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Polycultures, mixtures of different crop species in the same field, may provide both production and ecological benefits. Silage production in annual cropping systems may incorporate polycultures and take advantage of species’ niche partitioning, potentially stabilizing yield variation due to abiotic stress. Using maize (Zea mays L.) silage as the basis of our 3‐year study, we tested the impact on crop and soil attributes of replacing a fraction of maize with soy (Glycine max (L.) Merr.), sorghum (Sorghum bicolor var. bicolor × bicolor and var. sudanense [unnamed hybrid]), or a medley of soy, sorghum, and sunflower (Helianthus annuus L.). Compared to maize monocultures and on average for the three years, a replacement mixture of maize + soy lowered yields(1.57 vs. 1.87 kg m‐2), but increased the nitrogen (N), phosphorus (P), and potassium (K) concentration in the silage by 1.2x, 1.09x, and 1.03x, respectively. Maize + sorghum polycultures matched the biomass yields of maize monocultures (1.77 vs. 1.87 kg m‐2) and increased K concentration (10.2 vs. 8.2 g kg‐1). While random forest analysis revealed no change in post‐harvest soil mineral N with depth among treatments, there was a tendency for higher total mineral N left in the soil for soy‐containing vs. sorghum‐containing treatments (12.4 vs. 10.9 g m‐2). Silage polycultures are a feasible alternative to maize silage monocultures and can improve silage nutrient concentration with no yield penalty if maize or sorghum dominate plant stands. This article is protected by copyright. All rights reserved

Hydrilla verticillatais an aquatic weed that grows densely throughout the water column and is costly to manage. The hydrilla tip mining midge,Cricotopus lebetis, a potential augmentative biological control agent of hydrilla, feeds on the apical meristem preventing growth. The goal of this study was to quantify the influence of a predator (mosquitofish,Gambusiasp.) and a competitor (hydrilla leafcutter moth,Parapoynx diminutalis) and their interactions, on the ability of the midge to survive and feed on hydrilla. The first experiment involved six treatments established in 37.8 L tanks with combinations of the organisms, including larvalC. lebetis. Survival to adult midge eclosion was significantly reduced in the presence of the predator but was unaffected by the competitor’s presence alone. Apical meristem damage was reduced when both the competitor and predator were present. The second experiment included four treatments withC. lebetisegg masses or larvae and the presence or absence of mosquitofish. AddingC. lebetisas eggs rather than as larvae increased midge survival in the absence of the predator. Midge survival was lower when larvae were added, but the predator had no additional effect. To facilitate successful establishment of the midge and control of hydrilla, high numbers of larvae should be released to overcome predation.

Background Mosquito larvicides provide a source-reduction strategy to diminish adult females that bite and potentially spread pathogens. Demands are mounting for new and innovative effective biorational larvicides, due to the development of resistance to some currently utilized mosquito larvicides, undesirable non-target effects, and US Environmental Protection Agency (EPA) restrictions. Methionine is a human nutrient essential amino acid that unexpectedly has been shown to be a valuable safe pest management tool against select insect pests that possess alkaline gut physiology. The present study evaluated larvicidal toxicity of methionine in several pestiferous mosquito (Diptera: Culicidae) genera. Results Concentration-dependent DL-methionine kinetics assays of survival and pupation were conducted in larvae of Aedes albopictus Skuse, Anopheles quadrimaculatus Say, and Culex tarsalis Coquillett in glass jars. High concentrations of DL-methionine yielded 100% mortality for all test species and prevented pupation at a rate equivalent to Bacillus thuringiensis israelensis (Bti) treatments. Concentration kinetics indicated that An. quadrimaculatus was 10-fold more sensitive to DL-methionine than Ae. albopictus and Cx. tarsalis. Conclusions EPA regulations currently exempt methionine in pesticide formulations applied to agricultural crops. This study demonstrates that methionine is a highly effective mosquito larvicide that can provide a beneficial new biorational, environmentally sustainable tool to control pestiferous mosquitoes. © 2018 Society of Chemical Industry.

