Trichome-based host plant resistance of lycopersicon species and the biocontrol agent Mallada signata: are they compatible?

Trichome-based host plant resistance of Lycopersicon (Solanaceae) species offers the potential to reduce pesticide use in tomato production, but its compatibility with biocontrol agents is largely unknown. The effect of trichome-based host plant resistance on the lacewing biocontrol agent, Mallada signata, was assessed for five accessions of L. cheesmanii, four accessions of Lycopersicon hirsuturn, two accessions of Lycopersicon pennellii, and one Lycopersicon esculenturn cultivar. An intact leaf was isolated from the whole plant using Tangletrap to coat the petiole and 20 green peach aphids [Myzus persicae (Sulzer) (Homoptera: Aphididae)] were placed on the leaf surface. After 24 h, 10 lacewings were placed on the leaf. The numbers of dead, trapped by exudates, untrapped and predated lacewings and aphids, and the numbers that had left the leaf were recorded a further 24 h later. Differences in insect designations between accessions were analysed using ANOVA. A General Linear Model (GLM), consisting of the densities of each trichome type and leaf area, was fitted to the data to determine the role of trichomes on the observed effects on lacewings and aphids. Lace-wing mortality was greater on one accession of L. pennellii and one accession of L. hirsutum than on L. esculenturn. The GLM indicated that type IV trichomes decreased the numbers of aphids predated, and increased cannibalism and, along with type III trichomes, increased entrapment-related predator mortality. Although there were no differences in the numbers of predated aphids, with the majority predated for all accessions, the compatibility of trichome-based host plant resistance of Lycopersicon species and the biocontrol of aphids by lacewings is questionable.