Alternately Rearing with Susceptible Variety Can Delay the Virulence Development of Insect Pests to Resistant Varieties

Abstract

Resistant crop varieties can usually decrease the population density of insect pests; however, they can also easily cause the occurrence of highly virulent pest populations when repeatedly grown. Whether herbivorous insects feeding intermittently on a susceptible variety affects their subsequent virulence has rarely been investigated. In this paper, we examined the variations in the virulence of the brown planthopper (BPH), Nilaparvata lugens (Stål) (Hemiptera: Delphacidae), by alternately rearing three resistant rice varieties, Mudgo, ASD7, and Rathu Heenati, with a susceptible rice variety (TN1) in indoor experiments. The results showed that, while the susceptible rice variety was used in alternate rearing for several generations, the BPHs exhibited a higher intrinsic rate of increase (rm) and were identified as less virulent to all three resistant varieties. Such virulence reduction by experience with a susceptible variety could delay the progression of resistance-breaking toward resistant varieties. The results suggested that careful alternation with susceptible varieties in fields is a potential method for pest variety-resistance management.