Effect of endophyte-infected tall fescue on the japanese beetle and other selected soil insects

Field and laboratory studies were conducted to establish if soil insects are adversely effected by Acremonium coenophialum-infected (E+) or non--infected plants (E-). Studies with Japanese beetle (JB) (Popillia japonica) indicate that toxic factors are present in roots of E+ plants. Survival of first instar JB was significantly lower in the presence of E+ roots or peat soil which had been exposed to E+ roots than in the presence of E- roots or soil which had been exposed to E- roots. Results indicate that toxins in soil have a limited activity period and might be loline alkaloids (pyrrolizidine), which are volatile and known to occur in roots of E+ plants or other unknown toxins. JB eggs appeared to be unaffected by E+ plants. Field studies with natural populations of JB or artificial infestations of eggs into field plants proved difficult and did not produce conclusive results. Potted plants infested with JB eggs and placed into the field had significantly more third instar larvae surviving in 80% E- plantings than 80% or 100% E+ plantings after a 3-month period. Preliminary evidence indicates that E+ plants may be resistant to JB larvae due to deterrence.

Other insects studied for effects of E+ plants were Cyclocephala sp., Conoderus sp., and sminthurid springtails. Field populations of Cycloceohala did not indicate significant differences in abundance between E+ or E-, but field collected larvae placed in potted fescue plants for 1 month demonstrated significant reductions in E+ plants. Conoderus larvae were not significantly more abundant in E+ or E- field plants. Pitfall collections of Collembola indicate relative abundance of Sminthuridae were reduced in E+ field plots. Bourletiella (Deuterosminthurus) lippsoni Snider and Sminthurides (Sphaeridia) serratus Folsom and Mills were the two predominant species and both occurred in greater abundance in E- fescue plots than E+ plots.

Findings of this study indicate that soil insects are affected by the presence of A. coenophialum in fescue plants and that these effects occur in the root regions of the plant.