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

Abstract

Plants use trichomes as a morphological defense against attacks from herbivores. The literature was reviewed to test the hypothesis that trichome-bearing (pubescent) plants do not cause more harm than good to predators. Forty seven records on interactions between plant trichomes and predatory insects were found. Overall, the records reveal that trichomes have more harmful than beneficial effects on predators. Fortunately, most harmful effects are sublethal; they usually affect movement, development, oviposition and predation potential. In worst cases, sticky exudates from glandular trichomes entrap predators. The hooked tips on non-glandular trichomes impale predators. Entrapped and impaled predators often die from desiccation or starvation. Plant cultivars with high (rather than low) trichome density cause the most harm, and trichomes on tomato and some beans often cause more harm than good to predatory beetles, true bugs and lacewings. Whether these harmful effects have a net negative effect on plant fitness is poorly known and ripe for study. When developing and testing cultivars with increased trichome-based resistance to herbivory, the question as to whether these technologies are compatible with the functional role of those predators (single or combined species) capable of suppressing herbivore populations should be considered.

Identification of Conditions for Successful Aphid Control by Ladybirds in Greenhouses

“…A generalized schematic of the positive (+), neutral (o), or negative (--) interactions that could arise between these factors is presented in Figure 1. Prior research conducted primarily in the laboratory and in open field settings suggests that host plant defenses could have negative or neutral effects on aphids as well as ladybirds [41]. Also, aphid density has a positive effect on ladybirds [21,22], but the effect can become negative if prey becomes scarce, resulting in starvation or cannibalism amongst immature ladybirds.…”

Cell Wall Maturation of Arabidopsis Trichomes Is Dependent on Exocyst Subunit EXO70H4 and Involves Callose Deposition

“…Roles in the drought and heat stresses (Ehleringer, 1982;Grammatikopoulos and Manetas, 1994;Espigares and Peco, 1995;Pérez-Estrada et al, 2000) and heavy metal detoxification and deposition (Salt et al, 1995;Pérez-Estrada et al, 2000;Servin et al, 2012;Jr and Kupper, 2014) also have been described. Additionally, different forms of trichomes have been linked to increased plant resistance against herbivores across different species of plants (for review, see Riddick and Simmons, 2014).…”

The effect of flowering calendula and cuphea plants onOrius insidiosussurvival and predation ofAphis glycines

“…When we conducted a second experiment comparing survival of O. insidiosus on A c c e p t e d M a n u s c r i p t glandular and non-glandular cuphea, more dead individuals were removed from locations on the glandular plants than on the non-glandular plants, indicating glandular trichomes can play a significant role in O. insidiosus mortality. Previous research has shown that predators can become entangled by the sticky exudate produced by the heads of glandular trichomes, impeding their search behavior, reducing oviposition rates, and potentially resulting in death from starvation or from toxins in the exudate (Lovinger, Liewehr, & Lamp, 2000;Gassmann & Hare, 2005;Smith, 2005;Riddick & Simmons, 2014). Although sublethal effects from glandular trichomes are common, ours is one of the comparatively few studies to show increased mortality in the presence of glandular trichomes (Riddick & Simmons, 2014).…”