Methionine is an essential/indispensible amino acid nutrient required by adult and larval honey bees (Apis mellifera L. [Hymenoptera: Apidae]). Bees are unable to rear broods on pollen deficient in methionine, and reportedly behaviorally avoid collecting pollen or nectar from florets deficient in methioinine. In contrast, it has been demonstrated that methionine is toxic to certain pest insects; thus it has been proposed as an effective biopesticide. As an ecofriendly integrated pest management agent, methionine boasts a novel mode of action differentiating it from conventional pesticides, while providing non-target safety. Pesticides that minimize collateral effects on bees are desirable, given the economic and ecological concerns about honey bee health. The aim of the present study was to assess the potential impact of the biopesticide methionine on non-target adult and larval honey bees. Acute contact adult toxicology bioassays, oral adult assessments and chronic larval toxicity assessments were performed as per U.S. Environmental Protection Agency (EPA) requirements. Our results demonstrated that methionine fits the U.S. EPA category of practically nontoxic (i.e. lethal dose to 50% mortality or LD50 > 11µg/bee) to adult honey bees. The contact LD50 was > 25µg/bee and the oral LD50 was > 100µg/bee. Mortality was observed in larval bees that ingested DL-methionine (effective concentration to 50% mortality or EC50 560µg/bee). Therefore, we conclude that methionine poses little threat to the health of the honey bee, due to unlikely exposure at concentrations shown to elicit toxic effects.

The push for sustainable intensification requires development of alternative strategies for managing crop production that improve yields while maintaining or enhancing environmental services. We propose that intraspecific mixtures potentially exploit landscape ecosystem services to help suppress pests, impede disease spread, and ultimately improve yields. To test this hypothesis, we conducted a three-year field study of wheat cultivar mixtures compared to sole cultivar stands and evaluated pest control, yield, and economic benefits. Arthropod pests were not abundant in our experiment and predator abundance varied unpredictably across mixtures and sole cultivar stands. We found that mixtures suppressed foliar diseases at a level comparable to that of a fungicide application but had less impact on head diseases. Yield and economic return over variable costs were similar for mixtures and sole cultivar stands (3875 vs 3817 Mg ha−1 of wheat, $473 vs $462 ha−1, respectively), indicating that mixtures may provide similar yields and economic returns. In the three years of this project, there was no substantial benefit of using mixtures, but neither was there a penalty, indicating that planting mixtures can minimize risks should insect pests or disease outbreak.

