As an invasive weed, Mikania micrantha Kunth has caused serious damage to natural forest ecosystems in South China in recent years. Mikania micrantha wilt virus (MMWV), an isolate of the Gentian mosaic virus (GeMV), is transmitted by Myzus persicae (Sulzer) in a non-persistent manner and can effectively inhibit the growth of M. micrantha. To explore the MMWV-M. micrantha-M. persicae interaction and its impact on the invasion of M. micrantha, volatile compounds (VOCs) emitted from healthy, mock-inoculated, and MMWV-infected plants were collected, and effects on host preference of the apterous and alate aphids were assessed with Y-shaped olfactometers. Gas chromatography-mass spectrometry (GC-MS) analysis indicated that MMWV infection changed the VOC profiles, rendering plants more attractive to aphids. Clip-cages were used to document the population growth rate of M. persicae fed on healthy, mock-inoculated, or MMWV-infected plants. Compared to those reared on healthy plants, the population growth of M. persicae drastically decreased on the MMWV-infected plants. Plant host choice tests based on visual and contact cues were also conducted using alate M. persicae. Interestingly, the initial attractiveness of MMWV-infected plants diminished, and more alate M. persicae moved to healthy plants. Taken together, MMWV appeared to be able to manipulate its plant host to first attract insect vectors to infected plants but then repel viruliferous vectors to promote its own dispersal. Its potential application for invasive weed management is discussed.

The genetically engineered insect-resistant crops, Bt crops, were first commercially grown in 1996 and adopted in different countries. The economic benefits of Bt crops are reducing the use of insecticides and more safe to environment, however, development of resistance by insects might reduce their efficacy. Unfortunately, the field population evolved resistance to different Bt toxins and the number of resistant species is going to increase, which threat the continuous success of Bt crops. Thus, understanding the Bt resistance mechanisms, including the molecular basis of resistance is important for well-resistance control in Bt crops. This review paper displayed the mechanisms of insect pests resistance to Bt crops and appropriate strategies to delay and manage the resistance in Bt crops. Key words: Field-evolved resistance, molecular mechanism, resistance to Bt toxins, resistance management strategies, transgenic crops.