Study And Application On The Factors Affecting The Oviposition Of Plutella Xylostella On Eight Cruciferous Plants

The diamondback moth(DBM)Plutella xylostella belongs to the Lepidoptera Plutella family and is distributed in 84 countries and regions in the world.DBM distributed in all parts of China,but most seriously in the middle and lower reaches of the Yangtze River.It mainly damages cruciferous plants and causes huge economic losses to vegetable production all over the world every year.DBM mainly relies on adults to spread.The selection of suitable oviposition sites on host plants by adults plays an important role in the growth and development of their offspring and population reproduction.However,how the DBM lays eggs on different host plants and the factors that affect the DBM lays eggs are not fully understood.Therefore,in this article,the oviposition behavior of DBM adult on 8cruciferous plants such as cabbage,Chinese kale,Chinese cabbage,radish,oilseed rape(Shaanyou 0913 and Ganza 1),and edible rape(Siyueman and Chaojihuojiqing)was conducted,and the main factors affecting the DBM to lay eggs and the reason why the larvae damage increased the eggs laid on the Chinese kale were investigated.Finally we designed a dead-end trap system for the DBM.The main results achieved are as follows:1.Oviposition selectivity of DBM adults.Studies have shown that the cotyledons of cruciferous plants are the place where DBM adults prefer to lay eggs.The egg density on the cotyledons of cabbage,Chinese kale,Chinese cabbage,Shaanyou 0913,Ganza 1,Siyueman and Chaojihuojiqing was exceeded 5 grains/cm2.The egg density of the DBM on the cotyledons of cabbage and Chinese kale was 13 and 12.9 times than that on true leaves,respectively.When 8 kinds of leaves were selected at the same time,the cabbage,Chinese kale and Shaanyou 0913 attracted the least eggs,radish,Chinese cabbage and Siyueman had the highest amount of eggs.Larvae pre-infested can significantly increased the number of eggs laid on cabbage,Chinese kale and Shaanyou 0913,however,the other five plants were not affected.2.The effect of glucosinolate content of host plants on the oviposition of DBM.Studies have shown that the oviposition preference of DBM is not significantly related to the glucosinolate content in the leaves.DBM lays the least eggs on the cabbage and Shaanyou0913 leaves with the highest total glucosinolate content.There are significant differences in the total glucosinolate content in the true leaves and cotyledons of Ganza1,Shaanyou 0913 and Chaojihuojiqing,but the difference in the egg density of DBM between true leaves and cotyledons on this three seedlings was not significant;the total glucosinolates content between true leaf and cotyledon of Chinese cabbage was not significantly different,but the egg density on true leaf was significantly higher than that of cotyledon;the total glucosinolate content in true leaf of Chinese kale was significantly higher than that in the cotyledon,but the egg density is significantly lower than that of cotyledons.The density of DBM eggs on the leaves of Siyueman,radish and cabbage was consistent with the total concentration of glucosinolates.3.The role of host plant surface physical properties in oviposition selection of DBM adults.The results showed that there was a negative correlation between wax content and oviposition preference of DBM adults on leaf surface,and a positive correlation between leaf surface trichome density and oviposition preference of DBM adults.The oviposition preference of DBM on less waxy plants such as cabbage,radish,Siyueman and Chaojihuojiqing was positively correlated with the total content of glucosinolates.Wax powder on plant surface hindered DBM adults to lay eggs,DBM rarely laid eggs on the leaves with thick wax,but on the wax removed leaves,the number of eggs increased significantly.4.Adaptation strategies of DBM to wax plants.In the long-term evolution process,DBM could overcome the obstruction of the leaf wax through the synergistic effect of adults and larvae: DBM adults first lay eggs on the cotyledon of Chinese kale,which was not suitable for larvae to feed,but the hatched larvae can climb on true leaves to feed and form a silk "ladders" when crawing and a silk "net" before feeding which changed the surface structure of the leaves.These structures significantly increased the number of eggs laid by the DBM adult on the true leaves of Chinese kale.5.A dead-end trapping system for DBM was designed.The adults of DBM laid more eggs on faba bean sprayed with Chinese kale extract than on Chinese kale itself.The first instar larvae of DBM could not survive on faba bean.The results in the greenhouse showed that faba beans sprayed with Chinese kale extract were most attractive to adults of DBM when placed at a distance of 3 meters from Chinese kale.Moreover,this attraction effect of faba beans on P.xylostella for oviposition lasted for up to 15 days.The main crops and trapping plants in the trapping system are not limited to cabbage and faba beans.Other thick waxy cruciferous crops and wax-free non-cruciferous plants all have the potential to be included in the system.In summary,this article analyzes the main factors affecting the DBM's oviposition by studying the DBM's oviposition behavior on 8 cruciferous plants,and we clarifies for the first time that the DBM larvae help their adults overcome the host plant wax?s hindrance by spinning silk,so as to complete population reproduction.At the same time,a new dead-end trap system of DBM was established,which provides a new proof of concept of using a non-cruciferous trap plant for P.xylostella management.