INSECT AND ARACHNID POPULATION DIVERSITY IN ONION COMPANION CROP
Applied Research
Thaddeus Gourd
Director and Agriculture Agent
Colorado State University Extension
BRIGHTON
Abstract
\r\n Onion production across the United States has been impacted by Iris Yellow Spot Virus (IYSV) which is vectored by the onion thrips (Thrips tabaci). Reducing thrips populations can sometimes help reduce infection rate of IYSV in onions. In Colorado, companion crops (living mulch) such as barley planted with onions to reduce wind and water erosion has sometimes had an effect on thrips populations. The objectives of this study are to determine 1) which thrips predators and parasites inhabit the barley companion crop; 2) what other insects/arachnids dwell in this living mulch; and 3) if there is a relationship between predator/parasite and thrips populations. Three onion field locations were sampled during 2011 that used barley as a companion crop in Weld County, Colorado. Each field location had four randomly selected areas of the field sampled with the insectavac on 6/14/2011 and 6/15/2011. Eight beneficial predator and parasite families were identified from the three fields sampled. The average of all populations of insects and arachnids at all locations revealed that ladybird beetle larva were the most numerous followed by spiders, braconid wasps, syrphid flies, big eyed bugs, ladybird beetle adults, nabids, and lacewings. Six plant feeding insect families and one phytophagous mite family were found in the field samples. Later in the season, thrips populations on 7/28/11 ranged from 0.92 to 15.4 thrips per plant. In a non-companion crop planted field, 20.5 thrips were found per onion plant. No correlation between predator/parasite and thrips populations were detected in any companion crop location.
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Poster has NOT been presented at any previous NACAA AM/PIC
This poster is being submitted for judging. It will be displayed at the AM/PIC if not selected as a State winner. The abstract will be published in the proceedings.
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Authors: T.R. Gourd, J.J. Julian
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Gourd, T. Extension Agent and Director for Adams County, Colorado State University Extension, Colorado, 80601
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Julian, J. Extension Agent and Director for Douglas County, Colorado State University Extension, Colorado, 80104