Temporal And Spatial Distribution, Life Table Analysis And Population Simulation In Apolygus Lucorum (Meyer-diir)(Heteroptera:Miridae)

The widespread adoption of Bt cotton has drastically reduced the need for broad-spectrum insecticides for Helicoverpa armigera Hubner but has resulted in an increased population density of mirid bugs. Mirid bugs (Heteroptera:Miridae) have now become key insect pests of cotton fields in northern China.The mirid bug Apolygus lucorum Meyer-Dur has become a prevalent pest of several crops in China, particularly cotton Gossypium hirsutum L. A. lucorum is a polyphagous insect pest and its life cycle involves seasonal movement between host plants. In the present paper, we studied the distribution pattern and sampling method of A. lucorum, natural population life table in cotton field, transfer host plant and developed a computer model. Our work will help us to simulate the population dynamics of A. lucorum. The main results were summarized as follows.In order to understand the spatial distribution pattern of this A. lucorum, its population aggregating indexes on cotton field were calculated based on the related index formulae. The results showed that the spatial distribution pattern of the adult, nymph and whole A. lucorum population belonged to gathered distribution in seeding stage. The spatial distribution pattern of the adult and whole population belonged to random and the nymph belonged to gathered distribution in flower stage and boll stage. Adult stay mainly on leaf and nymph stay mainly on bud and leaf. Whole plant survey is the effectively sampling methods. The regression equation of whole plant survey and bud survey is y=0.74x+5.81(R2=0.69).The cotton field life table analysis showed that egg hatch rates were from45.1%to50.1%and nymph survival rates were from33.78%to37.36%. The main mortality across all stages was attributed to predation, rainfall, parasitism and incomplete moulting, respectively. Across all factors, the highest mean rate of marginal mortality was observed in the first nymph followed by the egg, second-, third-, forth-and fifth-nymph respectively. Key factor analysis revealed that predation and rainfall were the major mortality factor contributing to generational mortality for nymphs. The k mortality factor was attributed to rain for1st and2nd instar. The k mortality factor was attributed to rain and predation for3rd instar. The k mortality factor was attributed to predation for4th and5th instar. Across stages, highest irreplaceable mortality rates were observed in the eggs and the first-nymph. The other stage had relatively low rates of irreplaceable mortality.Stable isotope analysis was used to investigate the differences between host plant use and transfer in different host plants of A. lucorum in northern China. The stable isotope analysis revealed that the δ13C values were significantly different between adults reared on C3and C4photosynthesis type plants. We found that A. lucorum raised in C3plants gave813C values ranging from-29.87to-24.16, compared with-13.6to-12.8for those raised on C4plants. Nymph food had a significant influence on the δ13C value of the adult. The adult food had no significant influence on the δ13C values. The C3plants were the main host plant and C4plants were used for3rdand4th generation of A. lucorum. The mean values,0.19%,2.43%and5.74%of adults were categorized as having developed on C4plants for the2nd,3rd and4th generation of A. lucorum, respectively. The stable isotope analyses also suggested that the δ13C value distribution was significant different between different sites. The proportions of C4plants that developed A. lucorum for the3rd and4th generations no significantly correlated with the planting pattern. In conclusion, maize (Zea mays L.) is the preferred host from August to September and this observation appears to play a role in the season-long dynamics of A. lucorum infestation in cotton field areas.A computer model is developed to simulate the population dynamics of A. lucorum over a wide area in northern China. The area considered covers12provinces where serous outbreaks of A. lucorum have been observed. In this mode, pest development is driven by local ambient temperature, and adults short distance migratory behavior and select preferred hosts for ovipostion within a region. Five types of host including cotton, cotton, soybean, fruit tree and weed are considered in this model. Survival rates of eggs and nymph are based on life-table data and simulated as a function of host type, host phenology and temperature. The incidence of diapause depends on temperature and photoperiod experiment during the nymph stage. Survival rates of non-diapause egg and overwinter egg survival are fixed value. Insecticide is applied when population density exceeds the economic threshold on a host crop within a region. Comparisons of model output with field population data indicated that our model reflects the pest population dynamics and more than80%cases were successful simulation. This model could potentially be used for testing pest control strategies in northern China.