Preferences And Responses Of The Diamondback Moth To Brassica Oleracea And Orychophragmus Violaceus At Different Temperatures

Plutella xylostella is a oligophagous pest that feeds on cruciferous plants.The distribution of diamondback moth is closely related to the distribution of cruciferous crops and wild cruciferous plants.In the absence of crops,wild cruciferous plants,as an alternative host,provide a natural shelter for the diamondback moth,which plays a significant role in maintaining the survival and reproduction of diamondback moth.Brassica oleracea is an important cruciferous crop,and Orychophragmus violaceus is a common cruciferous wild plant.In this study,B.oleracea and O.violaceus were used as host plants of diamondback moth to test the oviposition preference,feeding preference,growth and development and digestive enzymes activity under different temperatures.The main findings are as follows:In this experiment,under the conditions of 16℃,23℃ and 30℃,three treatments were set: B.oleracea + O.violaceus,B.oleracea + B.oleracea and O.violaceus + O.violaceus to test the oviposition preference of DBM.The results showed that in B.oleracea +O.violaceus treatments,under each temperature DBM were prefer to lay on O.violaceus than B.oleracea.In B.oleracea + B.oleracea and O.violaceus + O.violaceus treatments,under 16℃ the fecundity of DBM was significantly lower than that under 23℃ and 30℃.Under the conditions of 16℃,23℃ and 30℃,the feeding preference of DBM larva were tested using leaf discs assay.The results showed that the host plants had a significant effect on the feeding preference of the DBM larva.The larva in each instar showed a significant preference to O.violaceus.Temperature had no effect on the feeding preference of the DBM larva.The two-sex life table of DBM feeding on B.oleracea and O.violaceus at different temperatures were built.The results showed that The growth and development of DBM were better at 23℃ than at other temperatures.The growth and development of DBM on B.oleracea were better than that on O.violaceus.In this experiment,under 16℃,23℃ and 30℃,the activity of protease,amylase and lipase in the fourth instar DBM larva that feeding on B.oleracea and O.violaceus were tested.The results showed that under 16℃,there was a significant difference in protease activity between the DBM feeding on B.oleracea and O.violaceus.Under different temperature,the protease and lipase activity of DBM feeding on O.violaceus was significantly different.The temperature and host plants had no obvious effects on the amylase activity of DBM both feeding on B.oleracea and O.violaceus.Our results showed that temperature has an effect on the oviposition preference,feeding preference,growth and development of DBM.The DBM adult was prefer to lay on O.violaceus,and larva was prefer to feed on O.violaceus.However,the development of DBM on O.violaceus was inferior than that on B.oleracea.Temperature also has an effect on the digestive enzymes activity.This indicates that O.violaceus is a potential trap plant around B.oleracea field to reduce the damage of DBM.