2019 ASHS Annual Conference

Many pumpkins in the Midwest are grown using conservation tillage practices, with no-tillage and strip-tillage systems most often utilized. The implementation of conservation tillage systems by pumpkin growers has been somewhat limited due to the lack of effective weed control options, since tillage is widely used in conventional tillage systems for weed control prior to vining. Although weed control is improved with cover crop residues, season-long weed control is difficult to achieve in pumpkin conservation tillage systems due to the lack of sufficient herbicides to provide adequate control. A pre-emergence herbicide evaluation was conducted in no-tillage during 2009 and 2010 using only those specifically labeled for pumpkins to determine the benefits associated with specific herbicide combinations and the return on investment associated with their use. The recommended herbicides and rates (g ai^.ha^-1) used were: clomazone (350) + ethalfluralin (1,120); halosulfuron (35); and metalochlor (1,356). The primary weed species present were common waterhemp (Amaranthus rudis), redroot pigweed (A. retroflexus), giant foxtail (Setaria faberi), and large crabgrass (Digitaria sanguinalis). Results over both growing seasons indicated that metalochlor applied in combination with clomazone + ethalfluralin provided an increased return on investment compared to other pre-emergence treatments evaluated, which included metalochlor alone and in combination with halosulfuron, as well as clomazone + ethalfluralin alone and in combination with halosulfuron. Those with the lowest return on investment were metalochlor combined with halosulfuron and clomazone + ethalfluralin combined with halosulfuron. Besides providing the highest returns on investment, the pre-emergence application of metalochlor with clomazone + ethalfluralin also tended to produce the pumpkin fruit with the greatest size and diameter under the weed species present.