Seasonal Phoresy As An Overwintering Strategy Of Aceria Pallida Carried By Bactericera Gobica

The gall mite Aceria pallida Keifer and psyllid Bactericera gobica Loginova are two major pests of wolfberry Lycium barbarum L., which is a deciduous woody perennial plant whose fruits, known as Goji or wolfberry, are used in traditional Chinese medicine. Because of the tiny size of A. pallida and they are hidden within shelters between plant tissues and are less vulnerable to pesticide, it is still the key point and hard job for A. pallida control. The majority of eriophyoid mites are tend to overwinter on their host plant, and they are most frequently found on buds and in bark crevices. While preliminary observations found no A. pallida in these common hibernation sites on the host plant, but many mite galls were found in L. barbarum spring buds and were closely related to the eggs laid by B. gobica. We hypothesized that these psyllids likely contribute to the outbreak and prevalence of the mites because no galls occurred if the buds were isolated from adult psyllids in early spring. Therefore, we investigated this mite phoresis on psyllids, focusing on the attachment period in the late fall and the detachment period in the early spring, and determine an effective strategy to manage this mite, and to provide a theoretical basis for Integrated Pest Management (IPM).1, During the growing season, the active mode of dispersal of A. pallida is by walking within one plant, always spread from base to top of branch along with the growth of wolfberry. The major dispersal mode of A. pallida between plants was by winds. There were many arthropod species lived within the galls, include Cirrospilus eniophyesi, Psilothrips indicus, Phthorimaea sp. etc., and their activities may also contribute to the dispersal of A. pallida.2, We first found and proved that the seasonal phoresy of a wholly phytophagous mite A. pallida is a typical obligate phoresy. The primary hibernation site of A. pallida is not on the host plant but as a phoretic on B. gobica. The mites accompanied the psyllid B. gobica to its winter hibernation sites, thus successfully escaping unfavourable winter conditions, and returned to reach the buds of their host plant early the following spring. This overwintering strategy that has contributed to the outbreak of A. pallida in early spring, which are hard to control.3, The phoresy of A. pallida was also artificially induced under conditions similar to the attachment period in late autumn, with low and alternating day-night temperatures and short photoperiod. And the phoretic mite A. pallida can easily dismount from its carrier psyllid to the host plant under suitable conditions. The mite A. pallida have no significantly preference of the adult B. gobica and not sensitive to the light condition during the attachment period. The suitable site for attachment and detachment of mites were found out mainly by their continuous exploring behaviour. The humidity was the key factor influencing the survival of the B. gobica and A. pallida under low-temperatures, and has become the prerequisite for phoresy of A. pallida.4, The gall mite A. pallida can affect the psyllid B. gobica during growing season by forming galls. The development of psyllid nymphs on galled leaves was much slower than on clean plants. However, there was no significant effect of galled plants on the fertility, oviposition preference and offspring survival of B. gobica. The decreased honeydew secretion of B. gobica nymphs which feed on galled leaf can decrease probability of being detected by parasitic wasps. There was a significant effect of galls on herbivory, with flea beetle consuming more ungalled leaves than galled leaves. Indicating that the galls will reduce the competition from their competitors.5, Based on the above finding, the management of phoretic A. pallida was studied. We found that the phoretic mites can dismount inside the wolfberry buds within 3 days after bud opening, and approximately 74% of the mites dismounted within one week. The key to managing A. pallida was to control the phoretic host psyllid before the gall mite detached. And these mites can be managed by isolating the psyllids from spring buds before bud break.In this study, we first reported the seasonal phoresy relationship between the two major pests of L. barbarum, A. pallida and B. gobica, which the primary hibernation site of A. pallida is not on the host plant but as a phoretic on B. gobica. And the dispersal mode of A. pallida during the growing season were also studied. This work provide useful information for the management of the major pests of L. barbarum, and has important scientific significance and application value for the green production of wolfberry.