Variation in locomotion between laboratory strains of Trichogramma maidis and its impact on parasitism of eggs of Ostrinia nubilalis in the field

Abstract

The locomotion of females of different strains of the parasitic wasp Trichogramma maidis (Hymenoptera, Trichogrammatidae) was measured under standardized conditions and compared to their efficiency in the field for several years. A manual and an automatic method for recording and analysing the locomotion of insects are described and results for differently reared laboratory strains of T. maidis are presented. The correlation between manual and automatic measurements of the travel speed was significant (r = 0.999). The automatic method was developed by means of an Image Processing System. T. maidis females were individually released in an arena, and the walking tracks were recorded by a video camera. To reconstruct the real path, a mathematical model which gives highly accurate path length estimations -termed arcus interpolation -was used. Furthermore the same programme permits the calculation of parameters like turning rate and angles, the activity pattern over the whole observation period or for selected parts of it. The locomotion of different T. maidis strains in the laboratory was compared with their efficiency in the field. An obvious relation between locomotion and parasitization in the field was apparent. The probability for parasitism of Ostrinia nubilalis Hbn.(Lepidoptera, Pyralidae) egg batches decreased linearly with increasing distance from the release point of Trichogramma wasps. The travel speed of the females of different T. maidis strains was found to be positively related to the potential for parasitism in the field. The travel speed can therefore be used as a parameter to estimate the capacity for host location and the efficiency of a T. maidis strain for inundative biological control programmes.

Quality Control of Mass Reared Egg Parasitoids

“…They chose to evaluate dispersal as a parameter because of its importance for field and greenhouse efficacy. Earlier, Bigler et al (1988) worked on this issue, and found that a correlation existed between locomotion rate (= travel speed) and parasitization (= efficiency) in the field of different Trichogramma maidis Pintureau and Voegelé strains. Although they developed a scientifically attractive approach, the methodology was rather time consuming to apply and was considered too complicated for mass rearing companies.…”

“…Since attributes like locomotory activity (Bigler et al 1988), host acceptance (van Bergeijk et al 1989), host suitability (van Bergeijk et al 1989) and temperature tolerance were negatively 1975in Switzerland (after Bigler 1994 affected by the former rearing system, we developed a new production unit. At the same time, risk evaluations of other deteriorations in the strain were performed and methods for measuring single traits and the field performance were developed.…”

Differences in the searching behaviour of two strains of the egg parasitoid Telenomus busseolae (Hymenoptera: Scelionidae)

“…Bigler et al (1988) found that differences in the speed of movement of a number of strains of Trichogramma maidis Pintoureau & Voege. in the laboratory corresponded with their performance in the field.…”

Flight activity assessment of the egg parasitoidTrichogramma brassicae (Hym.: Trichogrammatidae) in laboratory and field conditions

“…Walking behaviour of several Trichogramma strains has been studied by Bigler et al (1988), showing that there is a correlation of insect walking activity with parasitism in the field. These results imply that walking can be a useful parameter for quality control testing of Trichogramma.…”