Contradictions in host plant resistance to pests: spider mite (Tetranychus urticae Koch) behaviour undermines the potential resistance of smooth‐leaved cotton (Gossypium hirsutum L.)

Abstract

Paradoxically, the relative inhospitality of glabrous leaves may have induced mites to concentrate in protected leaf sections, causing more localised and more severe damage, negating the yield benefits from fewer mites. These results highlight interactions between leaf microenvironment, pest behaviour and plant productivity that may have implications for other instances of plant resistance.

In situ visualization of spider mite-plant interfaces

“…In contrast, smooth-leaved cotton plants were occupied with fewer mites than pubescent ones (Reddall et al, 2011). However, in the present study T. urticae attached successfully to wettable and non-wettable plant surfaces as well as to hairy, glandular hairy, crystalline waxy, and non-structured ( smooth') plant surfaces (Figs.…”

“…Pubescent plant species and cultivars have repeatedly been reported to prevent attacks of spider mites and impact their fitness (e.g., Rasmy, 1985;Luczynski, 1988;Nihoul, 1993;Walter, 1996;Grazzini et al, 1997;Fernández-Muñoz et al, 2003;Reddall et al, 2011;Torre Figueiredo et al, 2013). The effect of host plants on spider mites has been previously assumed to cause morphological changes of tarsal bristles on the forelegs (Fritzsche, 1964).…”

Fitness of twospotted spider mites is more affected by constitutive than induced resistance traits in cotton (Gossypiumspp.)

“…Leaf hairiness was assessed by counting the number of leaf hairs on an 8 mm diameter leaf disc taken from 10 leaves of each genotype from field (Experiment 1) and glasshouse (Experiment 2) under a binocular microscope. 26 As trichomes have between one and five individual hairs, each type of trichome was counted separately and the total number of hairs multiplied by the number of hairs held on each trichome. It is possible that at high hair density the distance between hairs is less than the body width of a mite and could impair movement and feeding.…”

“…These represent an up‐front cost to the plant whether the pest is present or not. In cotton, constitutive morphological traits such as okra leaf shape and smooth leaf have been associated with slower mite population development . Terpenoids (e.g.…”

“…In cotton, constitutive morphological traits such as okra leaf shape and smooth leaf have been associated with slower mite population development. 25,26 Terpenoids (e.g. gossypol) and flavonoids (e.g.…”