Integrating immunomarking with ecological and behavioural approaches to assess predation of Helicoverpa spp. larvae by wolf spiders in cotton

Authors: RENDON, DALILA - Commonwealth Scientific And Industrial Research Organisation (CSIRO); Hagler, James; TAYLOR, PHILIP - Macquarie University; WHITEHOUSE, MARY - Commonwealth Scientific And Industrial Research Organisation (CSIRO)

Submitted to: Biological Control
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/31/2018
Publication Date: 4/15/2018
Citation: Rendon, D., Hagler, J.R., Taylor, P., Whitehouse, M. 2018. Integrating immunomarking with ecological and behavioural approaches to assess predation of Helicoverpa spp. larvae by wolf spiders in cotton. Biological Control. 122:51-59. https://doi.org/10.1016/j.biocontrol.2018.03.019.
DOI: https://doi.org/10.1016/j.biocontrol.2018.03.019

Interpretive Summary: Wolf spiders are abundant soil-dwelling predators found in cotton fields. They can kill and eat larvae of the cotton bollworm, a cotton pest, that survive foraging on Bt cotton and descend from the plant to pupate in the soil. However, little is known about their ability to find and kill this pest. Australia scientists used a gut content analysis method (protein marking), pioneered by a scientist in Maricopa, AZ, to evaluate wolf spider predation on bollworm larvae in cotton. The study revealed that a single protein marked larva can be detected in a spider’s gut for up to 72 h after feeding. Gut content assays of field-collected spiders showed evidence of protein-marked bollworm remains in the stomachs of 2.1% of the spiders examined. Due to its ease of development, long prey detection ability, and low cost, the protein marking technique is an effective tool for assessing predation of this cotton pest by wolf spiders in an open field setting.

Technical Abstract: Wolf spiders (Araneae: Lycosidae) are abundant soil-dwelling predators found in cotton fields and can contribute important pest management services. These spiders can kill and consume larvae of the cotton bollworm Helicoverpa spp. (Lepidoptera: Noctuidae) that survive foraging on Bt cotton and descend from the plant to pupate in the soil. We assessed a gut content analysis method using Helicoverpa spp. larvae marked with rabbit immunoglobulin G (IgG; “immunomarking”) to determine predation frequency by wolf spiders in a Bt cotton field. A laboratory prey retention study revealed that a single IgG-marked larva can be readily detected in a spider’s gut for up to 72 h after feeding. A field gut content study provided evidence of IgG-marked Helicoverpa spp. predation in 2.1% of field-collected spiders. A capture-mark-recapture survey revealed that wolf spiders had opportunity to encounter IgG-marked larvae released along field edges, but spiders were recaptured at low rates, which likely reflects high spider motility. In enclosed field arenas, three commonly encountered spider species (Tasmanicosa leuckartii, Hogna crispipes, Hogna kuyani) readily killed and ate Helicoverpa spp. larvae. We concluded from these studies that low likelihood of spider encounter with prey, and not prey rejection, is a likely explanation for the low proportion of field-collected spiders testing positive for IgG marked prey remains. One drawback of the immunomarking technique is the incidence of false positive assays. However, due to its ease of development, long prey detection ability, and low cost, the immunomarking technique is an effective tool for assessing predation of mobile prey by wolf spiders in an open field setting.