An attract-and-kill device for suppression of Asian citrus psyllid (Diaphorina citri) on residential citrus consists of a weather-resistant, plastic triangle treated with a contact insecticide and colored a yellow-green hue that visually attracts adult psyllids because it mimics the color of young citrus shoots that are their preferred egg-laying and feeding sites. (Photo credit: Andrew Chow, Ph.D.)

By Andrew Chow, Ph.D., and Mamoudou Sétamou, Ph.D.

This fall or winter, if you are a recreation vehicle and motorhome (RV & MH) enthusiast visiting the Rio Grande Valley of Texas, you may see yellow plastic triangles hanging in the citrus trees of your RV & MH park. These devices were conceived as a novel control system for Asian citrus psyllid (Diaphorina citri), which vectors the bacterium that causes citrus greening disease or huanglongbing (HLB). This insect-vector and plant-disease complex is presently the most serious threat faced by the U.S. citrus industry and has caused the loss of thousands of hectares of citrus orchards and billions in revenue dollars.

Area-wide management programs (AW-MP) rely on insecticide sprays for Asian citrus psyllid (ACP) control in citrus groves. However, all U.S. citrus producing states share a pressing problem with the presence of ACP and HLB in urban neighborhoods, sometimes near commercial groves. Citrus varieties that are host plants for ACP and HLB are widely planted as backyard fruit or ornamental trees in many states. The problem is that ACP adults are highly mobile and can easily fly from residential areas to infest and infect citrus trees with HLB in commercial groves. Thus, control of ACP on residential citrus is essential for reducing the spread of HLB to commercial citrus.

The Asian citrus psyllid (Diaphorina citri) vectors the bacterium that causes citrus greening disease. (Photo credit: Andrew Chow, Ph.D.)

An attract-and-kill device for suppression of Asian citrus psyllid (Diaphorina citri) on residential citrus consists of a weather-resistant, plastic triangle treated with a contact insecticide and colored a yellow-green hue that visually attracts adult psyllids because it mimics the color of young citrus shoots that are their preferred egg-laying and feeding sites. (Photo credit: Andrew Chow, Ph.D.)

Attract-and-kill devices for management of Asian citrus psyllids (Diaphorina citri) can be easily deployed on strings around canopies of residential citrus trees. (Photo credit: Andrew Chow, Ph.D.)

Adult Asian citrus psyllids (Diaphorina citri) that land on attract-and-kill devices are quickly killed by a contact insecticide. (Photo credit: Andrew Chow, Ph.D.)

In California and Texas, residential insecticide-spray programs for ACP were unsustainable due to high treatment costs, property-access issues, and public opposition. An “attract-and-kill” device for adult psyllids was the solution developed and field-tested by a collaboration of scientists at Texas A&M University-Kingsville Citrus Center, the U.S. Department of Agriculture (USDA) Agricultural Research Service, the USDA-Animal and Plant Health Inspection Service’s HLB Multi-Agency Coordination Group, and industry firm Alpha Scents, Inc. In a new report published in August in the Journal of Economic Entomology, we share findings about the impact of deploying attract-and-kill devices for Asian citrus psyllid management in residential citrus trees.

The device consists of a weather-resistant, plastic triangle treated with a contact insecticide and colored a yellow-green hue that visually attracts ACP adults because it mimics the color of young citrus shoots that are preferred egg-laying and feeding sites for psyllids. Adult psyllids are quickly killed upon contacting the insecticide after they land on the triangles. Strings of these devices can be easily deployed by homeowners or integrated pest management (IPM) professionals around the canopy of citrus trees. Under South Texas conditions, these attract-and-kill (AK) devices remain highly lethal to adult psyllids for up to eight weeks on residential citrus trees and 20 devices per tree provided significant psyllid suppression on infested lemon trees from winter to early summer.

Andrew Chow, Ph.D.

Mamoudou Sétamou, Ph.D.

Texas A&M University-Kingsville Citrus Center entomologists are presently evaluating cost-effective deployment strategies for the AK device at the scale of entire residential blocks in RV & MH parks of the Rio Grande Valley. Treating every citrus tree in an entire neighborhood or township is costly; therefore, it is important to determine whether effective psyllid suppression could be achieved by strategically deploying AK devices primarily and at higher numbers on lemon, lime, and other citrus cultivars preferred by ACP and thus more at risk of psyllid infestation and HLB infection. Park managers and residents that volunteered their trees for these studies have expressed high approval of this AK device for ACP control.

This attract-and-kill device could eventually be an effective control option for Asian citrus psyllid and complement area-wide management programs in both urban areas and elsewhere, such as abandoned citrus groves, protected natural areas where conventional insecticide control is problematic, and even along grove borders where psyllids congregate.

Andrew Chow, Ph.D., is a project director and horticultural entomologist at the Texas A&M University-Kingsville Citrus Center in Weslaco, Texas. Email: andrew.chow@tamuk.edu. Mamoudou Sétamou, Ph.D., is a professor of citrus entomology at the Texas A&M University-Kingsville Citrus Center in Weslaco, Texas. Email: mamoudou.setamou@tamuk.edu.