Study On Sex Pheromone And Host Selection Mechanism Of Apriona Germari Hope

The long horn beetle, Apriona germari Hope (Coleoptera:Cerambycidae), is one ofthe major stem borers of forests in China, which distributes widly and hascaused serious damages. The larvae destroy Poplar spp., led into danger of dead or windbreak, and caused serious impact on the forestry economy. The larvae of A. germari minein poplar stems, while the adults feed and mate in the Moraceae trees. Efficient and simplecontrol methods have not been available at present for the beetles’ control, which is stillextremely difficult in production. We studied the function of semiochemicalsand mechanism of A. germari host selection, in order to provide theoretical basis forscientifically and effectual control of A. germari, and lay the foundation ofenvironment-friendly control methods of A. germari.The chemical analysis and biological activity of body extraction in A. germari werecarried out, the results show that the semiochemicals did exist in the male and female bodysurface, and caused courtship and mating behavior of the adults, but it only worked whenliving beetles contacted each other in short distance.The GC-MS test results indicated thatthe main ingredients of semiochemicals were alkanes and alkenes containing more than10carbons, the most abundant in the ingredients was (Z)-9-Tricosene, followed byheptacosane, nonacosane and nonadecene, and some aldehyde and ester. The results ofY-tube olfactory bioassaays and contact bioassays suggested that docosene, heptacosaneand nonacosane were contact sex pheromone of the beetle females.The activity rhythms of A. germari adults showed that the peak of their matingbehaviors occurred at7:00~9:00pm and8:00am or so. The behavioral responses todifferent supplementary nutrition materials were tested under selective and nonselectiveconditions. The results revealed that the feeding area on Broussonetia papyrifera was themaximum by A. germari under selective conditions, the total oviposition for single femalewas the highest on poplars, and no significant difference was showed on the hatching rateof eggs among different supplementary nutrition materials. However, the feeding area onmulberry was the most under non-selective conditions, but eggs producted on B. papyriferareached the highest, and those on mulberries and poplars was secondary, while the feedingand oviposition on Sapium sebiferum and Melia azedarach were rare. There was noobvious difference at the egg hatching rates among B. papyrifera, mulberries and poplars.The longevity of A. germari adults feeding on mulberries and B. papyrifera was thelongest.The host selectve behavior test in A. germari adults were performed when thesensory organs interfered or plant morphology changed, the results showed that healthyadult selected host plant exactly and quikly. The beetles which were treated inantennae, maxillary palps and labial palpus could still find their host plants. Those results reflected that the beetle adults depended on olfactory senses rarely, their compound eyeshad an assisted role in host plant recognition. The adult recognized host plant after biting,which meaned that the gustatory responses played a dominant role in the host selection ofA. germariThe major nutrition components and secondary metabolites of host and non-hostplants of A. germari were measured. The results showed that water content was high inxylem of poplar stems, which reachs to40.53%, but the main nutrition of reduction sugar,total soluble sugar and soluble protein were less, the total soluble sugar and soluble proteinreached301.99μg/mg and4.07μg/mg respectively. Because of the alternate host habit of A.germari, the adults feed on the Moraceae plant for nutritional supplement, and lay theireggs within in poplar and other plants. Therefore, one or two-years-old of B. papyriferawith high nutrient and low secondary metabolites was the favorite host plants for A.germari adults.The results in this study showed that A. germari cannot produce long-range olfactorybehavior on host plants and the insect body extracts, it hard to take effect in integratedmanagement of A. germari by the attractant and other conventional chemical ecologicalmeasures. Above all, we should to plan or change the plant variety in the poplar plantationat the view of plants in the future, such as the removal of Moraceae, and grown of non-hostplants, to inhibit the formation and expansion of A. germari population. In addition, thebreeding of resistant species was also an important method to prevent A. germari.