Abstract
The green mirid bug Apolygus lucorum is a regional pest of multiple crops in northern China, and the survival and development of diapausing eggs during winter plays an important role in the population dynamics of this species. The effect of water on the survival and development of A. lucorum eggs was investigated using laboratory-induced diapause. Diapausing eggs were exposed to various humidity regimes under three conditions: (1) termination of diapause with exposure to warm long-day (WLD) conditions (i.e., 26 ± 1°C and 75 ± 5% relative humidity (RH) under a photoperiod of 16 hours light and 8 hours dark), (2) termination of diapause by chilling at 4°C, or (3) during the post-diapause stage, i.e., from transfer to WLD conditions after chilling, until the hatching of nymphs. The results indicate that water availability is crucial for the post-diapause resumption of development of A. lucorum. However, exposure to excessive moisture was detrimental, as indicated by a decrease in diapause termination rate and a prolonged pre-hatching period of diapausing eggs, compared to limited moisture conditions. This implies that both too dry and too humid environmental conditions would suppress survival and postpone hatching of overwintered A. lucorum eggs, and might explain why this pest has not caused severe damage in either southern or western China where the respective climates are very humid or dry.
Highlights
Commercialization of transgenic Bt (Bacillus thuringiensis) cotton has successfully controlled the cotton bollworm, Helicoverpa armigera (Hübner) in northern China, and caused a sharp decline in the use of broad-spectrum insecticides
When diapausing eggs of A. lucorum were kept consecutively under warm long-day (WLD) conditions, diapause eventually terminated and the nymphs hatched, but the diapause termination rate and prehatching period were influenced by watering regimes (Table 1, Fig 2)
The pre-hatching period of the diapause/post-diapause stage for both treatments (Table 1, Treatments A and I) was significantly longer than that for other treatments except for the treatment with watering once on day 95 of incubation (Table 1, Treatment H). These results indicated that water is crucial for the survival and diapause/post-diapause development of diapausing eggs of A. lucorum
Summary
Commercialization of transgenic Bt (Bacillus thuringiensis) cotton has successfully controlled the cotton bollworm, Helicoverpa armigera (Hübner) in northern China, and caused a sharp decline in the use of broad-spectrum insecticides. The Effect of Water on Survival and Development of Diapausing Eggs the dominant species on Bt cotton, jujube tree Ziziphus jujuba Mill., grape tree Vitis vinifera L. and other crops in northern China [5,6,7]. This pest overwinters as diapausing eggs laid inside tissues of host plants, predominantly jujube trees, grape trees and weeds adjacent to cotton fields [6,7,8]. Understanding the survival and development of diapausing eggs, and how environmental factors influence the hatching process, is critical for accurate forecasting of the population dynamics of this pest and for providing guidance for control practices
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