Populations of Ipomoea hederacea var. integriuscula in Field Margins Are Maintained by Seed Production of Individuals from a Specific cohort

Abstract

Entireleaf morning glory (Ipomoea hederacea Jacq. var. integriuscula A. Gray) is a difficult-to-control weed that causes severe yield loss in soybean (Glycine max L.). It invades fields from the field margins and contributes to maintenance of the populations in the fields. This study aimed to determine the optimal period to control the populations in field margins effectively. We identified the naturally emerging plants in field margins and adjacent fields. We recorded the number of invading vines and the timing of flowering and fruiting of several cohorts (each cohort comprised a group of individuals that emerged within a certain time frame). The main seed-producing cohort on the field margins was a cohort that emerged from early August to mid-September and flowered and fruited after mid-September. The weed formed seed banks in the field margins, maintained by repeated depletion and accumulation during the emergence and seed production stages. The weed control rate by weed management practices was higher in field margins (100%) than in the fields (76%). In conclusion, the entireleaf morning glory populations were maintained by specific cohorts in field margins and weed management practices from early August to mid-September can effectively reduce its population size in the field margins.