莲草直胸跳甲幼虫在黄瓜和豇豆上的安全性表现

The security performance of Agasicles hygrophila larvae in Cucumis sativus and Vigna unguiculata

莲草直胸跳甲(Agasicles hygrophila)为引进我国控制入侵种喜旱莲子草(Alternanthera philoxeroid es)的专食性天敌.它在主要植物上是否安全直接影响到其生防价值和生态安全.对前人已研究过的且对莲草直胸跳甲有影响的非靶标植物进一步研究,从莲草直胸跳甲的趋性、取食及非靶标植物对幼虫的寿命长短、生长发育的影响等指标筛选出黄瓜(Cucumis sativus)、豇豆(Vigna unguiculata)等植物,并采用涂抹汁液饲喂法、全汁液饲喂法和植物表皮毛数量与类型测定、植物表皮毛处理等方法来研究目标植物对莲草直胸跳甲幼虫的致死原因.结果显示:莲草直胸跳甲对豇豆、黄瓜叶片有趋性和轻微取食现象,且其幼虫在豇豆叶片上聚集性死亡,因此其幼虫对黄瓜、豇豆是安全的.莲草直胸跳甲幼虫取食豇豆、黄瓜叶片汁液48 h内存活率为100%,豇豆叶片表皮毛为钩状,且其背面表皮毛的数量最多,为139±14.11,其中幼虫在豇豆叶片背面死亡率最高,为53.33%±0.09%.2龄幼虫在豇豆叶片背面的脱离率最小,为6.67%±0.03%,去除豇豆叶片表皮毛以后,幼虫在豇豆叶片上的脱离率为100%.综上,豇豆、黄瓜叶片汁液对莲草直胸跳甲幼虫生存影响不显著,钩状表皮毛对莲草直胸跳甲幼虫有致死作用,表明非靶标植物的物理性状在引进天敌昆虫适应性上为不利因素.

Agasicles hygrophila is a special natural enemy of insect feeding exclusively on the invasive species Alternanthera philoxeroides.In respect of A.philoxeroides biocontrol,whether A.hygrophila feeding on the local vegetables directly affects the biocontrol value and ecological security.On the basis of laboratory study and previous research,we chose some non-target vegetables for A.hygrophila to study the preference,feeding,longevity,growth and development of its larvae.The results showed a slight feeding phenomena of A.hygrophila towards Vigna unguiculata and Cucumis sativus but the larvae died quickly afterwards.To find out the cause of larvae death,we applied juice of both local vegetables on A.philoxeroides leaves and fed the larvae.Then we measured the number of plant trichomes and identified the trichome types.The results showed 100% 2nd-instar larvae survival rate within 48 h of feeding on the leaf juice of cowpea and cucumber.Cowpea leave trichomes were hooked,with the maximum amount of trichomes on the abaxial surface of leaves（139 ± 14.11）;larvae feeding on cowpea leaves had the highest mortality rate（53.33 ± 0.09%）,compared with the other plants.The probability of larvae escaping from cowpea leaves was the lowest 6.67 ± 0.03%;after removing the cowpea leaf trichomes,all the larvae successfully escaped from the cowpea leaves.The results showed that the leave juice of V.unguiculata or C.sativus did not have significant effect on A.hygrophila larvae survival;it was the hook trichomes of V.unguiculata that caused the death of lavae.These results indicated that the physical properties of non-target plants had negative effects on the adaptability of introduced insects.