Evaluation of a Method to Quantify Glassy-Winged Sharpshooter (Hemiptera: Cicadellidae) Egg Maturation During a Feeding Assay

A method to improve an assay relating adult feeding to egg maturation by the glassy-winged sharpshooter (Hemiptera: Cicadellidae) was evaluated. The assay consisted on confining females to cowpea stems and quantifying feeding and egg maturation. Feeding was quantified by measuring excreta production. The number of eggs matured during the assay was estimated by taking the difference between female egg load (number of mature eggs carried by a female) at end of the assay (determined by dissection) and mean egg load of a subset of females dissected at start of the assay. Estimates of the number of mature eggs produced by females using the aforementioned approach improve as variability in egg loads of females entering the assay declines. As egg loads of females are variable, a pretreatment designed to reduce variance in egg loads of females entering the assay was evaluated. To accomplish this, females were divided into two groups. The control group was placed directly into the assay. The pretreatment group was given an oviposition period on sorghum before the assay. An oviposition period on sorghum was expected to reduce variance in egg load among females, as previous research found that sorghum was suitable for oviposition but provided poor nutrition for egg maturation. Dissection of a subset of females from each group before the assay determined that the mean and variance in egg load of females receiving the pretreatment was significantly reduced compared with females in the control group. Analysis of results from the feeding assay found that there was a significant relationship between feeding and egg maturation for females receiving the pretreatment, but not for females in the control group. Thus, reducing the mean and variance in egg load of females entering feeding assays resulted in detection of a significant positive relationship between feeding and egg maturation that otherwise would not have been observed.