Sweet Corn Tolerance to Mesotrione

John M. Jemison, Jr., and Hilarie J. Wilson¹

ABSTRACT

Sweet corn growers have a very limited number of weed control products available that do not cause potential damage to crops planted the following year. In this trial, part of a multi-state effort this year, we assessed the possibility of using mesotrione pre and postemergence in sweet corn production. The project goals were to assess crop tolerance, influence on crop yield, and weed control. Five commonly grown sweet corn varieties of sweet corn were planted on 22 May 2002:  Silver Queen; Kandy Korn; Bodaceous; Prime Plus; and Serendipity. Aatrex (1 pt/ac) and Dual (1.5 pt/ac) were applied preemergence on five of eight weed control treatments. Mesotrione was applied preemergence in two forms:  s Camix (Callisto + Dual at 4.5 pts/ac) or as Lumax (Callisto + Atrazine + Dual at 5.6 pt/ac). We were also interested in evaluating sweet corn response to mesotrione applied at 3 oz/ac (recommended rate) with adjuvants and different sticker combinations. There were four postemergence treatments: mesotrione applied with urea-ammonium nitrate (UAN) and crop oil concentrate (COC) (2.5% and 1% v/v respectively); mesotrione with UAN and NIS (2.5% and 0.25% v/v, respectively); mesotrione with COC  (1% v/v), and mesotrione with atrazine and COC (0.25 lb ai/ac and 1% v/v). Evaluations were made at 7 and 18 days after treatment for numbers of injured plants as well as the amount of the plant expressing the injury. Total and marketable yield estimates were made at harvest.

Rainfall was adequate to activate the herbicides applied pre and postemergence. We saw no injury to any variety when mesotrione (Camix or Lumax) was applied preemergence. Early season weed control with the mesotrione premixes was excellent, particularly the three-way combination on nutsedge (Cyprus esculentus). We found significantly higher yields with Lumax and Camix compared to Bicep II magnum applied preemergence. A second flush of mustard in the bicep plots was sufficient competition for nutrients and water to negatively influence yield.  Injury from Lumax or Camix was negligible. There was significant injury to sweet corn from some of the postemergence treatments. The addition of the adjuvant UAN to any treatment caused significantly more injury to the corn, and the injury was visible throughout the year. Injury rating data collected at 18 DAT indicated that the plants treated with mesotrione with UAN and COC had 85% of the plants exhibiting injury on 6% of the plant compared to 1% of the plants exhibiting injury on less than 0.1% of the plant. In addition, marketable yield was reduced where UAN and COC were used in combination with 3 oz/ac of mesotrione. Use of COC or NIS alone did not cause significant injury or reduction in yield. It appears that inclusion of UAN on a sweet corn label should not be included if registration of mesotrione for sweet corn is pursued. This work and other similar projects this year have provided useful information on both the effectiveness of weed control with mesotrione and which adjuvant/sticker combinations are safe for the crop.

¹Extension Professor and Student Assistant – University of Maine Cooperative Extension, University of Maine, Orono, Maine