. BPH occurs throughout the year in tropical Asia where farmers can produce between one and three rice crops per year. The planthopper completes about three generations per crop, thereby, rapidly building up populations in regions of intensive rice production [1,2]. Asia to Korea, Japan, and Northeastern China where large numbers of planthoppers can sometimes overwhelm natural enemies, thereby causing extensive damage to early-season rice crops in these regions [5,6,7]. The management of BPH has relied heavily on two principal methods: firstly, public research has focused on developing rice varieties with resistance
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