ALFALFA BLOTCH LEAFMINER, AGROMYZA FRONTELLA (DIPTERA: AGROMYZIDAE), EFFECTS ON ALFALFA IN VERMONT

Abstract

Seven years of field evaluation has shown the alfalfa blotch leafminer, Agromyza frontella (Rondani), to be of minor economic importance in Vermont. Although response to certain insecticidal treatments resulted in highly significant reduction in leaf mining at time of cut, no other differences were shown. Analyses of fiber content as measured by lignin, cell wall constituents, acid detergent fiber, quality as measured by % protein and % digestibility, and yields in dry weight (kg/ha) showed no significant differences. Comparison of leaflet dehiscence from field-cured and baled samples failed to indicate differences between blotched and healthy alfalfa.Two imported parasite species, Chrysocharis punctifacies Delucchi and Dacnusa dryas (Nixon), are established within the state; we predict that these parasites combined with native species will effect a decline in alfalfa blotch leafminer levels below any conceivable economic threshold.