FIELD AND LABORATORY TRANSMISSION OF WATERMELON MOSAIC VIRUS-2 AND ZUCCHINI YELLOW MOSAIC-VIRUS BY VARIOUS APHID SPECIES

Aphid transmission of watermelon mosaic virus 2 (WMV 2) and zucchini yellow mosaic virus (ZYMV) was studied in the laboratory and field to evaluate species of probable importance in the epidemiology of each virus. Relative transmission efficiencies among species were compared using alates obtained from laboratory-maintained colonies as well as from natural populations collected with an aerial net. In laboratory studies, Myzus persicae, Aphis gossypii, and Acyrthosiphon pisum transmitted WMV 2 with 18, 16, and 16% efficiencies, respectively. In similar studies, these three species transmitted ZYMV with 41, 35, and 4% efficiencies. In these laboratory studies, Acyrthosiphon kondol, Lipaphis erysiml, and Aphis spiraecola transmitted WMV 2 and ZYMV with less than 10% frequency. Field-collected M. persicae alates, whether returned to the laboratory or tested immediately in the field, transmitted ZYMV and WMV 2 at higher efficiencies than the laboratory-derived alates. Field-collected A. kondoi and A. pisum transmitted ZYMV at higher efficiencies than those evaluated in laboratory studies, but transmitted WMV 2 with lower efficiency. In a related study, a total of 18,837 alates were assayed by transmission during a 3-yr period to determine incidence of naturally occurring inoculum. Viruliferous aphids were detected only in the first season, when 44 alates representing four species transmitted virus. No alates assayed in the following two seasons transmitted virus.