THE EFFECTS OF FUSARIUM WILT AND WEED CONTROL ON SURVIVAL OF BIRDSFOOT TREFOIL

Abstract

Birdsfoot trefoil (Lotus corniculatus L.) seed production is no longer profitable for Champlain Valley farmers, partly because the plants do not grow or persist as well as they did in the past due to a Fusarium wilt disease (Fusarium oxysporum). This study was done to determine the effects of chemical and cultural weed control on birdsfoot trefoil seedlings in a Champlain-Valley clay soil containing Fusarium oxysporum. In a greenhouse experiment, 2,4-DB was applied to birdsfoot trefoil seedlings growing on pasteurized potting mix inoculated with F. oxysporum. When applied at label rate in the second trifoliate-leaf stage, and 14 days later, 2,4-DB increased seedling mortality additively with death due to F. oxysporum. When 2,4-DB was applied 7 days after the second trifoliate-leaf stage, it did not influence seedling survival. Applying 2,4-DB reduced dry weights of tops and roots of surviving seedlings. A field experiment was done on a clay soil (Glossaquic Hapludalf) being used for birdsfoot trefoil seed production and known to contain F. oxysporum. Raised beds were included as a variable to determine effects of improved root-zone drainage. Weeds were controlled by clipping or with 2,4-DB/dalapon postemergent herbicides in two birdsfoot trefoil seeding rates of 16.8 and 3.4 kg seed∙ha−1. The herbicides did not influence seedling death rate. By May of the second year plant populations within a seeding rate were the same, regardless of weed control practice and seedbed preparation.Key words: Dalapon, Fusarium oxysporum, Lotus corniculatus L., 2,4-DB