Weed management in cantaloupe and other melon crops is important to maximize fruit yield; however, there are few registered herbicides available in California. Several independent herbicide trials were conducted at University of California field stations in Davis (Yolo County), Five Points (Fresno County), and Holtville (Imperial County) from 2013 to 2019 to evaluate both registered and unregistered herbicides and incorporation methods (sprinklers, cultivation, or none) for crop safety and weed control in melons. Although specific treatments varied among locations depending on local practice and research objectives, ethalfluralin and halosulfuron were used in all experiments, and bensulide and S-metolachlor were evaluated in 4 of 6 site-years. Additional herbicides included clethodim, clomazone, DCPA, napropamide, pendimethalin, sethoxydim, and sulfentrazone. Among registered herbicides, halosulfuron, halosulfuron + ethalfluralin, and ethalfluralin + bensulide combinations provided consistently beneficial weed control across all site-years compared to the nontreated control. S-metolachlor performed as well as the best of the registered herbicides tested at each site-year; although moderate injury was noted at the Davis location, this did not reduce melon yield. The method used to incorporate preplant herbicides had a significant impact on weed control efficacy but varied by location. Mechanical incorporation of preplant herbicides resulted in improved weed control and yield compared to sprinklers. Early-season weed control, whether by herbicides or hand weeding, resulted in significant yield increase in most site-years.

Field trials were conducted at the Coastal Plain Experiment Station in Tifton, GA, from 2000 to 2003 to study the effects of herbicide placement on weed control and cantaloupe injury. Herbicides halosulfuron (0.036 kg ai/ha), sulfentrazone (0.14 and 0.28 kg ai/ha), clomazone (0.6 kg ai/ha), and a nontreated control were evaluated. Methods of herbicide application were preplant incorporated (PPI) under the polyethylene mulch before transplanting, posttransplanting over-the-top (POST-OTT), and posttransplanting-directed (POST-DIR) to the shoulders of polyethylene-covered seedbeds. Across all herbicide treatments, PPI and POST-DIR applications were the least injurious, with POST-OTT applications the most injurious. In general, sulfentrazone (0.28 kg ai/ha) was the most injurious herbicide and halosulfuron the least injurious, regardless of herbicide placement. Halosulfuron effectively controlled yellow nutsedge and provided versatility in methods of application, with minimal injury to transplanted cantaloupe.

Cantaloupe and watermelon growers in the southeastern United States use a system of hybrid transplants grown on narrow low-density polyethylene (LDPE) mulch-covered seedbeds with overhead irrigation and use the mulch cover for only one crop. LDPE mulches are costly to remove from the field and dispose. Biodegradable mulches that eliminate removal and disposal costs would be of significant benefit, provided that weeds are adequately suppressed. Cotton gin trash is a biodegradable waste product, composed of fiber fragments and seed pieces. Using a proprietary process, cotton gin trash can be chopped, pressed, and heated into a loose mat and stored on a continuous roll. Preliminary studies were conducted in 2010 and 2011 to determine if rolled cotton fiber mulch made from gin trash could be applied as a seedbed cover using conventional application equipment and adequately suppress weeds. Mulching materials (rolls 91 cm wide) were applied with a mulch layer that produced a finished seedbed 40 cm wide. ‘Athena' cantaloupe and ‘Crimson Sweet' watermelon were transplanted using a waterwheel transplanter. Mulching materials included rolled cotton fiber mulch sprayed with boiled linseed oil after mulch application, rolled cotton fiber mulch sprayed with black latex paint, black LDPE, and bare ground. Herbicide treatments included ethalfluralin, halosulfuron, and glyphosate applied as directed spray and nontreated with herbicides. Rolled cotton fiber mulch was easily applied with a conventional mulch layer with no modification and minimal adjustment, producing no tears or holes. Biodegradable cotton fiber mulch treated with boiled linseed oil or black latex paint suppressed weeds equally well as LDPE and all were better than bare-ground plots. Herbicides improved control of all weeds over the nontreated control and this effect was independent of weed suppression provided by seedbed mulches. Cantaloupe and watermelon yields were not affected by seedbed mulches, but were increased by weed control provided by herbicides.

Studies were conducted from 1998 to 2001 in Tifton, GA, on weed management systems in transplanted cantaloupe and watermelon grown on polyethylene-covered seedbeds. Soil fumigants were metham (748 L/ha) and a nonfumigated control. All metham applications were sprayed in a 61-cm band and incorporated with a modified power tiller. Herbicide treatments were ethalfluralin (0.8 kg ai/ha) premergence (PRE), ethalfluralin plus halosulfuron (36 g ai/ha) PRE, ethalfluralin PRE followed by glyphosate (1.1 kg ai/ha) postemergence POST-SHIELDED, ethalfluralin plus halosulfuron PRE followed by glyphosate POST-SHIELDED, and a nontreated control. Premergence herbicides were directed to row middles not covered in polyethylene, without contacting the transplants. Glyphosate was applied to row middles using a hooded sprayer, just before vine running. Overall weed control was not improved with soil fumigation in either cantaloupe or watermelon, and there was no yield response in either crop. There may be minimal benefit in transplanted cantaloupe and watermelon on polyethylene-covered seedbeds from preplant soil fumigation for weed control, in the absence of other pests. Herbicide systems that included halosulfuron PRE or glyphosate applied POST-SHIELDED improved control of yellow nutsedge compared with ethalfluralin alone. Control of Texas panicum, southern crabgrass, Florida pusley, and smooth pigweed was not improved by halosulfuron or glyphosate. Polyethylene-covered seedbeds provide a mechanical barrier to weed infestation for many species. Integration of these weed control practices gives cantaloupe and watermelon growers effective options for weed management, particularly for a troublesome species such as yellow nutsedge.

Intercropping cantaloupe and cotton can improve grower profits over traditional monoculture practices because crops share resources and production costs. However, developing effective programs to control weeds with herbicides that are safe to both crops can be challenging. Research was conducted to (1) identify herbicide systems to manage Palmer amaranth in cantaloupe–cotton intercropping production while minimizing crop injury, and (2) determine the profitability of cantaloupe–cotton intercropping. Ethalfluralin applied preplant did not injure cantaloupe or cotton, but Palmer amaranth was not controlled. The addition of fomesafen preplant improved Palmer amaranth control to at least 92% without injuring cotton, but cantaloupe necrosis and chlorosis of up to 20% was recorded. Halosulfuron-methyl was safely applied over cantaloupe, but its residual activity reduced cotton growth by 12% at 4 wk after planting; halosulfuron-methyl did not improve Palmer amaranth control beyond that noted with ethalfluralin plus fomesafen preplant. Intercropping systems that controlled Palmer amaranth at least 92% produced cantaloupe yields (25,760 to 25,890 fruit ha−1) similar to the weed-free monoculture system (24,120 fruit ha−1) but produced lint cotton yields that were 170 to 275 kg ha−1 less than the weed-free monoculture cotton system. Although cotton production was less in the intercropping system, the returns over variable costs with intercropping systems ($21,670 to 21,920 ha−1) exceeded those of cantaloupe monoculture ($18,070 ha−1) or cotton monoculture ($1,890 to $1,955 ha−1), as long as Palmer amaranth was controlled. Intercropping cantaloupe and cotton is an effective approach to share land resources and production inputs as well as to improve grower profitability and is being rapidly adopted by Georgia growers.