Search

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.

Fall armyworm is recognized as one of most highly destructive global agricultural pests. In January 2020, it had first invaded Australia, posing a significant risk to its biosecurity, food security, and agricultural productivity. In this study, the migration paths and wind systems for the case of fall armyworm invading Australia were analyzed using a three-dimensional trajectory simulation approach, combined with its flight behavior and NCEP meteorological reanalysis data. The analysis showed that fall armyworm in Torres Strait most likely came from surrounding islands of central Indonesia on two occasions via wind migration. Specifically, fall armyworm moths detected on Saibai and Erub Islands might have arrived from southern Sulawesi Island, Indonesia, between January 15 and 16. The fall armyworm in Bamaga most likely arrived from the islands around Arafura Sea and Sulawesi Island of Indonesia, between January 26 and 27. The high risk period for the invasion of fall armyworm is only likely to have occurred in January–February due to monsoon winds, which were conducive to flight across the Timor Sea towards Australia. This case study is the first to confirm the immigration paths and timing of fall armyworm from Indonesia to Australia via its surrounding islands.