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CORESTA Meeting, Agronomy/Phytopathology, 2013, Brufa di Torgiano, AP 02

Factors impacting maleic hydrazide residues on flue-cured tobacco

REED T.D.
Virginia Tech, Southern Piedmont Agricultural Research and Extension Center, Blackstone, VA, U.S.A.

Maleic hydrazide (MH) remains an important compound for efficient, cost effective sucker control for flue-cured tobacco production in the U.S. Minimizing MH residues in cured tobacco is critical to maintaining the demand for U.S leaf in international markets. The objective of on-going research at the Virginia Tech Southern Piedmont Center is to develop best management practices (BMPs) for the use of MH on flue-cured tobacco. Such strategies include: the application of reduced MH rates, better understanding plant factors impacting MH residues, low volume wash-off treatments, and alternative application techniques. One study investigated the impact of time-of-day for MH application (8:00 a.m., noon, and 4:00 p.m.) and timing of the application in relation to first priming (prior to, shortly after, and delayed). Green leaf tissue was periodically sampled to quantify the natural weathering of MH residues from rainfall as well as the corresponding cured leaf. A second study investigated the impact of low volume wash-off application on MH residues. Wash-off application volumes of 560 and 1680 L/ha were compared at both 2 and 6 hours after MH application. Data from 2012 demonstrated significantly lower MH residues following a wash-off rate of 1680 L/ha applied at 2 or 6 hours. Sucker control was not adversely affected by the low volume wash-off applications. The “conveyor” sucker control application technique produces a concentrated spray pattern of very coarse droplets. Comparisons were made of three rates of MH made with and without the conveyor spray hoods. Treatments were evaluated for green leaf residues the day after application, cured leaf residues on both cutter and tip leaves, and sucker control. Results of the above research should provide BMPs necessary to allow growers to continue to use MH for effective sucker control and provide tobacco minimal residues.