The Effects Of Host Plants On The Growth And Development,Population Dynamics And Cold Resistance Of Loxostege Sticticalis Linnaeus

Loxostege sticticalis Linnaeus is a worldwide pest that has been plagued in the northwest,north and northeast of China,and caused huge economic losses.Due to changes in crop planting structure in China,Studying on the biological characteristics and cold resistance of L.sticticalis on different host plants would help us monitor the dynamics of pest population,and provide theoretical basis for forecasting and scientific prevention.The growth and population dynamics of L.sticticalis in seven host plants were analyzed by the age-stage two-sex life table method.It was found that the developmental duration,reproductive capacity and life table parameters of L.sticticalis in different treatment groups were different.The larvae of the pigweed treatment group had the shortest development period,(only 13.95 d);the female moth had the longest spawning period(10.32d);the highest number of laid eggs,the average number of female moths spawned 226.03;the net value of population(R0),the intrinsic growth rate(r)and the weekly growth rate(?)are 84.01,0.111,and 1.17,respectively,which are maximum;the average generation period(T)is the shortest,only 39.96d,indicating that pigweed is the most suitable host plant for L.sticticalis.In addition,the indexes of the pigweed-wheat group and the pigweed-sunflower group were stronger than the corresponding wheat group and sunflower group,and the population dynamics within 90 days according to the life table parameters of the population indicated that the alfalfa was compared with the other three host plants.It is most conducive to the growth of the population of L.sticticalis.Using the indoor insect flying computer data acquisition system,the flight ability of the 3-day old adults was hoisted for 10 hours after feeding on 7 host plants.The results showed that compared with other treatment groups,the flight distance,flight speed and strong flight(flying distance greater than 10km)of the L.sticticalis adults in the pigweed treatment group were significantly higher.The indicators of the pigweed-wheat group were significantly stronger than that of the wheat group.These results indicated that the host plants influence the flight ability of the adult grasshoppers,and pigweed was the suitable food source for grasshoppers flying.According to the results of four midgut-digestive enzyme activities of the larvae of the grasshoppers in the seven groups of host plants,there were significant differences in midgut-digestive enzymatic activity among grasshoppers at different stages.Digestive enzyme activity increased with age,with the IL had the lowest digestive enzyme activity and 5L reached the highest.There was also a significant difference in the activity of digestive enzymes in the midgut of the same age in the 7 groups of host plants.The enzymatic activities of Trypsin,CL and AMS in the larvae on the pigweed treatment group were higher than other group.When the larvae transferred to the host plants,their corresponding midgut digestive enzyme activities changed,which further indicated that the host plants could affect the enzymatic activity of the midgut digestive enzymes.According to the changes of activity of the Trypsin,CL and AMS,the effects of host plants on the growth and development of grasshopper larvae were basically the same,indicating that the effects of host plants on the growth and development of L.sticticalis were achieved by changes in the activities of these digestive enzymes.The SCP and FP of L.sticticalis on seven host plants were determined.The results showed that under the condition of non-diapause,there were significant differences in the SCP and FP between grasshoppers of same stage on different hosts,indicating that the host plants had significant effects on the cold resistance of L.sticticalis.And in each group of host plants,there were significant differences in the SCP and FP of L.sticticalis at different development stages.In the five development stages of the larval,the SCP and FP of the seven groups of host plants showed that the 5th instar larvae were the highest and the 5-days pupa were the lowest.The cold resistance of pupa was stronger than that of larvae.Host plants affect the growth and development of L.sticticalis and the ability of adults to fly.Feeding suitable hosts,its growth rate is fast,survival is high,population growth rate is large,and adult flying ability is strong.The effect of host plants on the growth and development of L.sticticalis larvae is determined to some extent by the activity of intestinal digestive enzymes.Suitable host plants can enhance the cold resistance of the L.sticticalis larvae..