Aminocyclopyrachlor Efficacy for Non-Cropland Weed Control

The production of chemicals for crop protection purposes evolved after World War II with the commercialization of the auxin herbicides 2,4-D and MCPA. Their utility and effectiveness created an interest for North American and European companies to develop and research thousands of agrochemicals available today.

Recently discovered and introduced to the market by DuPont Crop Protection, aminocyclopyrachlor is the first broad spectrum synthetic auxin herbicide in this chemical class, and is structurally similar to the auxin herbicides: aminopyralid, clopyralid and picloram. Aminocyclopyrachlor has activity on broadleaf weed species with limited activity on monocot species. Aminocyclopyrachlor is absorbed via plant roots and foliage and translocates to meristematic areas. Affected plants exhibit epinasty, stem twisting, cupping of new leaves and damaged vascular systems typical of synthetic auxin herbicides.

Laboratory and greenhouse studies were established to evaluate biokinetics and efficacy of ¹⁴C-aminocyclopyrachlor-methyl ester [Carbon-14 aminocyclopyrachlor-methyl ester] alone and in mixture with diflufenzopyr for control of black nightshade (Solanum nigrum L.) and large crabgrass [Digitaria sanguinalis (L.) Scop.]. Field studies were conducted to evaluate efficacy of aminocyclopyrachlor for Japanese honeysuckle (Lonicera japonica Thunb.) control in a pastures.

Overall, ¹⁴C-aminocyclopyrachlor-methyl ester absorption was greater in large crabgrass than in black nightshade, while translocation in large crabgrass was lower than in black nightshade. Translocation in both large crabgrass and black nightshade was primarily to the rest of foliage and above treated leaf plant sections. In both species, metabolism of ¹⁴C-aminocyclopyrachlor-methyl ester was rapid, as 60 to 78% of radioactivity detected by 8 hours after treatment was the free acid metabolite in both weed species.

In the field, aminocyclopyrachlor demonstrated utility for managing Japanese honeysuckle in abandoned pasture fields when applied alone and in combination with other herbicides. For example, 2,4-D and metsulfuron controlled Japanese honeysuckle 42 to 68% by 52 weeks after treatment (WAT). Japanese honeysuckle control with aminopyralid and diflufenzopyr applied alone was ≤ 35%. Inclusion of aminocyclopyrachlor (70 g ha^-1) [grams of weight in hectare] increased Japanese honeysuckle control with 2,4-D to 83 to 92%, similar to aminocyclopyrachlor alone at 280 g ha^-1 (85 to 90% control).