|Andow, D - UNIVERSITY OF MINNESOTA|
Submitted to: Biological Control
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: August 30, 2006
Publication Date: September 6, 2006
Citation: Olson, D.M., Andow, D.A. 2006. Walking pattern of Trichogramma nubilale Ertle & Davis (Hymenoptera; Trichogrammatidae) on various surfaces. Biological Control. 39:329-335. Interpretive Summary: Leaf surface structures can negatively affect the foraging behavior of many pest and beneficial species in a particular plant community. Here, we demonstrate how surface structures, such as leaf trichomes, influence the searching behavior of Trichogramma nubilale and could consequently affect searching efficiency of this important biological control agent of pest species in many crops. To do this, we first describe how T. nubilale females search on various surfaces that differ in their structure. Second, we experimentally alter the surface structure by removing trichomes to show how the trichomes likely affected searching behavior. Finally, we provide Trichogramma with experimental surfaces to indicate how surface structure likely affected searching behavior. Based on our results and published results we discuss a model of the affects of trichome density and wasp size on the searching efficiency of minute species used for biological control of pest species. We conclude that leaf surface structures will have varied effects on Trichogramma spp. and other beneficial species, and these effects will need to be considered to develop effective biological control.
Technical Abstract: Variability in leaf surface structures, such as trichomes were investigated for their affect on the pest searching behavior of the tiny wasp species, Trichogramma nubilale. We observed and recorded the walking pattern of Trichogramma nubilale females on Z. mays, Canna lily, Silphium perfoliatum, Abutilon theophrasti, Schizachyruim scoparium, a smooth and a fuzzy material, and waxed paper. For each surface type, a total of 10 mated, 1-2d old, honey-fed females were observed and their walking path was traced. Females walked fastest on waxed paper and leaves of S. scoparuim and slowest on leaves of A. theophrasti and the fuzzy material. Turning rates were high on Canna lily and waxed paper. In general, walking speed was negatively affected by the presence of trichomes and possibly the lack of leaf veins. The affect of surface structures, such as trichomes is likely to scale to the body size of the searching parasitoid. Parasitoids can walk over short trichomes, but short directionally pointed trichomes can guide the search paths in certain directions. The affects of long trichomes depends on trichome density relative to the parasitoid body length, L. When trichome density is on the same order of magnitude as L2, wasps will stand between trichomes, will frequently run into trichomes, which will retard walking speeds and increase turning. As trichome density increases further, the surface may be avoided, but when they increase to an order of magnitude of one trichome per tarsal area the parasitoid can walk on top of the trichomes.