Do plant trichomes cause more harm than good to predatory insects?

Authors: Riddick, Eric; Simmons, Alvin

Submitted to: Pest Management Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/23/2014
Publication Date: 10/16/2014
Publication URL: http://handle.nal.usda.gov/10113/60844
Citation: Riddick, E.W., Simmons, A.M. 2014. Do plant trichomes cause more harm than good to predatory insects? Pest Management Science. 70:1655-1665. doi: 10.1002/ps.3772.

Interpretive Summary: Some plants use epidermal hairs (trichomes) on leaves and stems to discourage plant-feeding pests from attacking them. The effects of plant trichomes on predatory insects and mites are equivocal. We conducted a comprehensive review of the scientific literature to determine if plant trichomes have harmful, neutral or beneficial effects on predators. Many predators play an essential role in biological control of plant pests. Our results reveal that plant trichomes cause more harmful than beneficial effects on predators. Harmful effects include decreasing movement, extending development time, reducing oviposition rate and predation potential. In some instances, glandular and non-glandular trichomes entrap predators, resulting in their death from starvation or desiccation. When developing and testing cultivars with increased resistance to plant pests, we should determine if these technologies are compatible with predators.

Technical Abstract: Plants may use epidermal hairs (trichomes) as a morphological defense against attacks from some herbivores. Predatory arthropods can serve plants as biocontrol agents against herbivores. Whether or not plant trichomes work in concert with predators is equivocal. We reviewed the scientific literature to test the assertion that trichome-bearing (pubescent) plants have neutral or no harmful effects on predators, and therefore, do not reduce their predation potential. The USDA, Digital Desktop (DigiTop), National Agricultural Library system of research databases facilitated this study. We found 63 published records detailing interactions between plant trichomes and predators. Our results indicate that plant trichomes have more harmful than beneficial effects on the life history of predators. Glandular and non-glandular trichomes can impede or inhibit mobility of predators, resulting in reduced searching and predation of herbivores on plants. In worst cases, predators do not escape from entrapment in glandular exudates, or on hooked tips of non-glandular trichomes; they eventually die from desiccation or starvation. Plants with high trichome density (with or without associated glands) appear to cause the most harm to predators foraging for prey. Fortunately, most harmful effects are not lethal; they usually affect movement, development, oviposition and predation potential. When developing and testing cultivars with increased resistance to herbivory, we should determine if these technologies are compatible with the life history of predators.