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Title: Effects of glassy-winged sharpshooter feeding, size, and lipid content on egg maturation

item Sisterson, Mark
item Wallis, Christopher
item Stenger, Drake

Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/7/2015
Publication Date: 6/5/2015
Citation: Sisterson, M.S., Wallis, C.M., Stenger, D.C. 2015. Effects of glassy-winged sharpshooter feeding, size, and lipid content on egg maturation. Journal of Economic Entomology. 108:1014-1024.

Interpretive Summary: The glassy-winged sharpshooter is an invasive insect capable of transmitting the causal agent of Pierce’s disease of grapevine. Establishment of the glassy-winged sharpshooter in California resulted in epidemics of Pierce’s disease in southern California during the late 1990’s. In response, a glassy-winged sharpshooter area-wide suppression program was initiated that relies on treating populations with insecticides. The area-wide suppression program is ongoing and is likely to continue indefinitely in absence of alternative control methods. Studies were conducted to describe effects of glassy-winged sharpshooter feeding on lipid allocation to the body versus eggs. In conjunction, effects of female size on egg production were evaluated. Low levels of feeding resulted in an initial rapid increase in lipid content of glassy-winged sharpshooter bodies. Rates of increase in body lipid content decreased with additional feeding as lipids were diverted to egg production. Accordingly, egg production was preceded by an increase in body lipid content. In general, larger females produced more eggs than smaller females. Description of key steps in glassy-winged sharpshooter egg production will aid in identifying novel targets for glassy-winged sharpshooter suppression tactics.

Technical Abstract: The glassy-winged sharpshooter (Homalodisca vitripennis) is synovigenic and must feed during the adult stage to produce eggs. While glassy-winged sharpshooter egg production is related to adult feeding, rates of egg production are variable. In this study, effects of lipid allocation to eggs and female size on glassy-winged sharpshooter egg production were investigated. Females were field collected and divided into four feeding groups. Females in the first group were dissected at start of feeding treatments. Females in the remaining three groups were held on cowpea until producing approximately 12, 25, or 50 ml of excreta. After reaching prescribed excreta thresholds, females were dissected to determine egg load, hind tibia length, and head capsule width. Mature eggs were removed from the abdomen and dry weight of eggs and bodies (head, thorax, and abdomen) were obtained. Lipid content of eggs and bodies were determined using a quantitative colormetric assay. Rates of body weight gain and body lipid gain were rapid with low levels of feeding but decelerated with additional feeding. In contrast, low levels of feeding resulted in little egg production, with rates of egg production accelerating with additional feeding. Accordingly, egg production was preceded by an increase in body dry weight and body lipid content. Across feeding treatments, larger females carried more eggs than smaller females. Investment of resources into egg production increased female weight, with eggs accounting for up to 35% of dry weight. Collectively, these results suggest a relationship between feeding, lipid accumulation, and fecundity that are mediated by female size. As nymphal diet is known to affect female size and may affect lipid reserves available to newly eclosed adults, additional research is needed to clarify the role of resources acquired during the nymphal stage on egg production.