The Asian citrus psyllid (Diaphorina citri), or ACP for short, is an invasive insect that threatens the citrus industry because of a deadly disease — known as huanglongbing, or citrus greening disease — that it spreads to citrus trees. This insect-disease combination has cost Florida’s citrus industry $1.3 billion in losses, and production costs have increased by 40 percent.
Last year, in an attempt to prevent similar damage in their state, California researchers released parasitoid wasps from Pakistan to control the ACP, after an extensive environmental impact study was conducted.
Now a research team at the University of California, Riverside has found a new tool that targets the ACP’s olfactory system, and they’ve identified a suite of odorants (odor molecules) that the insect detects. Some of these odorants can modify the behavior of ACP and may lead to the development of tools to tackle its spread.
“The ACP olfactory system is sensitive to a variety of odorants released by citrus plants,” said Anandasankar Ray, an associate professor of entomology who led the research project. “This presents an opportunity to develop attractants and repellents using odors.”
The ACP detects citrus-plant odors using tiny sensors on its antennae. Dr. Ray’s lab performed a large-scale analysis of numerous citrus-emitted odors and identified the ones that strongly activate the neurons on the ACP antennae. Then, using a blend of activating odorants, the researchers developed an efficient attractant that could lure the ACP to sticky traps.
“We anticipate that this odor-based insect lure could be of use to growers in California and other parts of the world where ACP invasion is occurring,” Dr. Ray said.
Study results on the lures were published in PLOS ONE, and the large-scale identification of odors detected by ACP was published in Chemical Senses.
The blend of odors Ray and his team of researchers identified consisted of myrcene, ethyl butyrate and p-cymene — odors found in nature. To test whether this blend was indeed effective as an attractant, the team performed field trials on citrus trees in a residential neighborhood in El Monte, Calif. They found that the odor-based traps caught nearly 230 percent more ACPs than conventional traps placed on the same trees.
“What’s particularly encouraging is that these three chemicals are affordable, useful in small quantities, and safe for human handling,” said Dr. Ray. “They could be developed into monitoring and surveillance tools. Similar approaches can be taken to develop control strategies using odors for other insect pests of crops as well. Our study also reports identification of odors that block the ACP olfactory system from detecting citrus odors and have potential for development into repellents.”
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