Variation in Fecundity and Sexual Morph Production among Insecticide-Resistant Clones of the Aphid Schizaphis graminum (Homoptera: Aphididae)

Abstract

The reproductive potential of insecticide-resistant greenbugs, Schizaphis graminum (Rondani), was investigated. Several clones each of the 3 esterase phenotypes associated with insecticide resistance and designated susceptible (S), pattern 1 (R1), and pattern 2 (R2) collected from Colorado, Kansas, and Texas were induced into the sexual phase (when possible) and inbred or outcrossed to S clones to identify clones which may be used in inheritance studies. Most of the R2 clones could not be induced into the sexual cycle; only oviparae were produced from clones that entered the sexual phase. Seven of 10 of the S clones, 5 of 10 of the R1 clones, and 6 of 30 R2 clones tested entered the sexual cycle. Three greenbug clones, one each of S, R1, and R2, were induced into the sexual cycle and inbred or crossbred to determine their reproductive capacity. Crosses with susceptible females averaged the highest number of eggs per cross, followed by R1 females, and then by R2 females. This study further substantiates that fecundity in the greenbug is variable, and suggests that insecticide resistance may be associated with reduced fecundity in certain insecticide-resistant greenbug clones.