Feeding Preference And Bionomics Of Three Species Of Armyworm On Different Host Plants

Mythimna separata(Walker),Leucania loreyi(Duponchel),Leucania roseilinea(Walker)are three species of armyworm relatives.They are all important agricultural,and can be outbreak in our country.In order to provide scientific basis for prediction and control of three species armyworm,the present experiment was conducted to investigate feeding preference and bionomics of three species armyworm to four species host plants viz.maize,rice,sugarcane and barnyard grass.The main results are as follows:1.The feeding preference of three species armyworm larvae to four species host plants was studied by leaf disc method.The results showed that each instar larvae of M.separata preferred maize most at the 24h observation time,and the rates of 1st and 2nd instar reached as high as 82%and 89%.All the instars of L.loreyi preferred to feed on maize,especially the feeding trend of young larvae was obvious than that of the elder's.All the instars of L.roseilinea showed feeding preference to rice.But there was no significant difference in the feeding preference rates of 2nd to 4th instar larvae to rice and maize.Each larvae of three species of armyworm had temporarily feeding behavior.It varied with different instars,and the preference of adult larvae was not as obvious as the earlier larvae to host plants.2.The growth periods of three species of armyworm were observed and recorded,the results showed that different host plants have different effects on the growth and development.The development stages of three species of armyworm on rice and maize were significantly shorter than those on sugarcane and barnyard grass,and adult longevity was longer,too.The average developmental period of the larvae of M.separata on maize and rice was shorter,were 20.38±0.37d and 21.75±0.41d respectively,the average of adult longevity was 11.08±0.36d to 12.78±0.42d.The average larval period of L.loreyi on maize and rice were 20.18±0.24d and 21.29±0.45d respectively,the adult longevity was also about 11.18±0.30d to 12.33±0.51 d.Larvae of L.roseilinea on rice were grew fast,then on maize,the larvae stages were 22.52±0.40d and 22.96±0.26d respectively,the average adult longevity was span 10.55±0.34d to 11.07±0.49d.It indicated that maize and rice were the more suitable host plants for the three species armyworm.3.The pupa weights of M.separata and L.loreyi were heavy on maize.It's also the most conducive to fecundity and eggs hatching rate on maize.While the pupa weights of L.roseilinea were heavy on rice.It's the most conducive to fecundity of the female adults and eggs hatching rate on rice,too.The average fecundity of M.separata on maize was up to 1183.38±154.31eggs,the hatching rate was 94.40±0.79%.A single female adult of L.loreyi laid 1019.42±95.22 eggs on average,hatching rate was 93.59±0.93%.But a single female adult of L.roseilnea on rice just laid 632.31 ±39.31 eggs on average,the hatching rate was 92.43±0.71%.The results showed that the adult fecundity was related to the feeding preference of larvae on 4 host plants.4.The population parameters of the three species of armyworm were different on different host plants.The net reproduction rate,intrinsic rate of increase and finite rate of increase on 4 host plants of M.separata and L.loreyi were as follows:maize>rice>barnyard grass>sugarcane.While the population doubling times of them were on the contrary.The population parameters of L.roseilinea were the highest on rice,then on maize.In addition to the net reproduction rate on sugarcane was higher than that on barnyard grass,the other parameters on sugarcane were the lowest.The population doubling time on rice was the shortest,sort as follows:rice<maize<barnyard grass<sugarcane.Although the parameters of three species armyworm on sugarcane were lower than that on the other hosts,the net reproductive rate still exceeded 100,and the intrinsic rate of increase also exceed 0.It meant that the population of three species of armyworm on sugarcane showing a growing trend.