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Weeds are a top management concern among organic vegetable growers. Abrasive weeding is a nonchemical tactic using air-propelled abrasive grit to destroy weed seedlings within crop rows. Many grit types are effective, but if organic fertilizers are used, this could integrate weed and nutrient management in a single field pass. Our objective was to quantify the effects of abrasive grit and mulch type on weed suppression, disease severity, soil nitrogen availability, and yield of pepper (Capsicum annuum L. ‘Carmen’). A 2-year experiment was conducted in organic red sweet pepper at Urbana, IL, with four replicates of five abrasive grit treatments (walnut shell grits, soybean meal fertilizer, composted turkey litter fertilizer, a weedy control, and a weed-free control) and four mulch treatments (straw mulch, bioplastic film, polyethylene plastic film, and a bare soil control). Abrasive weeding, regardless of grit type, paired with bioplastic or polyethylene plastic mulch reduced in-row weed density (67 and 87%, respectively) and biomass (81 and 84%); however there was no significant benefit when paired with straw mulch or bare ground. Despite the addition of 6 to 34 kg N/ha/yr through the application of soybean meal and composted turkey litter grits, simulated plant N uptake was most influenced by mulch composition (e.g., plastic vs. straw) and weed abundance. Nitrogen immobilization in straw mulch plots reduced leaf greenness, plant height, and yield. Bacterial spot (Xanthomonas campestris pv. Vesicatoria) was confirmed on peppers in both years, but abrasive weeding did not increase severity of the disease. Pepper yield was always greatest in the weed-free control and lowest in straw mulch and bare soil, but the combination of abrasive weeding (regardless of grit type) and bioplastic or polyethylene plastic mulch increased marketable yield by 47% and 21%, respectively, compared with the weedy control. Overall, results demonstrate that when abrasive weeding is paired with bioplastic or polyethylene mulch, growers can concurrently suppress weeds and increase crop N uptake for greater yields.

Bacterial spot, caused by Xanthomonas cucurbitae, is an important disease of cucurbits worldwide. Considering the absence of resistant cultivars, along with the limited effects of chemical treatments, we evaluated the use of potential biocontrol agents for management of the disease. We collected 1,134 bacterial isolates associated with bacterial spot symptomatic leaves and fruits and screened in vitro for their antagonistic activity against X. cucurbitae. A total of 271 isolates inhibited colony formation of X. cucurbitae in a disc diffusion assay. Species of these antagonistic isolates were identified based on 16S rRNA primers and phylogenetic analysis using four housekeeping genes. Based on results from the in vitro assays, the strong inhibitors of X. cucurbitae were selected for greenhouse and field evaluations. We found that Bacillus amyloliquefaciens, Bacillus velezensis, Pantoea agglomerans, and Pseudomonas putida were able to prevent or limit development of bacterial spot on pumpkin plants in the greenhouse and field studies. Additionally, Bacillus amyloliquefaciens and Pseudomonas putida increased growth of ‘Howden’ pumpkin (Cucurbita pepo). Our results suggest that these biocontrol agents can be used for managing bacterial spot disease and enhancing the growth of pumpkin plants.