|RANGASAMY, MURUGESAN - Dow Agrosciences|
|MCAUSLANE, HEATHER - University Of Florida|
|CHERRY, RONALD - University Of Florida|
Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/3/2014
Publication Date: 4/1/2015
Citation: Rangasamy, M., Mcauslane, H.J., Backus, E.A., Cherry, R.H. 2015. Differential probing behavior of Blissus insularis (Hemiptera: Blissidae) on resistant and susceptible St. Augustinegrasses. Journal of Economic Entomology. 108(2):780-788.
Interpretive Summary: St. Augustinegrass is the most common turfgrass in Florida and other areas of the southern United States. The 400,000 hectares of St. Augustinegrass in Florida alone are valued at $199 million annually. The annual cost of controlling the most important pest of St. Augustinegrass, the southern chinch bug, was estimated at $5 million in 1983 in Florida alone, and is undoubtedly much more costly today. Recently, the economic importance of this insect has increased because it has developed resistance to several commonly-used insecticides. A more environmentally friendly method than insecticides to control chinch bug infestations is host plant resistance, but improvements in resistance are still needed before new varieties of St. Augustinegrass can be commercialized. This study used electrical penetration graph (EPG) monitoring of insect feeding to identity mechanisms of resistance to chinch bug feeding in two resistant varieties (FX-10 and NUF-76) of St. Augustinegrass compared with two susceptible varieties (Floratam and Palmetto). Overall, chinch bugs fed significantly less on resistant FX-10 and NUF-76 than on susceptible Floratam and Palmetto. During feeding in resistant varieties, chinch bugs had difficulty finding and accepting a phloem cell for sucking sap. In addition, the duration of phloem-sap sucking was significantly reduced on FX-10 compared to that in susceptible varieties. Thus, chinch bug resistance factors were found in non-phloem tissues in both NUF-76 and FX-10, as well as in phloem in FX-10. Knowledge of the types and locations of resistance factors will help breeders further improve resistant varieties of St. Augustinegrass for eventual commercialization.
Technical Abstract: Southern chinch bug, Blissus insularis Barber, is a severe pest of St. Augustinegrass throughout the southern United States. Host plant resistance is an environmentally friendly method to manage chinch bug infestations and is increasingly important as the southern chinch bug develops resistance to commonly-used insecticides. In this study, in an effort to understand resistance mechanisms in two varieties of St. Augustinegrass (FX-10 and NUF-76), electrical penetration graph (EPG) monitoring was used to quantify stylet probing behaviors of chinch bugs on two resistant and two susceptible St. Augustinegrass varieties. Overall, chinch bugs spent less time probing on resistant FX-10 and NUF-76 than on susceptible Floratam and Palmetto, and individual probes were shorter in average duration but more numerous in resistant varieties than in susceptible varieties. During probing, chinch bugs spent longer in pathway-associated stylet activities (i.e., penetration through epidermal and mesophyll tissue) in the resistant varieties than in the susceptible varieties, likely indicating difficulty in finding and accessing an ingestion site. As a consequence, chinch bugs spent proportionately much less time engaged in xylem ingestion in both resistant varieties than in susceptible varieties, but only in FX-10 were phloem-associated activities significantly reduced compared to those in susceptible varieties. Thus, there is evidence for non-phloem-associated chinch-bug resistance factors in both NUF-76 and FX-10, and phloem-associated factors in FX-10.