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What's out there at night on your farm?? An update of black light trapping (Sep. 19, 2012)

Black light trapping is an effective way to survey local insect diversity. Our original intention was to monitor Bagrada bug activity and to see if they could be trapped using black light system. We set up three locations on the farm at the Yuma Agricultural Center, 1) between a broccoli and cauliflower field 2) between a broccoli and bermudagrass field 3) in the greenhouse where our bagrada colony is located. We monitored using black lights for 12 h overnight during the past weekend. We observed no signs of Bagrada bug being attracted towards the wavelength produced by black lights. However, other closely relative stink bug species and Lygus plant bugs were found in few numbers. The majority of the insects collected in our light trap were beetles. Among them, the rove beetles (Staphylinidae) and ant-like flower beetles (Anthicidae) constituted over 90% of the beetle population. Other common beetles collected on the farm include scarab beetles (Scarabaeidae), ground beetles (Carabidae), and darkling beetles (Tenebrionidae). Crickets were extremely abundant in our light traps with several species being collected, largely because the field we selected for light trapping was not sprayed with insecticide. Interestingly, day-time active flea beetles which show great numbers in untreated broccoli fields were not caught any in our light traps. Although both Bagrada bug and flea beetle cannot be attracted by black light, insecticide applications are still effective in reducing their populations. A broccoli field during stand establishment can be e completely wiped out by the combination of Bagrada bug and flea beetle feeding if no chemicals are applied. As the cole crop growing season carries on, more leafy tissues become available and loppers and other worms will be another challenge. Monitoring of adult moth population at night using black lights will be helpful for determining increased activity, especially on organic farms.

Bugs collected using a black light
One night collection using black lights in Yuma Agricultural Center untreated field.

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For questions or comments on any of the topics please contact Marco Pena at the Yuma Agricultural Center.
College of Agriculture, The University of Arizona, Tucson, AZ.

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