Investigation On The Occurrence To Primary Pests And Their Control On Mulberry Trees In Rugao Area

During the growth process,mulberry is often infected by various pests,which would affect its growth,reduce the yield and quality of its leaves,and reduce the production of silkworms.There are many pests in mulberry fields,some of which have seriously occurred in recent years.These pests are causing serious damage to local mulberry fields,being a major threat to the production of silkworms.In this study,the occurrence of the main mulberry pests in Rugao City was investigated;the control methods were studied and applied based on the occurrence and biology of these pests.The main results are as follows:1.According to the investigation in recent years,the main pests in mulberry fields of Rugao City include mulberry pyralid,mulberry looper,mulberry weevil,Spodoptera litura,mulberry whitefly,mulberry thrip,and red spider,etc.2.The occurrence patterns of major pests are as follows:(1)In Rugao,the mulberry pyralid has five generations per year and its larvae of fourth generation will compete with mid-autumn silkworm on mulberry leaves,resulting in the decrease of both quantity and quality of mulberry leaves.The larval stage of each generation is in June,July,August and mid-September with overlapping generations,and the fourth generation is most harmful.The hatchability of mulberry pyralid will increase in wet weather,while the larvae are more harmful when it's hot and dry.(2)The mulberry looper has 3-4 generations per year in Rugao,damaging the spring buds in overwintering generation and injuring the autumn leaves in the third generation.A warm winter would help the larvae to survive the winter;a hot and wet weather after May would help the adults to emerge and help the eggs to hatch;they would cause serious damage in early-spring and autumn.(3)Spodoptera litura has 4-5 generations per year in Rugao,and its pupae would overwinter in soil(3-5 cm beneath the surface);when the soil is firm,they would stay in the fallen leaves or on the ground.(4)The mulberry weevil has one generation per year,overwintering mainly by adults in pupation cave;it likes to feed in the half dead piles.3.Special weather conditions can greatly affect the occurrence of the pests.The high overwintering temperature will reduce the mortality of pests,resulting in higher survival rates and aggravating the occurrence of pests in the next year.The heavy wind and rainstorm in a short period can reduce the number of pests in fields,especially the small insects such as mulberry thrip and red spider.High temperature can significantly increase the number of red spiders;high temperature and humidity will increase the hatching rate of lepidopteran pests,increasing the damage to the mulberry.4.The control tests showed that:(1)10%Imidacloprid and 0.2%Emamectin benzoate and their mixture all had a good control effect on the eggs of mulberrywhiteflies;10%Imidacloprid + 25%Buprofezin could control the nymphs and pupae of mulberry whiteflies,2%thuringiensis-Emamectin and 80%DDVP also performed well;10%Emamectin + 25%Buprofezin could also control the adults of mulberry whiteflies(80.75%),but other treatments showed worse control.(2)40%Propyl bromide-Octathiophos cream had a good control on young mulberry loopers after seven days of drug use.(3)For the mulberry pyralid of fourth generation,UAV showed a better control than the common sprayer.(4)The trimming of dead branches in winter could control the mulberry weevils,and helped to breed the silkworms safely.5.According to the climatic characteristics of Rugao and the occurrence of mulberry pests,this study summarized the relevant annual control methods.Strengthen the agricultural control in early spring,suppress the population of major pests and reduce their occurrence in autumn,for example,eliminate the overwintering lepidopteran larvae,cut the injured branches,clean away the weeds,dredge the canal,etc;after the branches of mulberry were cut in June,focus the management on the mulberry weevils,mulberry pyralid,mulberry looper,Spodoptera litura,mulberry thrip and red spiders.In addition,the integrated control methods of mulberry whiteflies are proposed.Finally,more publicity and training should be conducted to guide and improve the farmers' skills of pest control.