The application of demographic characteristics of Ectropis grisescens (Lepidoptera: Geometridae) in pest risk assessment of IPM.

Ectropis grisescens Warren is one of the most important pests of tea plants. In this study, data on the development, survival, and fecundity of E. grisescens were collected at 15, 22, and 32 °C and analyzed by using the age-stage, two-sex life table. At 15 °C, the duration of the preadult period of E. grisescens was significantly prolonged (81.06 days), with high mortality (69.0%), and the proportion of emerged female adults was extremely low (7.0%). At 32 °C, the preadult period was significantly shortened (29.12 days), with high preadult mortality (74.0%), and a low proportion of emerged female adults (15.0%). At 22 °C, with low preadult mortality (24.0%), and a high proportion of emerged female adults (26.0%). The overall effects of the shorter preadult duration, higher preadult survival rate, higher proportion of emerged female adults, higher fecundity (F = 350.88 eggs/♀), and higher net reproductive rate (R0 = 91.23 offspring/individual) at 22 °C resulted in the highest values of the intrinsic rate of increase (r = 0.1054 days-1) and finite rate of increase (λ = 1.1112 days-1). Computer simulation showed that E. grisescens populations can increase much faster at 22 °C than at 15 and 32 °C. The weighted population size and cumulative weighted insect-days provided the dynamics necessary for estimating the damage potential of E. grisescens in devising economical pest management programs. Our results demonstrate that populations of E. grisescens were able to develop at a broad range of temperatures and adapt to the high temperatures. These finding can be utilized to improve the management of E. grisescens.

The impact of cover crops on the predatory mite Anystis baccarum (Acari, Anystidae) and the leafhopper pest Empoasca onukii (Hemiptera, Cicadellidae) in a tea plantation.

BACKGROUND: Empoasca onukii, the tea green leafhopper, is a key pest of tea whose control often requires the extensive use of insecticides. As a predator of the tea green leafhopper, the mite Anystis baccarum is a potential biological control agent worldwide, though little is known about how intercropping cover crops can impact its suppressing effect on E. onukii. Therefore, we conducted a field experiment to investigate how the relationship of the abundance of the predatory mite and its leafhopper prey is influenced by two different cover crops and a manually weeded inter-row treatment as a contrast to naturally growing vegetation in a tea plantation in China. RESULTS: The abundance of A. baccarum was significantly higher in tea canopies of intercropped treatments than in canopies over natural ground cover. Litter samples showed higher abundances of A. baccarum when tea was intercropped with Paspalum notatum than with natural ground cover in the first year of treatment. The abundance of E. onukii in tea canopies was higher over the bare ground treatment in the first year but the opposite was observed in the second year. CONCLUSIONS: Results suggest that the abundance of A. baccarum in a tea plantation is influenced by intercropping and it can affect its leafhopper prey, albeit with varying levels of suppression. For informing biological control and suppression of pests, long-term experiments are needed to investigate the interactions of both pest and predator with cover crop treatments. © 2019 Society of Chemical Industry.