The Relationship Between Sea Buckthorn Carpenter Moth,Holcocerus Hippophaecolus Occurrence And Forest Plant Diversity And Plant Volatiles

The sea buckthorn carpenter moth, Holcocerus hippophaecolus (Lepidoptera: Cossidae) is an important shrub borer that damages the sea buckthorn, Hippophae rhamnoides. The larvae have caused a major loss of the shrubs in northern China, with severe economic and ecological consequences. Large-scale cultivation of artificial sea buckthorn forest resulted in a large number outbreak of the moth. In this study, the relationships between the pest occurrence and forest plant diversity and plant volatiles were studied, and the main results are present as follows:1. By using scanning electron microscopy (SEM), the typology, morphology and distribution of sensilla on the antennae and ovipositor of H. hippophaecolus had been investegated. In total, five types of sensilla were found on the antennae, i.e., sensilla chaetica. sensilla trichodea (two subtypes), sensilla basiconica (two subtypes), sensilla coeloconica and Bohm bristles. In addition, three types of sensilla were detected on the ovipositor, i.e., sensilla chaetica, sensilla trichodea and sensilla basiconica.2. The stastics indicated that the pest prefered to either sex of sea buckthorn by pairing the larval population density in different sex sea buckthorn plants. Meanwhile, the results of the olfactometer test in laboratory indicated that the pest presented a non-significant attraction to different sex sea buckthron barches, in spite of the result showed that the pest had singnificantly attracted to the host plant. Volatiles of both male and female sea buckthorn plants were collected, and42components were eventually identified.(Z)-3-Hexen-l-ol acetate was the most aboudant content in the female plant, with a greater percentage than20%. There was no unique chemical compound was found neither in the male nor in the female plant. The content of Benzaldehyde,1-Heptanol, Naphthalene, Methyl salicylate and4-Methylnonanoic acid was more aboudant in the female than the male plant. Componets were divided into different groups based on the circadian rhythm of volatiles released during the four time periods (9:00-12:00,12:00-15:00,15:00-18:00. and18:00-21:00). Decanal, Benzothiazole,1-Octene,6-Methyl-5-hepene-2-one, Benzaldehyde, and Terpinene was constantly released at the same level during the different collection times.3-Carene. Nonanal,(Z)-3-Hexen-l-ol, and2-Ethylhexanol was released more abundantly in an earlier period than in the latter period. The emission of (Z)-3-Hexen-l-ol acetae and Naphthalene decreased from the first to third period, and then increased in the fourth period (mating peak of the moth).3. After being damaged, volatiles emission of sea buckthorn plant had been changed. The relative content of olefins. aromatics, ketones, terpenes and alkanes had the trend of increment; the relative content of aldehydes, alcohols, and esters had a downward trend, in which the relative content of alcohol and esters decreased greatly. The pests had induced a plant volatile of2-Ethylhexyl acetate.4. After being damaged, moisture content declined in all the three tested parts of sea buckthorn plant, but there was no significant differences between the healthy and damagd plant; the ash content of the plant significantly declined in the upper part and basal part; the content of potassium, manganese and zinc significantly declined in the whole plant; While, the calcium only significantly declined in the upper part. After being damaged, the total content of18types of amino acids significantly increased in the middle parts and the basal parts. Wherein, the contents of aspartic acid, lysine, histidine, proline, tryptophan and cysteine were significant increase in the middle parts. The content of proline and cysteine were significant increased at the root. Protein contents in the middle parts and the basal parts were decreased after damage. After being damaged, sea buckthorn may choose to have plant growth compensating rather than to have chemical defense.5. The occurrence of the pest in the different natural and artificial sea buckthorn forests were investgated. as well as the plant diversity and blends of plant volatile. The results indicated that the two natural sea buckthorn forests were classed to the A grade (healthy), the artificial pure sea buckthorn forest was the B grade (slight damaged), and the artificial mixed sea buckthorn and elm forest was the C grade (moderate damaged).Plant diversity of the natural pure sea buckthorn forest was higher than that of the natural mixed sea buckthorn and larch forest. and the artificial pure sea buckthorn was higher than the artificial mixed sea buckthorn and elm forest. In sea buckthorn forests, the plant diversity was correlated reciprocally with the occurrence of the pest.Varieties of plant volatiles were more aboudant in the pure sea buckthorn forest than that in the mixed forest. The most varivation content in the natural sea buckthorn forests was alcohol, and ketones followed. Besides The most varivation content in man-made sea buckthorn forests was esters, and terpenes followed.6. The female moth responsed to all21compounds, which selected from the collection of plant volatiles in the sea buckthorn forests. Methyl salicate,1-Octene,(Z)-3-Hexen-l-ol acetate, Naphthalene and alpha-Pinene elicited the singinificant resposes at the concentration of10-1μg/μL.101μg/μL,100μg/μL and10μg/μL. respectively. However. the main contents in sea buckthron forests i.e.,2-Ethylhexanol, Longifolene, Benzaldehyde and Decanal lead to a less response. The female antennae responsed to the herbiovre-induced plant volatile of2-Ethylhexyl acetate, but there were no significant differences between different concentrations.