Submitted to: Grana
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: January 25, 2012
Publication Date: November 1, 2012
Citation: Jones, G.D., Pucci, T.M. 2012. Pollen analyses of Agathirsia wasps. Grana. 51:305-317.
Interpretive Summary: Parasitic wasps contribute to crop protection by killing the larval stage of crop pests such as corn earworm, black cutworm, and fall armyworm. However, little is known about which host plants are used by parasitic wasps. Pollen was removed from 127 museum specimens of the parasitic wasp, Agarthirsia, in order to determine which host plants could help increase parasitic wasp populations near crop fields. Overall, pollen from 36 plants families, 65 genera, and 9 species was found on the wasps. However, nearly half of the pollen came from plants in the sunflower family (Asteraceae). This indicates that plants such as ragweed (Ambrosia), goldenrod (Solidago), and false-willow (Baccharis) growing near crop fields may sustain Agathirsia populations that contribute to crop pest management. Increasing parasitic wasp populations may ultimately reduce the amount of applied insecticides needed for crop protection, saving farmers time and money.
Parasitic wasps are one of the most abundant natural enemies of insect pests, and one of the most ecologically understudies groups of insects. Agathirsia is a genus of solitary, parasitic wasps that is restricted to arid regions of the southwestern United States of America and Mexico. They often parasitize the larvae of lepidopteran (butterflies and moths) crop pests. Pollen analyses were conducted on 127 museum specimens of 19 species of Agathirsia to determine possible food sources and plant taxa important to these beneficial insects. Pollen was placed into a glass slide for light microscopy (LM) or on a scanning electron microscope (SEM) stub for electron microscopy. Pollen for LM was acetolyzed and stained. Pollen for SEM was coated with gold palladium. Pollen was removed from the head of the wasps 96% of the time, more than any other part of the insect. Overall, 81% of the wasps examined with LM contained pollen and 86% examined with SEM contained pollen. Nearly 1,700 pollen grains were encountered in the LM analyses from which 117 pollen types were found in the LM analyses, with nearly half (49%) belonging to the Asteraceae (sunflower) plant family. For the SEM analyses, pollen was identified and not counted. In the SEM analyses, 88 pollen types were encountered of which 48% were Asteraceae. Pollen was identified into 36 plant families, 65 genera, and 9 species. Asteraceae pollen was identified into more genera than any other plant family (22), followed by the Fabaceae (7), and the Malvaceae (4). Common pollen taxa included Ambrosia, Artemisia, and Baccharis. Uncommon taxa included Physostegia and Sphaeralcea. Because of the large diversity of Asteraceae taxa and high number of Asteraceae pollen grains found on the Agathirsia wasps, we believe that Asteraceae taxa provide intrinsic value to crop pest management. These plant taxa will help sustain Agathirsia populations near crop fields, and ultimately reduce the amount of applied pesticides and save farmers time and money.