The hydrilla tip mining midge, Cricotopus lebetis Sublette (Diptera: Chironomidae), is a biological control agent of the invasive aquatic weed hydrilla, Hydrilla verticillata (L.f.) Royle (Hydrocharitaceae). Mass rearing of the midge for augmentative releases can be compromised by competition from the adventive hydrilla leafcutter moth, Parapoynx diminutalis Snellen (Lepidoptera: Crambidae). The objective of this study was to evaluate the biorational pesticide Bacillus thuringiensis (subspecies kurstaki) (Btk) for reducing competition by the moth in laboratory colonies of the hydrilla tip mining midge. Dose response bioassays with Btk were completed with both species to determine the minimum concentration that kills the moth without affecting midge production. Adult moth emergence was significantly reduced at concentrations of 2.0 mL Btk per 3.8 L of well water. A concentration of 0.2 mL Btk per 3.8 L of well water also reduced the number of emerging moths by 50%. However, midge development declined, although not significantly at the higher 2.0 mL Btk concentration compared with the control. Therefore, concentrations of 0.2 or 2.0 mL Btk per 3.8 L of well water would be appropriate for controlling competition by P. diminutalis in C. lebetis colonies. The lower concentration (0.2 mL Btk) would be appropriate for maintenance control due to its minimal impact on the midge. However, a severe infestation of P. diminutalis might justify the higher concentration of 2.0 mL Btk for maximum impact on the moth. Implementing selective pest management strategies in a biological control agent colony can help increase production and improve the quality of the insects. ResumenEl jejen minador de la punta de hidrilla, Cricotopus lebetis Sublette (Diptera: Chironomidae), es un agente de control biologico de la maleza hidrilla acuatica invasora, Hydrilla verticillata (L.f.) Royle (Hydrocharitaceae). La cria en masa del jejen para la liberacion aumentativa puede estar comprometida por la competencia con la polilla cortadora de hoja de hidrilla adventiva, Parapoynx diminutalis Snellen (Lepidoptera: Crambidae). El objetivo de este estudio fue evaluar el pesticida biorracional Bacillus thuringiensis (subespecie kurstaki) (Btk) para reducir la competencia por la polilla en las colonias de laboratorio del jejen minador de la punta de hidrilla. Se hicieron bioensayos de la respuesta a la dosis de Btk con las dos especies para determinar la concentracion minima que mata a la polilla sin afectar la produccion del jejen. La emergencia de los adultos de la polilla se redujo significativamente a concentraciones de 2,0 ml Btk por 3,8 L de agua de pozo. Una concentracion de 0,2 ml Btk por 3,8 L de agua de pozo tambien redujo el numero de polillas emergentes en un 50%. Sin embargo, el desarrollo del jejen se redujo, aunque no de forma significativa en la mayor concentracion de 2,0 ml de Btk en comparacion con el control. Por lo tanto, las concentraciones de 0,2 o 2,0 ml Btk por 3,8 L de agua asi serian apropiadas para el manejo de la competencia por P. diminutalis en colonias de C. lebetis. La concentracion mas baja (0,2 ml Btk) seria apropiada para el mantenimiento del control debido a su impacto minimo sobre el jejen. Sin embargo, una infestacion severa de P. diminutalis podria justificar la mayor concentracion de 2,0 ml Btk para el maximo impacto sobre la polilla. La aplicacion de estrategias de manejo de plagas selectivas en una colonia agente de control biologico puede ayudar a aumentar la produccion y mejorar la calidad de los insectos. View this article in BioOne

This investigation documents the expression of the in vivo dimorphic program exhibited by the insect mycopathogen Metarhizium rileyi. This insect mycopathogen represents the key mortality factor regulating various caterpillar populations in legumes, including subtropical and tropical soybeans. Using two hosts and M. rileyi isolates, we have measured M. rileyi growth rates under in vivo and in vitro conditions and have assessed the pathogen’s impact on host fitness. Significantly, the hyphal bodies-to-mycelia transition that occurs at the late infection stage is regulated by a quorum-sensing molecule(s) (QSM) that triggers hyphal bodies (Hb) to synchronously switch to the tissue-invasive mycelia. Within hours of this transition, the host insect succumbs to mycosis. The production of the QS chemical(s) occurs when a quorum of Hb is produced in the hemolymph (late-stage infection). Furthermore, the QS activity detected in late-stage infected sera is unique and is unrelated to any known fungal QSM. The lack of similar QS activity from conditioned media of M. rileyi suggests that the chemical signal(s) that mediates the dimorphic switch is produced by host tissues in response to a quorum of hyphal bodies produced in the host hemolymph. The serum-based QS activity is retained after lyophilization, mild heat treatment, and proteinase digestion. However, attempts to extract/identify the QSM have been unsuccessful. Results suggest that the observed hyphal body-to-mycelia transition is a multi-step process involving more than one chemical signal.

