Avocado thrips: New challenge for growers

Avocado thrips arrived in California in 1996. Since then, we have made substantial progress in our understanding of this pest. We now know the area of origin of the avocado thrips and have compiled an inventory of other potential pest thrips species on avocados in Mexico and Central America. Trials have helped us to identify several selective insecticides for use in treating avocado thrips in orchards. We have also determined the relationship between thrips densities on leaves and fruit scarring, and are studying cultural and biological control practices for use in an evolving integrated pest management (IPM) program. tific name, Scirtothrips perseae (Thysanoptera: Thripidae)(Nakahara 1997). The recommended common name is avocado thrips. Morphological comparisons have determined that avocado thrips is more closely related to Scirtothrips species in Central America than to Scirtothrips species (for example, citrus thrips, Scirtothrips citri) in North America. Furthermore, in 1971, undescribed specimens of Scirtothrips were found on smuggled avocados from Oaxaca, Mexico, at the Port of San Diego. These specimens, morphologically very similar to S. perseae, are considered to be the same species. Avocado thrips are small, slender, yellow-colored insects that are about one-sixteenth inch in length. Adults are winged but are poor fliers, and females lay eggs inside immature leaves and fruit about 1 to 2 inches long. Thrips larvae and adults can build up to such high densities on young leaves during the spring that subsequent feeding damage can cause premature leaf drop. The main source of economic loss attributable to avocado thrips is scarring of immature fruit in late spring by larvae and adults. Scarring can be severe enough to render the entire fruit surface brown, and a Mark S. Hoddle ■ Joseph G. Morse ■ Phil A. Phillips ■ Ben A. Faber ■ Karen M. Jetter