Bioturbation by endogeic earthworms facilitates entomopathogenic nematode movement toward herbivore-damaged maize roots

Entomopathogenic nematodes (EPNs) have been extensively studied as potential biological control agents against root-feeding crop pests. Maize roots under rootworm attack have been shown to release volatile organic compounds, such as (E)-β-caryophyllene (Eβc) that guide EPNs toward the damaging larvae. As yet, it is unknown how belowground ecosystems engineers, such as earthworms, affect the biological control capacity of EPNs by altering the root Eβc-mediated tritrophic interactions. We here asked whether and how, the presence of endogeic earthworms affects the ability of EPNs to find root-feeding larvae of the beetle Diabrotica balteata. First, we performed a field mesocosm experiment with two diverse cropping systems, and revealed that the presence of earthworms increased the EPN infection potential of larvae near maize roots. Subsequently, using climate-controlled, olfactometer-based bioassays, we confirmed that EPNs response to Eβc alone (released from dispensers) was two-fold higher in earthworm-worked soil than in earthworm-free soil. Together our results indicate that endogeic earthworms, through burrowing and casting activities, not only change soil properties in a way that improves soil fertility but may also enhance the biocontrol potential of EPNs against root feeding pests. For an ecologically-sound pest reduction in crop fields, we advocate agricultural practices that favour earthworm community structure and diversity.

Encapsulated Entomopathogenic Nematodes Can Protect Maize Plants from Diabrotica balteata Larvae

To face the environmental problems caused by chemical pesticides, more ecologically friendly alternative pest control strategies are needed. Entomopathogenic nematodes (EPN) have great potential to control soil-dwelling insects that cause critical damage to the roots of cultivated plants. EPN are normally suspended in water and then sprayed on plants or onto the soil, but the inconsistent efficiency of this application method has led to the development of new formulations. Among them is the use of alginate capsules or beads that encapsulate the EPN in favorable conditions for later application. In this study, we evaluated whether alginate beads containing EPN are able to kill larvae of the banded cumber beetle Diabrotica balteata LeConte and thereby protect maize plants from damage by these generalist rootworms. EPN formulated in beads were as effective as sprayed EPN at killing D. balteata. They were found to protect maize plants from D. balteata damage, but only if applied in time. The treatment failed when rootworm attack started a week before the EPN beads were applied. Hence, the well-timed application of EPN-containing alginate beads may be an effective way to control root herbivores.

Efecto de bioplaguicidas sobre la incidencia de plagas y enfermedades foliares y componentes de rendimiento del frijol común (Phaseolus vulgaris L.) en Santa Rosa de Copán

El daño causado por plagas y enfermedades es uno de los principales factores que afectan la producción a nivel nacional del frijol (P. vulgaris) ya que atacan todos los órganos y etapas de crecimiento, producción y almacén. Con objetivo de evaluar el efecto de bioplaguicidas sobre la incidencia de plagas y enfermedades foliares en frijol común (P. vulgaris) en Santa Rosa de Copán durante la campaña de enero-abril de 2017, se realizaron dos ensayos. El primero consistió en evaluar el control de los bioplaguicidas sobre la incidencia de plagas; y en el segundo se valoró la incidencia y severidad de enfermedades foliares, ambos casos se contrastaron bioplaguicidas con un testigo químico y uno absoluto, la aplicación de los mismos se realizó en las fases V4 (vegetativa) y R5 (regenerativa, prefloración). Las variables consideradas estuvieron encaminadas a evaluar las plagas, las enfermedades más comunes que aparecieron en campo, y las variables de rendimiento. Los resultados reflejaron diferencia estadística significativa con respecto a P_0.05, donde las plagas con mayor frecuencia fueron Salta hojas (Empoasca kraemeri), Mosca blanca (Bemishia tabaci), Diabróticas (Diabrotica balteata), a la vez se registró presencia de controladores biológicos como fue Orius insidosus; las enfermedades con mayor presencia fueron Mancha angular (Phaseoisariopsis griseola) y Roya (Uromyces appendiculatus). En las variables de rendimiento se encontró diferencia estadística significativa con respecto al testigo absoluto. En base a los resultados obtenidos en ambos ensayos se recomienda usar Engeo 24.7 SC a 1L.ha-1 y Amistar xtra 28 SC a misma dosis de forma preventiva.

