Susceptibility of Italian ryegrasses (Lolium multiflorumLam.) to Argentine stem weevil (Listronotus bonariensis(Kuschel)) feeding and oviposition

Abstract

The susceptibility of Italian ryegrasses (Lolium multiflorum Lam.) to Argentine stem weevil (Listronotus bonariensis (Kuschel)) was investigated in laboratory feeding and oviposition experiments, and in a field trial. Some Italian ryegrasses (for example, ‘Concord’, ‘Corvette’, ‘Progrow’) are infected with an Acremonium-like endophytic fungus. The presence of Acremonium-like endophyte did not deter or reduce adult Argentine stem weevil feeding or oviposition. The introduction of Acremoniun lolii Latch, Christensen&Samuels endophyte isolated from perennial ryegrass (L. perenne L.) into L. multiflorum conferred resistance to L. multiflorum from Argentine stem weevil feeding. Lolitrem B (a tremorgenic mycotoxin) concentrations ranged from 0.2 to 4.50 μμ/g and from 0.01 to 0.09 μμ/g dry weight of grass in A. lolii-infected and Acremonium-like infected L. multiflorum, respectively. This indicates that the level of insect and animal feeding deterrents and toxins are dependent on the species of endophytic fungus in the plant. The Italian ryegrasses produced 0–1298 kg more dry matter (DM) than ‘Ellett’ during the period 3 June–15 December 1986. Largest Argentine stem weevil populations were recorded on ‘Grasslands Moata’. There were no significant differences in the density of Argentine stem weevil between the Italian ryegrass cultivars.