Effect Of Soil Moisture On The Growth, Survival And Reproduction Of Cotton Bollworm, Helicoverpa Armigera (H(?)bner)

The influence of soil moisture on the growth, survival and reproduction of cotton bollworm (Helicoverpa armigera) were studied by simulated experiments. The biological habits of entry, pupation and emergence were carefully surveyed and the fluctuating asymmetry (FA) of the tested moths was measured. The main points of the results are as follows:1.The entry route of the larvae and the emergence tunnel of the moths were not the same way. The shape of the whole tunnel of pupation was like a letter 揢?2.The soil moisture exerted little effect on the rate of entry and pupation but significant effect on the rate of normal emergence which would be decrease with the increasing of soil moisture. The 2nd, 3rd and 10th day after entry are the key periods largely affected by soil moisture when the emergence rate were approximately only about 60%, 30% and 30% respectively. The saturate soil moisture experienced by the bollworm entered into soil would produce an exterminatory effect on emergence of the moths (the emergence rate was less than 7%), but relatively less influence before entry (the emergence rate was about 67%).3.Soil moisture could show different effects on the duration of the pupae at different developmental stage. At the 5th day and 8th day after got into soil, the duration of the pupae would be prolonged with the soil moisture increasing. While from the 10th day after entry to emergence, the duration could be shortened with the soil moisture raised.4.The 3rd, 5th and 8th days after entry were the key stages that the moth longevity was affected by soil moisture. During these periods, high soil90moisture could cut down the survival ability and reduce the longevity from 13 days of CK to 7days, and the time that 50% moths died would be advanced about 6? days.5.High soil moisture during pupation could reduce the reproduction capacity of the moths. At the 3rd, 5th, 8th and 10th day after entry, soil moisture from 40% to 80% reduced the mating rate obviously. Their ovarian development would be retarded when soil moisture was more than 80%. From the 8th day after entry to emergence, soil moisture more than 60% made the hatch rate of the next generation eggs reduced significantly, in which the 10th day was the most sensitive stage.6.At the end of pupation and in the periods of emergence and getting out from soil, soil moisture above 40% relative moisture could obviously reduce the number of population, and had no advantage on the population dynamics.7.Soaking soil (simulating rainstorm to make the soil moisture saturation and let it evaporate naturally till the soil moisture become 40% then kept this level to emergence) showed little impact on the rate of entry and pupation, but obviously affected the rate of normal emergence except the treatments before entry. At the 2nd, 3rd and 10th days after entering soil, the soaking soil reduced the rate of emergence significantly. The duration of the pupation prolonged significantly when soil soaking at the 2nd, 3rd. 8th and 10th day after entry, mating capacity obviously decreased at the 3rd day, the survival ability of moths reduced significantly at the 5th day, and the oviposition rate decreased at the 10th day. Soil soaking at the 3rd day after entry could significantly affect the hatch rate of the eggs. Besides soil soaking during the periods of pre-pupation and emergence had significant effect on the population dynamics, and obviously reduced the number of population.8.The moths showed significant FA when soils were soaked at the 2nd, 3rd and 10th day after entry. Before entry and at the 2nd, 3rd and 5th day after entry, the moths did not appear FA under different soil moisture. But from the 8th day after entry to emergence, the FA of the moths significantly increased when soil moisture was more than 80%.