The effects of alternative host plant species and plant quality on Dicyphus hesperus populations

•Dicyphus hesperus populations may be affected by plant species and nitrogen content.•Three alternative host plants were paired nitrogen-manipulated tomato plants.•Greater omnivore emergence and population growth occurred in mullein arenas.•Tomato plant nitrogen content only affected D. hesperus in mullein arenas.•Mullein is a superior banker plant, followed by eggplant and finally, pepper.

Biological control can be used to defend important crops against insect pests, including those that are insecticide resistant. Dicyphus hesperus Knight (Hemiptera: Miridae) is a generalist zoophytophagous predator and biological control agent of Trialeurodes vaporariorum (Westwood) (Hemiptera: Aleyrodidae), the greenhouse whitefly. Because D. hesperus is an omnivore, the structure of the plant community and the nutritional value of the plants in the release habitat are likely to affect its establishment and population growth. Fifteen adult D. hesperus (ten females, five males) were placed into arenas that contained a tomato plant (Solanum lycopersicum L., Solanales: Solanaceae) of either high or low leaf nitrogen content and one of three alternative host plants: mullein (Verbascum thapsus L., Lamiales: Scrophulariaceae), pepper (Capiscum annuum L., Solanales: Solanaceae), or eggplant (Solanum melongena L., Solanales: Solanaceae). Adults remained in the enclosures for seven days; following their removal, F1 generation nymphs, and subsequently, F1 adults were counted as they emerged and the percent change in population size between generations was calculated. Nymph emergence was affected by the alternative host plant, such that emergence was greatest in arenas with mullein. Tomato nitrogen content only affected nymph emergence in arenas with mullein; more nymphs emerged when low nitrogen tomato was present. The presence of mullein also resulted in larger F1 adult numbers and a greater change in population size between generations compared to eggplant and pepper. Our results indicate that growing tomato and mullein together, regardless of tomato plant nitrogen content, is beneficial to D. hesperus populations.