Joshua H. Freeman

Host Plant Preference of Harlequin Bug (Hemiptera: Pentatomidae), and Evaluation of a Trap Cropping Strategy for its Control in Collard

ABSTRACT Harlequin bug, Murgantiahistrionica (Hahn) (Hemiptera: Pentatomidae),is a piercingsucking pest of cole crops, causing cosmetic damage in low populations, while heavy pest pressure can kill plants or entire fields. Field studies were conducted to evaluate a trap crop for control of harlequin bug in collard. Field-cage choice tests found that potential trap crop plant species, mustard (Brassica juncea ‘Southern Giant Curled’), rapeseed (B. napus ‘Athena’), rapini (B. rapa), and arugula (Eruca sativa) attracted more harlequin bugs than collard (B. ohraeea ‘Champion’) and a nonbrassica control, bean (Phaseolus vulgaris ‘Bronco’). Mustard was the most consistently selected by harlequin bug over collard in choice tests, and was found to be an effective trap crop for reducing feeding injury on collard at two experimental sites. Augmentation of the mustard trap crop with a systemic, neonicotinoid insecticide provided no added control of harlequin bug for the 10 wk duration in the spring season.

Yellow Nutsedge (Cyperus esculentus) Control with Reduced Rates of Dimethyl Disulfide in Combination with Totally Impermeable Film

Abstract Methyl bromide (MBr) was widely used as a soil fumigant to manage pests in the planting bed prior to transplanting fresh market tomato; however, it has been banned by the United Nations Environment Programme. Alternatives to MBr must be implemented to sustain productivity in fresh market tomato. Dimethyl disulfide plus chloropicrin (DMDS : Pic) is a fumigant alternative to methyl bromide for the management of yellow nutsedge and other soil-borne pests in tomato. Fumigant costs, environmental concerns, and risk mitigation measures encourage reduced fumigant application rates. Virtually impermeable film (VIF) and totally impermeable film (TIF) provide greater fumigant retention than low density and high density polyethylene film, VIF and TIF can allow for reduced fumigant application rates while maintaining fumigant efficacy. The objectives of this research were to evaluate TIF with reduced rates of shank-applied DMDS : Pic (79 : 21 w/w) for the control of yellow nutsedge in tomato. Treatments included a standard rate of DMDS : Pic (468 L ha−1) under VIF and TIF, a high rate (561 L ha−1) under VIF, three reduced rates (187 L ha−1, 281 L ha−1, and 374 L ha−1) under TIF, and a nontreated control under TIF and VIF. Results indicated rates may be reduced from a standard 468 L ha−1 under VIF to 187 L ha−1 (67% reduction) under TIF while maintaining yellow nutsedge control and tomato yields. In addition, the results indicated that nontreated TIF managed yellow nutsedge better than nontreated VIF because of decreased penetration of the mulch by yellow nutsedge. Nomenclature: Dimethyl disulfide; chloropicrin; yellow nutsedge; Cyperus esculentus L.; tomato; Solanum lycopersicum L. Resumen Methyl bromide (MBr) fue ampliamente usado como fumigante de suelo para manejar plagas en las camas de siembra previamente al trasplante de tomate para el mercado fresco. Sin embargo, este fumigante fue prohibido por el Programa para el Ambiente de las Naciones Unidas. Alternativas a MBr deben ser implementadas para mantener la productividad del tomate para mercado fresco. Dimethyl disulfide más chloropicrin (DMDS:Pic) es un fumigante alternativo a methyl bromide para el manejo de Cyperus esculentus y otras plagas de suelo del tomate. Los costos de fumigación, las preocupaciones ambientales, y las medidas de mitigación de riesgo promueven el uso de dosis reducidas en aplicaciones de fumigante. Coberturas plásticas con películas virtualmente impermeables (VIF) y totalmente impermeables (TIF) brindan mayor retención del fumigante que coberturas de polyethylene de baja y alta densidad, lo que permitiría el uso de dosis reducidas de fumigante al tiempo que se mantendría la eficacia del fumigante. Los objetivos de esta investigación fueron evaluar TIF con dosis reducidas de DMDS:Pic (79:21 w/w) aplicadas con inyector de cincel para el control de C. esculentus en tomate. Los tratamientos incluyeron una dosis estándar de DMDS:Pic (468 L ha−1) bajo VIF y TIF, una dosis alta (561 L ha−1) bajo VIF, tres dosis reducidas (187 L ha−1, 281 L ha−1, y 371 L ha−1) bajo TIF, y un testigo sin tratamiento bajo TIF y VIF. Los resultados indicaron que las dosis pueden ser reducidas de 468 L ha−1 a 187 L ha−1 (una reducción del 67%) bajo TIF al tiempo que se mantienen el control de C. esculentus y el rendimiento del tomate. Adicionalmente, los resultados indicaron que en los testigos sin fumigación, el TIF controló mejor C. esculentus que VIF debido a una menor penetración de la maleza a través de la cobertura.

