The Influence Of Feeding By Adults Of Pseudorobitis Gibbus Redtenb Acher On Growth And Development Of Lagerstroemia Indica L.

The Pseudorobitis gibbus Redtenbacher (Coleoptera:Apionidae) is a new pest of Lagerstroemia indica L, the study in our country is mainly on biological characteristics, space pattern, prediction and forecast of population. Through indoor and outdoor test and observation, this study is conducted to explore adults of Pseudorobitis gibbus Redtenbacher (Coleoptera:Apionidae) infest different part and time of Lagerstroemia indica L such as shoots or flowers and the influence on growth and development of it. We analysis the tropism of crape myrtle to different colors preliminarily. The results are as follows:(1) Through outdoor investigation we found that adults of Pseudorobitis gibbus Redtenbacher (Coleoptera:Apionidae) can lead to different degree of infestation to the branch in different orientation, the most seriously is the upper and the eastern, the hazard ratio is95%,85%respectively; the lighter is the north and lower, the hazards rate is80%,70%respectively, the treatment is significant by the method of DPS. The adults of Pseudorobitis gibbus Redtenbacher (Coleoptera:Apionidae) damage branch of different color of Lagerstroemia indica L also differently, the most seriously is the red, the hazard ratio is86.31%; the most lightest is the white, the hazard ratio is83.12%, but the treatment is not significant by the method of DPS. The degree of damage is more and more serious with the increase of population density. When the population density is20, the hazard ratio is about95%and the population density is5, the hazard ratio is about70%. After infesting, it is not only leading to weak growth, but also delaying flowering time, decreasing the amount of flowers, reducing the ornamental value greatly.(2) Through outdoor investigation we found that the adults of Pseudorobitis gibbus Redtenbacher (Coleoptera:Apionidae) have a great influence on flowering time of Lagerstroemia indica L. The extent of damage of shoots from generation to fully flowering become more and more lighter; flower buds become light then heavy during growing, the inflection point is July13th, August18th; the level of damage of flower firstly become heavy then light. The damage of flower buds on different orientation is also different. Food consumption on flower buds in the eastern is the biggest about20%; the north is the smallest about5%, the treatment is highly significant by the method of DPS. The amount of flowers will decrease with the increasing of population density. When the population density is5per branch, the amount of flowers is about80%and the population density is40per branch, the amount of flowers is only about10%70%.(3) By the operation in the laboratory and investigation in the forest we found that:the tropism of adult of Pseudorobitis gibbus Redtenbacher (Coleoptera:Apionidae) to four kind of different colors is different. Testing with glass Petri dish and Y-type olfactometer, the result of selection is consistent:the tropism to red flower is significant, the order is red>purple>pink>white. By anglicizing, the tropism to red flower, purple flower, pink flower, white flower is highly significant (P=0.0001,0.0001,0.0002,0.0003<0.01).The result is consistent to the tropism of chemotaxis of adults. The selection is highly significant (P-0.0004,0.0001,0.0001<0.01) to red, purple, pink and white using the method of DPS, adults of Pseudorobitis gibbus Redtenbacher (Coleoptera:Apionidae) preference for red; The selection is significant (P=0.023,0.0001<0.05) to purple, pink and white, they preference for purple. The selection is significant (P=0.0001<0.01) to pink and white, they preference for pink.