1.13.7
BIOLOGY OF CUCUMBER MOSAIC VIRUS IN PEPPERS IN SOUTHERN ILLINOIS, USA

CJ D'ARCY1, H HOBBS1, G KAGEZI2, DM EASTBURN1, RA WEINZIERL1, D VOEGTLIN3 and JD KINDHART2

1Department of Crop Sciences, and 2Department of Natural Resources and Environmental Sciences, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA; 3Natural History Survey, Champaign, IL 61820, USA

Background and objectives
Cucumber mosaic virus (CMV) has caused millions of dollars in yield losses of bell (sweet) peppers grown in southern Illinois during the past 5 years. CMV is known to infect a large number of plant species and to be transmitted by many species of aphids [1, 2]. The objectives of this study are to identify the important aphid vectors and to determine the local plant hosts of the virus in southern Illinois.

Materials and methods
Aphids were trapped in and around pepper fields on stationary vertical interception nets and in suction traps in 1996 and 1997. Live-trapped insects were caged on pepper seedlings for a minimum access period of 3 h to test for CMV transmission. All aphids that were recovered were identified to species. In 1996, 1296 weeds of 18 species and in 1997 2632 weeds of 40 species, from in and around pepper fields, were tested for CMV infection by double-antibody sandwich ELISA. In 1997, 941 pepper transplants also were tested by DAS-ELISA. Results were confirmed by Western blotting.

Results and conclusions
A total of 1389 and 440 aphids representing over 70 species were trapped on interception nets and subsequently recovered after transmission tests in 1996 and 1997, respectively. Only two aphids transmitted CMV to test pepper seedlings in 1996. One aphid was Therioaphis trifolii; the second was not recovered. A total of 412 and 234 aphids representing over 40 species were caught in suction traps in 1996 and 1997, respectively. The most common aphids trapped were Lipaphis erysimi, Rhopalosiphum padi, R. maidis and Schizaphis graminum. These four species have been reported previously to transmit CMV to peppers. Two aphid species, Carolinaia carolinensis and Myzus hemerocallis, were found for the first time in Illinois. Weeds that were positive for CMV infection in 1996 were 171101 nightshade (Solanum sp.) and 12130 groundcherry (Physalis sp.) plants. The same two species were positive for CMV in 1997 (151408 nightshade; 2/58 groundcherry). Aphis fabae subsp. solanella colonies were commonly found on nightshade. Pepper transplants were negative for CMV infection (0/941). These results implicate several potential aphid vectors of CMV in southern Illinois and indicate that the weeds probably serve as local sources of the virus.

References
1. Edwardson JR, Christie RG, 1986. Monograph 14, IFAS, University of Florida, pp. 143-214.
2. Palukaitis P, Roosinck MJ, Dietzgen RG, Francki RIB, 1992. Advances in Virus Research 41, 281-349.