Movement and host finding of Trichogramma brassicae on maize plants
Suverkropp, B.P. ; Bigler, F. ; Lenteren, J.C. van - \ 2010
Bulletin of Insectology 63 (2010)1. - ISSN 1721-8861 - p. 115 - 127.
european corn-borer - ostrinia-nubilalis - egg parasitoids - hymenoptera trichogrammatidae - entomophagous insects - bezdenko hymenoptera - evanescens westwood - searching behavior - mamestra-brassicae - biological-control
Direct observation of searching patterns and residence times of Trichogramma brassicae Bezdenko on maize plants were made at 18 degrees C and 25 degrees C. Temperature had a strong effect on the residence times: parasitoids spent an average of 44.9 minutes on the plant at 18 degrees C and 20.8 minutes at 25 degrees C. Observations on single plants showed that parasitoids mainly walked from one leaf to another. The leaf part closest to the stem was the most often visited and longest searched leaf area. At 18 degrees C, many parasitoids went to the lower leaf side and stopped searching. Leaf level, leaf side or size of the leaf where the parasitoid landed had no effect on residence time. Although about 20% of total searching time was spent in following the leaf edge and mid rib, Ostrinia (Hubner) egg masses touching the mid rib were not found more often than those away from the mid rib. Host finding was also not influenced by the position of egg masses relative to the stem, or by the leaf height. Naturally laid egg masses were found twice as often as artificially placed egg masses. The scales that O. nubilalis adults left in small patches on the plant seemed to be as effective a cue as host cues artificially confined to a small area around the host egg mass. When maize plants were covered with fine netting and a number of O. nubilalis kept close to the plant for one night in such a way that the moths were unable to touch the plants, host finding and residence times of T. brassicae were significantly higher on these plants than on untreated plants. This indicates that volatile cues left by O. nubilalis had an arresting effect and were used in host finding by T. brassicae.
The response specificity of Trichogramma egg parasitoids towards infochemicals during host location
Fatouros, N.E. ; Bukovinszkine-Kiss, G. ; Dicke, M. ; Hilker, M. - \ 2007
Journal of Insect Behavior 20 (2007)1. - ISSN 0892-7553 - p. 53 - 65.
pieris-brassicae l - evanescens westwood - behavioral variations - mamestra-brassicae - biological-control - strains - hymenoptera - oviposition - lepidoptera - kairomones
Parasitoids are confronted with many different infochemicals of their hosts and food plants during host selection. Here, we investigated the effect of kairomones from the adult host Pieris brassicae and of cues present on Brussels sprout plants infested by P. brassicae eggs on the behavioral response of the egg parasitoid Trichogramma evanescens. Additionally, we tested whether the parasitoid¿s acceptance of P. brassicae eggs changes with different host ages. The wasps did not discriminate between olfactory cues from mated and virgin females or between mated females and males of P. brassicae. T. evanescens randomly climbed on the butterflies, showing a phoretic behavior without any preference for a certain sex. The parasitoid was arrested on leaf parts next to 1-day-old host egg masses. This arrestment might be due to cues deposited during oviposition. The wasps parasitized host eggs up to 3 days old equally well. Our results were compared with former studies on responses by T .brassicae showing that T. evanescens makes less use of infochemicals from P. brassicae than T. brassicae.