VIEW ARTICLE

Ecology and Epidemiology

Survival of Verticillium albo-atrum from Alfalfa in Feces of Leaf-Chewing Insects. H. C. Huang, Plant pathologist, Agriculture Canada Research Station, Lethbridge, Alberta, Canada T1J 4B1; A. M. Harper, crop entomologist, Agriculture Canada Research Station, Lethbridge, Alberta, Canada T1J 4B1. Phytopathology 75:206-208. Accepted for publication 21 September 1984. Copyright 1985 Department of Agriculture, Government of Canada. DOI: 10.1094/Phyto-75-206.

Alfalfa leaves infected with Verticillium albo-atrum were fed to leaf-chewing insects—grasshoppers (Melanoplus sanguinipes and M. bivittatus), alfalfa weevil (Hypera postica), and woolly bear (Apantesis blakei)—to determine survival of the pathogen after passage through their digestive tracts. V. albo-atrum survived in the digestive tracts of all tested species, usually first appearing in the feces 1 day after feeding. The percentage of feces contaminated by V. albo-atrum varied among individuals within species and was related to the duration of feeding on diseased tissues. The average percentage of contaminated feces in adult M. sanguinipes was less than 14% after 1 day of feeding the insects with diseased tissue but increased to 49% after 3 days of feeding. V. albo-atrum was eliminated from the digestive tracts of grasshoppers by changing the diet to uninfected alfalfa leaves. The time required for complete removal of the pathogen appeared to be related to the level of contamination in digestive tracts, averaging 1.6 days for individuals with less than 25% of pathogen-contaminated feces and 6.1 days for those with more than 75% of contaminated feces in their digestive tracts. When grasshopper feces contaminated with V. albo-atrum were buried near roots of alfalfa seedlings, 20.8 and 13% of plants became infected and developed wilt symptoms after 6 wk in experiments 1 and 2, respectively. The role of leaf-chewing insects in the dissemination of V. albo-atrum in alfalfa and other crops is discussed.