Striped Cucumber Beetle Acalymma vittatum F. (Insecta: Coleoptera: Chrysomelidae)

The striped cucumber beetle, Acalymma vittatum F. (Figure 1) is a serious agricultural pest of plants in the family Cucurbitaceae in eastern North America. Crops affected by larval and adult feeding include cucumber, Cucumis sativus L., cantaloupe, Cucumis melo L., pumpkin, Cucurbita pepo L., and other Cucurbita spp. (Dill and Kirby 2016). The striped cucumber beetle is a vector of the plant disease bacterial wilt (Eaton 2016). Though the striped cucumber beetle occurs throughout Florida, it is the least commonly reported among three chrysomelid species on cucurbit crops in the state. The spotted cucumber beetle, Diabrotica undecimpunctata howardi Barber, and banded cucumber beetle, Diabrotica balteata LeConte, are more common in Florida, causing damage symptoms that are similar to striped cucumber feeding damage (Webb 2010). Includes: Introduction - Distribution - Description and Life Cycle - Damage - Monitoring - Management - Selected References.https://edis.ifas.ufl.edu/in1215 Also published at http://entnemdept.ufl.edu/creatures/VEG/BEAN/striped_cucumber_beetle.html

Synthesis of (6R,12R)-6,12-Dimethylpentadecan-2-one, the Female-Produced Sex Pheromone from Banded Cucumber Beetle Diabrotica balteata, Based on a Chiron Approach

Herein we describe a synthesis of (6 R,12 R)-6,12-dimethylpentadecan-2-one (5), the female produced sex pheromone of banded cucumber beetle Diabrotica balteata Le Conte, from ( R)-4-methyl-δ-valerolactone, a methyl-branched chiron.

Diabrotica balteata. [Distribution map].

A new distribution map is provided for Diabrotica balteata (LeConte). Coleoptera: Chrysomelidae. Hosts: polyphagous. Information is given on the geographical distribution in North America (Mexico, USA, Alabama, Arizona, Arkansas, California, Florida, Georgia, Louisiana, Mississippi, New Mexico, North Carolina, South Carolina, Texas), Central America and Caribbean (Belize, Costa Rica, Cuba, El Salvador, Guatemala, Honduras, Nicaragua, Panama), South America (Colombia, Venezuela).

ADULT AND LARVAL BIOASSAYS FOR DETERMINING RESISTANCE OF SWEETPOTATO GENOTYPES TO Diabrotica SPP.

Production of sweetpotatoes is severely limited by several insect pests, and new pest management approaches for this crop are needed. A host plant resistance research program typically depends on reliable bioassay procedures to streamline evaluation of germplasm. Thus, bioassay procedures were developed for both adults and larvae of two cucumber beetle species (Diabrotica balteata and D. undecimpunctata). For the adult bioassay, a piece of sweetpotato peel (periderm & cortex with stele removed) was embedded periderm-side up in plaster in a Petri dish, and a single adult was placed on it. Plugs were changed as needed and adult longevity was measured. A laboratory bioassay also was developed for Diabrotica larvae. Plugs (0.9 cm diameter) of sweetpotato peel or stele were placed periderm-side up into sterile microcentrifuge tubes (1.5 mL) containing 0.5 mL water-agar to prevent desiccation. One second instar Diabrotica was added to each micro centrifuge tube, which was held at 25 °C for 12 days. Surviving larvae were weighed. Diabrotica larvae grew larger when they were fed stele than when they were fed peels of any sweetpotato genotype. Larval growth was not different among genotypes for any of the stele treatments. However, larval growth on the peel of the resistant genotypes (Regal and W-375) was significantly lower than for the susceptible cultivars Beauregard or SC1149-19. These bioassays were consistent with field results, indicating that these techniques could be useful for evaluating pest resistance in sweetpotato genotypes for Diabrotica and other insect species.