CORESTA Meeting, Agronomy/Phytopathology, 2017, Santa Cruz do Sul, APPOST 06

Soil applications of maleic hydrazide do not control tobacco axillary bud growth

North Carolina State University, Department of Crop & Soil Sciences, Raleigh, NC, U.S.A.

Increased focus on residues of the plant growth regulator Maleic Hydrazide (MH) have prohibited some U.S. producers from applying the suckercide to control tobacco axillary buds. As such, an alternative to the conventional foliar application of the material might prove beneficial to producers. Given that MH has systemic activity, reasoning might infer that soil application and root uptake might provide sufficient sucker control. To test this hypothesis, soil applications of MH at two rates (2.52 and 5.04 kg a.i./ha) were evaluated in four North Carolina environments. Soil applications of MH were preceded by two fatty alcohol (FA) applications and one flumetralin application or three fatty alcohol applications without flumetralin. A conventional treatment of foliar applied MH preceded by two applications of FA and one application of flumetralin was included for comparison. Foliar applications of all suckercides was delivered at 467 L/ha. Soil application volumes were similar to foliar and were delivered in two band applications to the soil surface adjacent to plants. Sucker control was similar between MH application rates and was greatest in the conventional foliar application method. In two Coastal Plain environments, the inclusion of flumetralin provided >89 % control. When the same treatment was evaluated in two Piedmont environments, efficacy was reduced by 30 to 50 %. In the absence of flumetralin, sucker control was further reduced in soil applied MH treatments, indicating that MH contribution to sucker control was minimal. Differences between the two MH application rates were not observed. Results indicate that soil applications of MH are unlikely to inhibit sucker growth as efficiently as conventional foliar applications and that the recommended foliar application rate of MH (2.52 kg a.i./ha) is sufficient for sucker suppression.