Occurrence And Chemical Control Of Mirids In Yancheng, Jiangsu Province

Transgenic Bt cotton has shown great promise for the control of the major pest, the cotton bollworm, in cotton field since 1997. Mirids, however, have gradually developed to be the major pests because of the reduced sprays of pesticides, the changes of farming system and cotton varieties. Yancheng area in Jiangsu province is one of the cotton production bases in China. In this paper, the life history, population dynamics, chemicals control, and resistance level to pesticides were investigated to clarify the occurrence and resistance status of mirids. The results can provide useful information for the integrated control and resistance management of mirids.1. The life history of mirids of A.lucorum in Yancheng areaThe green plant bug, A. lucorum occurs five generations a year and lay eggs on host plants to overwinter in Yancheng area. The length of oviposition period is 30 day, which leads to serious generation overlapping of field populations.2. The dynamics of mirids population in transgenic Bt cotton fieldThe dynamics of mirids population is ladder-rising type in Yancheng area. The nymphs and adults of 2nd,3rd, and 4th generation of mirids feed on seedlings, buds, and bolls and cause considerable yield and quality losses of cotton.3. The host plants of miridsMirid bug is a polyphagous insect pest and its host plants arrange widely. The host plants of mirids in Yancheng area include:crops such as cotton, soybean, maize, and et al, fruit trees such as pear, grape, persimmon, and et al, vegetable such as fava beans, peas, garden chrysanthemum, celery, carrots and et al, broad-leaf weeds such as alfalfa, Chinese trumpet creeper, mugwort, vetch, cleavers, field thistle, and et al.4. Chemicals control to miridsToxicity of 4 chemicals to susceptible strains of A. lucorum and A. suturalis was measured in laboratory with glass-vial bioassays respectively. The toxicity of 4 pesticides to mirids was ranked as:fipronil> chlorpyrifos> alpha-cypermethrin> emamectin.The correct mortality of 40% chlorpyrifos EC,1% emamectin EC, and 4.5% alpha-cypermethrin EC to mirids was 85.1%,86.1%,71.0% 1d after sprays,76.8%,72.3% 53.7% 7d after sprays. Chlorpyrifos and emamectin showed fast and long control efficacy to mirids.5. Monitoring of insecticide resistance in mirids populations in Yancheng areaResistance to four chemicals was determined by glass-vial bioassay in 5 field populations of mirids collected from Yancheng area from 2011 to 2013. The results demonstrated that most mirids field populations were still susceptible to chlorpyrifos, emamectin, and fipronil (RR:0.5-5.0 folds). The mirids field populations from 2012 and 2013 had developed low levels of resistance to alpha-cypermethrin (RR:5.5-7.4 folds).