Preliminary Studies On Interspecific Competition Between Liriomyza Sativae, L. Trifolii And L. Huidobrensis

Liriomyza sativae Blanchard, L. huidobrensis (Blanchard), L. trifolii (Burgess) are three invasive insect pests of vegetable crops and ornamental plants in china and elsewhere in the word which have caused tremendous economical losses. Due to having these characteristics such as high fertility, short development cycle, wide host range, resistance to pesticides, easy breakout, etc., they are very difficult to control. Since 1970s, the three species of Liriomyza constantly spread to other countries all over the world. In recent years, interspecific competition and displacements occur occasionally among the three Liriomyza species. Here, the research progresses on interspecific competition among the three Liriomyza species were summarized. The possible mechanism for those competition phenomenon are also discussed. Impacts of temperature, volatiles and reproductive interference on interspecific competion among the three leafminer species were examined. Population dynamics of the three leafminer species were surveyed. These information and our results will be helpful to provide new strategy for controlling leafminers and provided knowledge on leafeminers pest status evolution.The results are summarized as follows:Research progresses on interspecific competition among these three Liriomyza species were summarized. The possible mechanism for those competition phenomenon are also discussed. There are many reasons which can cause displacements between different leafminers, such as interspecific hybridization, reproductive interference, natural enemy, niches, host plants, susceptivity to pesticides, appearance of new dangerous biological type.Impacts of temperature on interspecific competion between L. sativae and L. huidobrensis were determined. It was found that there was significant difference on the number of F1 adults between L. sativae (0.4±0.3) and L. huidobrensis (2.5±0.7) in 18℃; in 25℃, the number of L. sativae adults (7.6±3.0) were more than that of L. huidobrensis adults (4.3±2.0) in F1 progeny, but no significant difference; in 30℃,there were only L. sativae adults (18.0±2.9) in F1 progeny.Influences of high temperature on interspecific competion between L. sativae and L. trifolii were determined. It indicated that L. trifolii had a stronger capability against high temperature than L. sativae. There was no significant difference on the number of F1 adults between L. sativae (5.2±1.9) and L. trifolii (6.2±1.2) in 28℃, but there was significant difference on the number of F1 adults between L. sativae (0.8±0.3) and L. trifolii (4.5±1.1) in 35℃.Responses of L. sativae, L. huidobrensis and L. trifolii female leafminers to odours of ovipositing leaves, lavae leaves and attractiveness of female leafminers to male leafminers were tested with a Y-tube olfactometer. It was found that ovipositing leaves and lavae leaves had some repellent function to female leafminers, and the order from high to low was L. sativae lavae leaves≥L. huidobrensis lavae leaves>healthy leaves, L. sativae ovipositing leaves>L. huidobrensis ovipositing leaves>healthy leaves; L. trifolii lavae leaves≥L. sativae lavae leaves>healthy leaves, L. trifolii ovipositing leaves≥L. sativae ovipositing leaves>healthy leaves. The attractiveness on female leafminers to male leafminers of L. huidobrensis was significantly higher than that of L. sativae, and there was some attractiveness on female leafminers to male leafminers of L. sativae and L. trifolii, but no significant difference.Reproductive interference between L. sativae and L. trifolii was examined. It was found that there was reproductive interference between L. sativae and L. trifolii. The number of L. sativae F1offsprings descended when L. trifolii male adults were put into the cages of L. sativae, and more L. trifolii male adults, fewer L. sativae F1offsprings. On the contrary, it was samilar that L. sativae male adults were put into the cages of L. trifolii. under the same interference condition, F1 progeny ralative percentage of L. sativae was significantly less than that of L. trifolii. In reproductive interference, only the number of F1 progeny was interfered, and there were no significant differences on pupal rates, emergence rates and sex ratios.The population dynamics of L. trifolii was surveyed from 2005 to 2011. It was found that South China and Jiangsu, Zhejiang were its distribution areas some of where it caused serious damages. L. trifolii has become the dominant population in Hainan Province.