Cricotopus lebetis Sublette (Diptera: Chironomidae) is an aquatic insect adventive in Florida. Evidence from previous studies suggest the insect may have value as an augmentative biological control agent for hydrilla, Hydrilla verticillata (L.f.) Royle (Hydrocharitaceae), but there are gaps in knowledge of the biology and life history traits. To increase understanding of this insect, this study was comprised of 3 experiments. In the first experiment, we investigated the productivity and survival rate of C. lebetis across 6 generations by analyzing our colony data. Then the effect of intraspecific competition on the rates of pupal and adult eclosion was studied by monitoring hydrilla tips in test tubes with varying numbers of larvae. Finally, the level of hydrilla stem tip damage caused by a C. lebetis larva was determined by monitoring tip damage following feeding of a known number of larvae on a standardized number of hydrilla tips. The first experiment revealed the average survival rate of C. lebetis from egg to adult was 16.4%. Approximately a third of the females (30.2%) oviposited. The egg masses had an average of 154.5 eggs per egg mass and an 83.7% fertility rate. Investigation of intraspecific competition revealed pupation and adult eclosion was highest with 1 C. lebetis larva per hydrilla stem tip. Evaluation of the impact of C. lebetis larvae feeding on hydrilla showed stem tips in treatments with C. lebetis larvae experienced 38% higher damage compared to stem tips in control treatments. Overall, this study provided valuable information useful in improving the mass rearing of C. lebetis and predicting the damage caused by C. lebetis. For example, for efficient mass rearing, an average of 1 larva per hydrilla tip should be maintained with the remainder of eggs being used for augmentative releases.

Mosquito larvicides provide a source-reduction strategy to diminish adult females that bite and potentially spread pathogens. Demands are mounting for new and innovative effective biorational larvicides, due to the development of resistance to some currently utilized mosquito larvicides, undesirable non-target effects, and US Environmental Protection Agency (EPA) restrictions. Methionine is a human nutrient essential amino acid that unexpectedly has been shown to be a valuable safe pest management tool against select insect pests that possess alkaline gut physiology. The present study evaluated larvicidal toxicity of methionine in several pestiferous mosquito (Diptera: Culicidae) genera.Concentration-dependent DL-methionine kinetics assays of survival and pupation were conducted in larvae of Aedes albopictus Skuse, Anopheles quadrimaculatus Say, and Culex tarsalis Coquillett in glass jars. High concentrations of DL-methionine yielded 100% mortality for all test species and prevented pupation at a rate equivalent to Bacillus thuringiensis israelensis (Bti) treatments. Concentration kinetics indicated that An. quadrimaculatus was 10-fold more sensitive to DL-methionine than Ae. albopictus and Cx. tarsalis.EPA regulations currently exempt methionine in pesticide formulations applied to agricultural crops. This study demonstrates that methionine is a highly effective mosquito larvicide that can provide a beneficial new biorational, environmentally sustainable tool to control pestiferous mosquitoes. © 2018 Society of Chemical Industry.

House flies (Musca domestica L.) throughout the world are infected with the salivary gland hypertrophy virus MdSGHV (Hytrosaviridae). Although the primary route of infection is thought to be via ingestion, flies that are old enough to feed normally are resistant to infection per os, suggesting that the peritrophic matrix (PM) is a barrier to virus transmission. Histological examination of the peritrophic matrix of healthy flies revealed a multilaminate structure produced by midgut cells located near the proventriculus. SEM revealed the PM to form a confluent sheet surrounding the food bolus with pores/openings less than 10 nm in diameter. TEM revealed the PM to be multilayered, varying in width from 350 to 900 nm, and generally thinner in male than in female flies. When flies were fed on the reducing agents dithiothetriol (DTT) or tris (2-caboxyethyl)phosphine hydrochloride (TCEP) for 48 h before per os exposure to the virus, infection rates increased 10- to 20-fold compared with flies that did not receive the reducing agent treatments. PM’s from flies treated with DTT and TCEP displayed varying degrees of disruption, particularly in the outer layer, and lacked the electron-dense inner layer facing the ectoperitrophic space. Both drugs were somewhat toxic to the flies, resulting in > 40% mortality at doses greater than 10 mM (DTT) or 5 mM (TCEP). DTT increased male fly susceptibility (55.1% infected) more than that of females (7.8%), whereas TCEP increased susceptibility of females (42.9%) more than that of males (26.2%). The cause for the sex differences in response to oral exposure the reducing agents is unclear. Exposing flies to food treated with virus and the reducing agents at the same time, rather than pretreating flies with the drugs, had no effect on susceptibility to the virus. Presumably, the reducing agent disrupted the enveloped virus and acted as a viricidal agent. In summary, it is proposed that the reducing agents influence integrity of the PM barrier and increase the susceptibility of flies to infection by MdSGHV.