PPQ Delivers Tiny Wasps to Combat Spiking Asian Citrus Psyllid Populations

By Heather Curlett, APHIS PPQ

When Hurricane Maria thrashed the Caribbean island of Dominica last September, the storm killed dozens of people and devastated the country’s infrastructure. Adding to the misery, plant pest populations exploded after the storm passed. These insects included the Asian citrus psyllid, which spreads the citrus-killing disease Huanglongbing, also known as citrus greening. Because citrus is an economically important crop for the country, Dominica’s agriculture ministry reached out to USDA’s Plant Protection and Quarantine (PPQ) program for help.

Asian Citrus Psyllid and Citrus Greening

Citrus greening is one of the most serious citrus plant diseases in the world. Once a tree is infected, there is no cure. While the disease poses no threat to humans or animals, it has devastated millions of acres of citrus crops throughout the United States and around the world. Infected trees produce fruits that are green, misshapen and bitter, unsuitable for sale as fresh fruit or for juice. Most infected trees die within a few years.

Citrus greening is primarily spread by the Asian citrus psyllid—a small, gnat-sized insect that is no larger than the head of a pin. Once a psyllid picks up the bacterium that causes citrus greening, it carries the disease-causing pathogen for the rest of its life. An infected psyllid spreads the disease as it feeds on the leaves of citrus trees. People also help spread the disease further when they move infected plants.

Over the last few years, USDA has been investing millions of dollars in the research and development of effective tools for combatting citrus greening disease and Asian citrus psyllid. This includes developing and expanding methods for rearing and releasing biological controls—in this case, a stingless, parasitic wasp—to help reduce psyllid populations.

This wasp is showing great promise in the United States. In 2017 alone, USDA and its partners released 12 million wasps in citrus-producing states. Around some release sites, the wasps reduced Asian citrus psyllid populations by as much as 99 percent.

Read the rest of the story.

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