Foliar Applications of Acibenzolar-S-Methyl Negatively Affect the Yield of Grafted Tomatoes in Fields Infested with Ralstonia solanacearum

Three field experiments were conducted in Florida from 2012-2014 to assess the impact of acibenzolar-S-methyl (ASM), a systemic acquired-resistance inducer, applied as foliar spray or through drip-irrigation lines, on bacterial wilt incidence and yield of grafted tomatoes. The experiments were conducted in a field with race 1, biovar 1 strain of Ralstonia solanacearum, causal agent of tomato bacterial wilt. In all three experiments, the susceptible tomato variety BHN 602, grafted onto a resistant rootstock BHN 998, was compared with nongrafted BHN 602, treated with or without foliar applications of ASM and with grafted plants treated with foliar applications of ASM. In two experiments, an additional treatment of drip applications of ASM on grafted and nongrafted plants was evaluated. Grafting alone or in combination with drip applications of ASM (178.6 μM) significantly reduced disease incidence and increased total marketable yield relative to nongrafted treatments. There were no significant differences between grafted plants with or without drip ASM applications in terms of bacterial wilt incidence or total marketable yield. However, we demonstrate for the first time that foliar ASM applications on grafted plants negatively affects the total marketable yield compared with drip ASM applications on grafted plants or nontreated grafted control.

Yellow Nutsedge (Cyperus esculentus) Control with Methyl Iodide in Combination with Totally Impermeable Film

Abstract Methyl bromide (MBr) has been an industry standard for soil fumigation in a multitude of crops for decades. However, it has been banned by the United Nations Environment Programme, and alternatives to MBr must be implemented to sustain productivity in many vegetable crops that depend on soil fumigation. One alternative that has been implemented in some areas is methyl iodide (MeI). Efficacy of MeI has been demonstrated on many pest species and has been generally similar to MBr. Methyl iodide is a costly material, which has likely limited its adoption. Virtually impermeable film (VIF) and totally impermeable film (TIF) provide greater fumigant retention than low-density and high-density polyethylene film, which can allow for reduced fumigant application rates while maintaining fumigant efficacy. The objectives of this research were to evaluate TIF with reduced rates of shank-applied MeI : chloropicrin (Pic) (50 : 50 w/w) for the control of yellow nutsedge in tomato. Treatments included a standard rate of MeI : Pic (93.3 L ha−1 [178 kg ha−1 broadcast]) under VIF and TIF, three reduced rates (37.3, 56, 74.6 L ha−1 [71.2, 106.8, 142.5 kg ha−1 broadcast, respectively]) under TIF, and a nontreated control under TIF. Results indicate fumigant use rates may be reduced from a standard 93.3 L ha−1 under VIF to 37.3 L ha−1 (60% reduction) under TIF while providing yellow nutsedge control and maintaining tomato yields. Nomenclature: Methyl iodide; chloropicrin; yellow nutsedge, Cyperus esculentus L.; tomato, Solanum lycopersicum L. Resumen Methyl bromide (MBr) ha sido el estándar de la industria para la fumigación de suelo en múltiples cultivos por décadas. Sin embargo, debido a que ha sido prohibido por el Programa para el Ambiente de las Naciones Unidas, alternativas a MBr deben ser implementadas para mantener la productividad de muchos vegetales que dependen de la fumigación del suelo. Una alternativa que ha sido implementada en varias áreas es methyl iodide (MeI). La eficacia de MeI ha sido demostrada en muchas especies de plagas y ha sido generalmente similar a MBr. Methyl iodide es un material costoso, lo que probablemente ha limitado su adopción. Coberturas virtualmente impermeables (VIF) y coberturas totalmente impermeables (TIF) brindan mayor retención del fumigante que las coberturas de polyethylene de baja o alta densidad, lo que permite el uso de dosis reducidas de fumigante manteniendo su eficacia. Los objetivos de esta investigación fueron evaluar TIF con dosis reducidas inyectadas al suelo de MeI:chloropicrin (Pic) (50:50 w/w) para el control de Cyperus esculentus en tomate. Los tratamientos incluyeron una dosis estándar de MeI:Pic (93.3 L ha−1 [178 kg ha−1 aplicación generalizada]) bajo VIF y TIF, tres dosis reducidas (37.3, 56, 74.6 L ha−1 [71.2, 106.8, 142. 5 kg ha−1 aplicación generalizada, respectivamente]) bajo TIF y un testigo no tratado bajo TIF. Los resultados indican que las dosis de fumigante pueden ser reducidas desde el estándar 93.3 L ha−1 bajo VIF a 37.3 L ha−1 (reducción del 60%) bajo TIF al tiempo que se obtiene el control de C. esculentus y se mantiene el rendimiento del tomate.

