Experimental simulation of transmission of an obligate aphid pathogen with aphid flight dispersal.

The wide dispersal of Entomophthorales-caused mycoses that usually regulate aphid populations is most likely to be associated with the flight of infected alates. This hypothesis was examined via simulated flight and postflight colonization of Myzus periscae alates exposed to spore showers of Pandora neoaphidis, a common obligate aphid pathogen prevalent world wide. A total number of 407 alates were showered in different batches, then individually flown in a computer-monitoring flight mill system and reared on cabbage leaves for 14-day free reproduction and contagious infection within progeny colonies at 20-23 degrees C. On average, 80.6% of them flew 2.6 km in 1-5 h, survived 3.2 days, produced 5.3 nymphs, and transmitted their infection to progeny successfully. However, 9.8% of the flown alates left no progeny although they survived at least 1 day prior to mycosis while the rest were not mycosed, producing significantly more nymphs during the first week. The flight distances of the infected (0.01-10.2 km) or uninfected alates (0.1-8.3 km) were exponentially correlated to the flight time (r( 2) >or= 0.98). When grouped by the flight ranges of <1.0, 1.0-3.0, 3.0-5.0 and >5.0 km, the number of live aphids and the proportion of mycosed individuals per progeny colony over colonization days fit well to a complex logistic model (r( 2) = 0.984) and modified Gompertz model (r( 2) = 0.978) respectively. Both models included flight distance, postflight survival time, premycosis fecundity and primary infection rate as independent variables to affect the developmental rates. The results highlight the significant role of infected alates in the wide dispersal of P. neoaphidis-caused mycoses among aphids.