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Providing evidence to improve practice

Individual study: Response of Trichogramma pretiosum females to extracts of two plants attacked by Heliothis zea

Published source details

Nordlund D.A., Chalfant R.B. & Lewis W.J. (1985) Response of Trichogramma pretiosum females to extracts of two plants attacked by Heliothis zea. Agriculture, Ecosystems & Environment, 12, 127-133


This study is summarised as evidence for the intervention(s) shown on the right. The icon shows which synopsis it is relevant to.

Use chemicals to attract natural enemies Natural Pest Control

A replicated, controlled field study (Nordlund et al. 1985) found greater corn earworm Helicoverpa zea parasitism in plots of corn Zea mays treated with tomato Solanum lycopersicum extract (38% eggs parasitised) than in control plots of corn without tomato extract (29%). Eggs were parasitised by the wasp Trichogramma pretiosum. Parasitism was similar in plots of tomato treated with corn extract (53% eggs parasitised) and controls of tomato without corn extract (54%). A greenhouse experiment found the wasp also parasitised more corn earworm eggs in pots of cowpea Vigna unguiculata treated with tomato extract (52-74% eggs parasitised) than in pots treated with corn extract (19-26%) or untreated controls (18-26%). A lab study found similar results by monitoring parasitism in petri dishes containing the extracts. Plant extracts were obtained by grinding fresh leaves. In the field study extracts were sprayed (at 2 g/plot in 10 ml of hexane) on 1 row by 3 m plots. Controls were left unsprayed. Corn and tomato extract treatments were replicated 30 and 40 times, respectively. Corn earworm eggs were placed at 0.3 m intervals, 50 parasitoid wasps were released and eggs were collected after four hours. The greenhouse trial grew cowpea in 28.8-cm pots.