Development of Fusarium Crown-rot in Alfalfa Stressed by Multiple Defoliations by the Yellowstriped Armyworm (Lepidoptera: Noctuidae)

Abstract

Alfalfa (Medicago sativa L.) plants (var ‘Florida 77’ and ‘Cimarron’) were injected with Fusarium oxysporum Schlecht., and stressed for four consecutive harvests by yellowstriped armyworms, Spodoptera ornithogalli (Gueneé), under greenhouse conditions. No significant interactions existed between insect defoliation and inoculation with F. oxysporum. Insect defoliation alone had significant effects on dry matter yield, stem height, and maturity, but forage quality, root weight, and root carbohydrate levels were not significantly affected. In vitro digestible dry matter (IVDDM) concentration in Cimarron was the only forage parameter affected by F. oxysporum.