DYNAMICS OF SUBECONOMIC THRESHOLD POPULATIONS OF SICKLEPOD (CASSIA-OBTUSIFOLIA) IN A PEANUT-COTTON-CORN ROTATION

Studies were conducted from 1987 to 1990 to measure the dynamics of si cklepod established at subeconomic threshold populations in a peanut-c otton-com cropping system. The experimental site had no native populat ions of sicklepod prior to initiation of the study. Main plots were cr ops in the rotation sequence plus continuous summer fallow (no crop). Subplots were: sicklepod established in the initial year of the study, sicklepod established every year of the study, and no sicklepod. Sick lepod was established at subeconomic threshold densities to simulate w eed survival and seed production in fields where economic thresholds w ere the basis for weed management decisions. Sicklepod growing alone i n fallow plots produced more seed per plant, resulting in significantl y more seedlings throughout the study than sicklepod growing with crop s. Sicklepod growing in corn produced the fewest seed per plant. Seed produced from subeconomic threshold densities established only in the first year caused 7-, 21-, and 20-fold increases in sicklepod populati ons during the next three seasons compared to the nontreated control.