Feeding Response Of Lepidopteral Larvae To Several Tastants And Repellence Of Non-hosts Intercropped In Brassica Oleracea Field

the author tested the effects of orthogonal combinations of six basic tastants on feeding amounts of Pieris rapae and Helicoverpa armegira larvae using leaf disk bioassay, then analyzed the effects of aroma intercrops and spaces on vegetable aphids population and P. rapae eggs deposited on Brassica oleracea plants. The main results are summarized as follows.(1)Feeding choice response of Lepidopteral larvae to basic tastant combinationsP. rapae larvae: whether under choice condition or under non-choice condition, C.annuum extract showed strongest effect on the feeding amount of P. rapae larvae, followed by Z. bungeanum extract and sucros saturated solution. The anti-feeding percentage and the dosages of Capsicum annuum extracts and Z. bungeanum extracts showed parabolic-shaped relationship.H. armegira larvae: NaCl and Z. bungeanum extracts synergistically showed the strongest anti-feeding effect. The feeding amounts of the larvae had significant relations to the dosages of Z. bungeanum extract and NaCl solution under choice and non-choice conditions, respectively.The comparison indicated that the mode of feeding deterrent of H. armegira larvae was"salty plus spicy", while that of P. rapae larvae is"sweet plus hot plus spicy". Meanwhile, the response curve of P. rapae larvae to tastants exhibited parabolic-shaped relationship, while that of H. armegira larvae exhibited linear shape, suggesting that the gustatory receptors of the formmer was easier to be passivated.Moreover, the anti-feeding percentages of many tastant combinations used in our study to the larvae of H. armegira and P. rapae reached up to 100%, being higher than plant-derived products in traditional researches, suggesting that the screening of anti-feeding substances from human basic tastants was available.(2)Repellent effect of intercrop with non-host plants of main pest in B. oleracea field.The author investigated the eggs deposited on B. oleracea plants intercropped with five non-host plant species. The results showed that the eggs deposited on B. oleracea plants intercropped with F.l vulgare was least; eggs deposited on B. oleracea plants at different distances ranging at 0.5~1.5 m from the intercrops showed extremly significant difference, and the eggs deposited on the B. oleracea plants nearer from the intercrops were less.The author further investigated aphid number distributed on B. oleracea plants intercropped with eight non-host plant species. The results showed that aphids on B. oleracea plants intercropped with C. sativum were the least, and aphid numbers on B. oleracea plants at different distances (ranging from 0.5~1.5 m) from the intercrops had no significant difference.