Nitrogen Fertilizer and Growth Regulator Impacts on Tuber Deformity, Rot, and Yield for Russet Potatoes

Potatoes (Solanum tuberosum) are an important high-value commodity for producers in the Mid-Atlantic Region. Current production recommendations were based on white potatoes, and practices for Russet potatoes have not been researched in this region. The objective of this study was to test impacts of N rate (0, 67, 134, 201, and 268 kg N ha−1), N application timing (100% applied with planter, 2-way split (30% with planter and 70% band applied approximately 30 days after planting at dragoff), and three-way split (30% with planter, 50% band applied prior to drag-off, and 20% band applied at first sight of bloom)), and additions of the growth regulator maleic hydrazide (MH-30). We tested “Goldrush” and “Norkotah” Russet potato varieties on marketability, total yield, tuber deformity, and tuber soft rot incidence for sandy loam soils in the Mid-Atlantic. Overall, year variations were significant with substantial rots (up to 86.5%) occurring in year 3. Maleic hydrazide and N application timing had little consistent effect on any tested parameter. Nitrogen rate and variety factors had the greatest impacts on deformity, tuber rots, and yields for Russet potatoes in the Mid-Atlantic Region with 134 kg N ha−1 producing the highest total yields in 2009 and 2010. If tuber rots can be controlled, both “Goldrush” and “Norkotah” are acceptable varieties under the Mid-Atlantic production practices.

Epidemiology and management of bacterial leaf spot on watermelon caused by Pseudomonas syringae

Bacterial leaf spot of watermelon caused by Pseudomonas syringae has been an emerging disease in the southeastern United States in recent years. Disease outbreaks in Florida were widespread from 2013 to 2014 and resulted in foliar blighting at the early stages of the crop and transplant losses. We conducted a series of field trials at two locations over the course of two years to examine the chemical control options that may be effective in management of this disease, and to investigate the environmental conditions conducive for bacterial leaf spot development. Weekly applications of acibenzolar-S-methyl (ASM) foliar, ASM drip, or copper hydroxide mixed with ethylene bis-dithiocarbamate were effective in reducing the standardized area under the disease progress curve (P < 0.05). Pearsons correlation test demonstrated a negative relationship between the average weekly temperature and disease severity (-0.77, P = 0.0002). When incorporated into a multiple regression model with the square root transformed average weekly rainfall, these two variables accounted for 71% of the variability observed in the weekly disease severity (P < 0.0001). This information should be considered when choosing the planting date for watermelon seedlings as the cool conditions often encountered early in the spring season are conducive for bacterial leaf spot development.