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  • Author or Editor: Brian J. Schutte x
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Soil-borne diseases and weeds can be inhibited by mustard family (Brassicaceae) cover crops that are mowed and incorporated into the soil with tillage—a process referred to as biofumigation. To determine whether a fall-seeded mustard cover crop produces enough biomass to be a biofumigant in spring, this study measured the amount of biomass produced by a mixture of ‘Caliente Rojo’ brown mustard (Brassica juncea) and ‘Nemat’ arugula (Eruca sativa) grown in three commercial fields and a university research farm in southern New Mexico, USA. This study also determined whether the mustard biomass incorporated in the soil inhibits a weed [Palmer amaranth (Amaranthus palmeri)], but does not affect a cash crop adversely [chile pepper (Capsicum annuum)]. Results indicated that, if the mustard cover crop was seeded before the first frost in fall, mustard cover crops produced biomass in quantities sufficient for biofumigation in spring. Mustard biomass incorporated in the soil reduced the survival and germination of Palmer amaranth seeds. Under greenhouse conditions, chile pepper plants grown in soil with mustard cover crop biomass were larger than chile plants grown in soil without mustard biomass. Chile pepper plants in soil with mustard biomass did not show symptoms of Verticillium wilt (Verticillium dahliae), whereas such symptoms were found on about 33% of chile pepper plants in soil without mustard biomass. These results suggest that a fall-seeded mustard cover crop that is tilled into the soil in early spring is a potential pest management technique for chile pepper in New Mexico.

Open Access

Seaside petunia (Calibrachoa parviflora) is a mat-forming plant species that was recently reported in fall-seeded onion (Allium cepa) in the southwestern United States. To initiate development of herbicide recommendations for seaside petunia in onion, we conducted a study to determine seaside petunia susceptibility to commonly used herbicides for broadleaf weed control after onion emergence. Our study included herbicides applied at below-label rates, which provided insights on seaside petunia responses to reductions in the amount of herbicide available for plant absorption. For herbicides with preemergence activity, our growth chamber study indicated that soil applications of flumioxazin or oxyfluorfen (0.06 and 0.25 lb/acre, respectively) prevented seaside petunia seedling emergence when applied at 0.125×, 0.25×, 0.5×, and 1.0× the labeled rates for onion. Labeled rate treatments of dimethenamid-P (0.84 lb/acre) and S-metolachlor (0.64 lb/acre) inhibited seedling emergence similar to labeled rate treatments of flumioxazin and oxyfluorfen; however, below-label rate treatments of dimethenamid-P and S-metolachlor resulted in diminished control of seaside petunia compared with the labeled rate treatments. Following labeled rate applications of dimethyl tetrachloroterephthalate [DCPA (6 lb/acre)] and pendimethalin (0.71 lb/acre), more than 50% of seaside petunia seedlings emerged compared with the nontreated control. For herbicides with postemergence activity on weeds, our greenhouse study indicated that bromoxynil at 0.37 lb/acre, flumioxazin at 0.06 lb/acre, and oxyfluorfen at 0.25 lb/acre equally reduced growth of seaside petunia plants that were small at the time of spraying (stem length, 1–2 cm). Postemergence control of seaside petunia with oxyfluorfen and flumioxazin decreased as plant size at spraying increased; however, bromoxynil effects on seaside petunia remained high as stem length at spraying increased from 5 to 12 cm. Based on the results of this study, we conclude that promising herbicide programs for seaside petunia in onion include oxyfluorfen or flumioxazin for preemergence control and bromoxynil for postemergence control. These herbicides, alone and in combination, should be evaluated for seaside petunia control and onion phytotoxicity in future field trials.

Open Access

This study evaluated false seedbeds, which are sequences of irrigation and tillage that eliminate weed seedlings before crop planting, to reduce requirements for hand hoeing in chile pepper (Capsicum annuum). To address this objective, a field study was conducted near Las Cruces, NM from July 2015 to Oct. 2016 (experimental run 1) and July 2016 to Oct. 2017 (experimental run 2). False seedbeds were designed to target weeds that typically emerge after chile pepper planting. This was done by implementing false seedbeds the summer before chile pepper seeding. During chile pepper seasons, data included repeated measures of weed seedling emergence, amounts of time required for individuals to hoe field sections (i.e., hoeing time), and yields of two chile products: early harvest of green fruit and late harvest of red fruit. Hoeing time and yield data were included in cost–benefit analyses that also incorporated expenses and revenues projected by crop budget models for the study region. Results indicated false seedbeds caused a 54% decrease in weed population density during the chile pepper season of experimental run 1; however, for experimental run 2, false seedbeds did not affect cumulative weed seedling emergence. For both experimental runs, false seedbeds reduced hoeing times, suggesting that false seedbeds affected hoeing by means other than reduced weed density. After accounting for costs for implementation, false seedbeds reduced hand hoeing costs by $262/acre to $440/acre. These reductions in hoeing costs coincided with improved profitability in all but one combination of year and product. Green fruit yield was lower in false seedbed plots in experimental run 1; however, false seedbeds did not affect green fruit yield in experimental run 2, or red fruit yield in both experimental runs. These results indicate that false seedbeds implemented the summer before planting are promising techniques for reducing labor requirements for weeding in chile pepper production.

Open Access

Overwinter mustard cover crops incorporated into soil may suppress early-season weeds in chile pepper (Capsicum annuum). However, the potential for mustard cover crops to harbor beet leafhoppers (Circulifer tenellus) is a concern because beet leafhoppers transmit beet curly top virus to chile pepper. The objectives of this study were to determine the amounts of a biopesticidal compound (sinigrin) added to soil from ‘Caliente Rojo’ brown mustard (Brassica juncea) cover crops ended on three different days before beet leafhopper flights during spring and to determine the effects of the cover crop termination date on weed densities and hand-hoeing times for chile pepper. To address these objectives, a field study was conducted in southern New Mexico. In 2019–20, the cover crop was ended and incorporated into soil 45, 31, and 17 days before beet leafhopper flights. In 2020–21, cover crop termination occurred 36, 22, and 8 days before beet leafhopper flights. Treatments also included a no cover crop control. Cover crop biomass and sinigrin concentrations were determined at each termination. Chile pepper was seeded 28 days after the third termination date. Weed densities and hand-hoeing times were determined 28 and 56 days after chile pepper seeding. In 2019–20, the third termination (17 days before beet leafhopper flights) yielded the maximum cover crop biomass (820 g⋅m−2) and greatest sinigrin addition to soil (274 mmol⋅m−2). However, only the second termination (31 days before beet leafhopper flights) suppressed weeds in chile pepper. In 2020–21, the third termination (8 days before beet leafhopper flights) yielded the maximum cover crop biomass (591 g⋅m−2) and greatest sinigrin addition to soil (213 mmol⋅m−2), and it was the only treatment that suppressed weeds. No cover crop treatment reduced hand-hoeing times. These results indicate that overwinter mustard cover crops can be ended to evade beet leafhopper flights and suppress weeds in chile pepper.

Open Access