Field experiments were conducted to determine weed control and radish (Raphanus sativus) response to S-metolachlor on organic soil in the Everglades Agricultural Area (EAA) using a dose–response bioassay. S-metolachlor was applied preemergence at 0.35, 0.7, 1.4, 2.8, 5.6, and 11.2 kg·ha−1. The rate of S-metolachlor required to provide 90% weed control (ED90) and result in 5% and 10% radish injury were determined by fitting a three-parameter log-logistic model. The ED90 values for common lambsquarters, spiny amaranth, and fall panicum control were 2.7, 1.6, and 1.2 kg·ha−1 of S-metolachlor, respectively, at 14 days after treatment (DAT). At 28 DAT, the ED90 values were 3.8, 1.9, and 1.5 kg·ha−1 of S-metolachlor, respectively. Injury on radish increased as S-metolachlor rates increased with maximum injury of 24% and 19% at 14 and 28 DAT, respectively. S-metolachlor at 2.1 and 3.1 kg·ha−1 at 14 DAT and 2.6 and 3.7 kg·ha−1 at 28 DAT would result in 5% and 10% radish injury, respectively. Radish yield decreased with increasing rates of S-metolachlor. At the proposed S-metolachlor use rate of 1.4 kg·ha−1 for root crops, radish yield was 80% of the weed-free yield probably resulting from competition from common lambsquarters, which was controlled 74%. These results show that preemergence S-metolachlor would provide effective control of spiny amaranth and fall panicum in radish on organic soils of the EAA at the proposed use rate for root crops while about three times the proposed use rate would be required to provide effective common lambsquarters control. This implies that infestation of common lambsquarters on radish fields on organic soils will not be effectively controlled by S-metolachlor at the proposed use rate resulting in yield reduction.
Dennis C. Odero, Jose V. Fernandez and Nikol Havranek
Gary E. Vallad, Kenneth L. Pernezny, Botond Balogh, Aimin Wen, Jose Francisco L. Figueiredo, Jeffrey B. Jones, Timur Momol, Rosa M. Muchovej, Nikol Havranek, Nadia Abdallah, Steve Olson and Pamela D. Roberts
Studies were conducted at three locations in Florida to evaluate the effects of kasugamycin alone, in alternation, or as a tank-mix partner with copper bactericides and other fungicides against bacterial spot of tomato. In greenhouse trials, kasugamycin, formulated as Kasumin® 2L, reduced bacterial spot severity by up to 37.5% compared with a non-treated control. Little advantage in disease control was observed by mixing kasugamycin with other fungicides. Kasugamycin was assessed in six field trials. In the four field trials that tested kasugamycin alone, it was as effective as the standard copper + mancozeb treatment for the control of bacterial spot. In four trials, no benefit was observed in applying kasugamycin as a mixture with copper + mancozeb, and only one of three trials did alternating kasugamycin with copper + mancozeb improve bacterial spot control over either the copper + mancozeb standard or kasugamycin alone. Although kasugamycin was effective for the control of bacterial spot in greenhouse and field trials, rapid development of resistance in field populations of X. perforans may shorten the effective use of this antibiotic.