ANNUAL RYEGRASS TOXICITY - PARASITISM OF LOLIUM RIGIDUM BY A SEED-GALL FORMING NEMATODE (ANGUINA SP)

Infection of annual ryegrass (Lolium rigidum) by Anguina sp. resulted in replacement of seeds by bottle‐shaped galls, each containing several hundred quiescent, second‐stage larvae. The biology of the nematodes, including the emergence of larvae from galls, survival in soil, and movement into and development within the host plant, has been examined. Larvae were not able to leave the galls during the dry summer, but emerged within soil 2–6 wk after normal autumn rains and following partial decay of the gall rind. Emergence took place over several months, and not all larvae emerged in any one year; they were able to survive over summer in soil both within and outside the galls. Under suitable moisture conditions, host plants were infested by larvae which climbed up the outer surfaces, became lodged within leaf sheaths, and then gradually moved towards the centre of the plant. Larvae which reached the central or axillary meristems prior to flowering were carried up with the elongating inflorescence, and attacked developing floret primordia. The nematodes developed rapidly to the adult stage, and eggs were being laid within galls by the time the inflorescence had emerged. Second‐stage larvae hatched quickly and were the only live stage remaining after the ryegrass had died. Copyright © 1979, Wiley Blackwell. All rights reserved