ORCID Profile
0000-0001-8067-4416
Current Organisation
USDA Agricultural Research Service
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Publisher: Springer Science and Business Media LLC
Date: 26-02-2021
DOI: 10.1007/S10340-021-01349-4
Abstract: Entomopathogenic nematodes (EPN) have great potential as biological control agents against root-feeding insects. They have a rapid and long-lasting mode of action, minimal adverse effects on the environment and can be readily mass-produced. However, they have a relatively short shelf-life and are susceptible to desiccation and UV light. These shortcomings may be overcome by encapsulating EPN in Ca 2+ -alginate hydrogels, which have been shown to provide a humid and UV protective shelter. Yet, current Ca 2+ -alginate formulations do not keep EPN vigorous and infectious for a prolonged period of time and do not allow for their controlled release upon application. Here, we introduce solid Ca 2+ -alginate beads which we supplemented with glycerol to better retain the EPN during storage and to ensure a steady release when applied in soil. Glycerol-induced metabolic arrest in EPN ( Heterorhabditis bacteriophora ) resulting in quiescence and total retainment of EPN when added to beads made with 0.5% sodium alginate and 2% CaCl 2 ·2H 2 O solutions. More than 4,000 EPN could be embedded in a single 4–5-mm diameter bead, and quiescence could be broken by adding water, after which the EPN readily emerged from the beads. In a field trial, the EPN beads were as effective in reducing root damage by the western corn rootworm (WCR, Diabrotica virgifera virgifera ) as EPN that were applied in water. Although further improvements are desirable, we conclude that Ca 2+ -alginate beads can provide an effective and practical way to apply EPN for the control of WCR larvae.
Publisher: Springer Science and Business Media LLC
Date: 02-06-2016
Publisher: Elsevier BV
Date: 10-2014
DOI: 10.1016/J.JIP.2014.08.002
Abstract: As obligate parasites, entomopathogenic nematodes (EPN) rely on insect hosts to complete their development. In insect pest management, EPN infectiousness has varied a lot. A better understanding of their host-finding behavior in the rhizosphere is therefore crucial to enhance EPN potential in biological control. As previously demonstrated, roots can be used as a pathway to insect hosts by EPN, but this interaction and its impact on EPN foraging remain poorly documented. Three artificial model-roots with different degrees of complexity and connectivity were designed to investigate the impact of root architecture on foraging behavior of the EPN Heterorhabditis megidis. Insect baits were placed at the bottom of each model-root that was subsequently buried in moist sand. After injection of the EPN, the number of EPN-infected baits as well as the number of mature nematodes inside each in idual carcass was recorded. The influence of insect-induced root volatiles was also evaluated by spiking the baits with a synthetic version of a natural insect-induced root cue. The ecological relevance of the results was tested in soil with two maize genotypes each exhibiting broadly different root architectures. H. megidi performed better in presence of model-roots. Foraging performances of H. megidis declined with the increasing model-root complexity. Adding the synthetic root volatile dramatically changed this pattern and favored the EPN on the most complex model-roots. H. megidis also moved in the vicinity of maize roots to find the insect baits in soil, and natural root architecture also tended to shape H. megidis foraging behavior. This study adds to the scarce body of literature characterizing physical and chemical interactions between EPN and roots. The present data illustrate that root architecture not only modifies plant quality but also shapes upper trophic levels' ecology.
Publisher: Elsevier
Date: 2013
Publisher: Wiley
Date: 21-02-2013
DOI: 10.1111/PBI.12053
Abstract: Genetic manipulation of plant volatile emissions is a promising tool to enhance plant defences against herbivores. However, the potential costs associated with the manipulation of specific volatile synthase genes are unknown. Therefore, we investigated the physiological and ecological effects of transforming a maize line with a terpene synthase gene in field and laboratory assays, both above- and below ground. The transformation, which resulted in the constitutive emission of (E)-β-caryophyllene and α-humulene, was found to compromise seed germination, plant growth and yield. These physiological costs provide a possible explanation for the inducibility of an (E)-β-caryophyllene-synthase gene in wild and cultivated maize. The overexpression of the terpene synthase gene did not impair plant resistance nor volatile emission. However, constitutive terpenoid emission increased plant apparency to herbivores, including adults and larvae of the above ground pest Spodoptera frugiperda, resulting in an increase in leaf damage. Although terpenoid overproducing lines were also attractive to the specialist root herbivore Diabrotica virgifera virgifera below ground, they did not suffer more root damage in the field, possibly because of the enhanced attraction of entomopathogenic nematodes. Furthermore, fewer adults of the root herbivore Diabrotica undecimpunctata howardii were found to emerge near plants that emitted (E)-β-caryophyllene and α-humulene. Yet, overall, under the given field conditions, the costs of constitutive volatile production overshadowed its benefits. This study highlights the need for a thorough assessment of the physiological and ecological consequences of genetically engineering plant signals in the field to determine the potential of this approach for sustainable pest management strategies.
Publisher: Proceedings of the National Academy of Sciences
Date: 11-08-2009
Abstract: When attacked by herbivorous insects, plants emit volatile compounds that attract natural enemies of the insects. It has been proposed that these volatile signals can be manipulated to improve crop protection. Here, we demonstrate the full potential of this strategy by restoring the emission of a specific belowground signal emitted by insect-damaged maize roots. The western corn rootworm induces the roots of many maize varieties to emit ( E )-β-caryophyllene, which attracts entomopathogenic nematodes that infect and kill the voracious root pest. However, most North American maize varieties have lost the ability to emit ( E )-β-caryophyllene and may therefore receive little protection from the nematodes. To restore the signal, a nonemitting maize line was transformed with a ( E )-β-caryophyllene synthase gene from oregano, resulting in constitutive emissions of this sesquiterpene. In rootworm-infested field plots in which nematodes were released, the ( E )-β-caryophyllene-emitting plants suffered significantly less root damage and had 60% fewer adult beetles emerge than untransformed, nonemitting lines. This demonstration that plant volatile emissions can be manipulated to enhance the effectiveness of biological control agents opens the way for novel and ecologically sound strategies to fight a variety of insect pests.
Publisher: Springer Science and Business Media LLC
Date: 05-05-2012
Publisher: ACM
Date: 26-10-2008
Publisher: Oxford University Press (OUP)
Date: 06-2014
DOI: 10.1603/EN13248
Location: United States of America
No related grants have been discovered for Bruce Hibbard.