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Warm weather means an early onslaught of pests that can harm citrus, other plants

More than 100 adult Asian citrus psyllids, invasive insects that measure about one-eighth of an inch long and can spread bacteria that can kill citrus trees, have been found in San Luis Obispo County in 2018.
More than 100 adult Asian citrus psyllids, invasive insects that measure about one-eighth of an inch long and can spread bacteria that can kill citrus trees, have been found in San Luis Obispo County in 2018. Fresno County Agriculture Department entomologist

Daytime temperatures in the 70s in late January and early February caused many trees and plants to come out of winter dormancy prematurely and quickly. Prematurely warm temperatures also caused an earlier-than-normal hatch of pest insects.

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Elinor Teague

Many citrus trees are already producing a first spring flush of new leaf growth. This is a serious issue because Asian citrus psyllids (ACP), which carry the bacterial disease Huanglongbing or HLB (also called citrus greening disease), feed on tender new citrus leaves, and the psyllids may have had an early hatch as well. Monthly monitoring of citrus trees for the Asian citrus psyllid eggs, nymphs and adults usually begins in March, but home gardeners should begin to check their backyard citrus for the presence of all stages of the psyllids now.

HLB disease is carried from tree to tree by the psyllids and can kill citrus trees within five years. It takes a year or two for the symptoms of HLB to become apparent, but the insects can pick up the bacterial disease and transmit it to other trees within a few months. Because there is no cure for HLB disease, which threatens our citrus industry, it is critical that home gardeners assist in early detection for the psyllids on their own urban/suburban trees and take preventative measures to control the Asian citrus psyllid populations. Most central San Joaquin Valley citrus trees are now under quarantine for ACP.

Look for tiny, mottled brown-winged adult psyllids about the size of an aphid feeding in a “bottoms up” position on flush growth. Open up curled or closed new leaves to check for psyllid eggs, which are very small, yellow-orange and almond-shaped. The nymphs that hatch from the eggs are really small, wingless, flat, and orangish, yellowish or brownish. The nymphs feed on sugary sap and excrete large amounts of “honeydew” that’s carried away from the nymphs’ bodies by waxy curled tubes created by the nymphs for just that purpose. The tubes are easily identifiable as belonging to the psyllids.

Chemical control of the psyllids consists of a foliar spray to kill adults and a soil drench of a systemic insecticide such as imidacloprid. Beneficial insects do prey upon all stages of the psyllids, so lesser toxic control methods including neem oil, horticultural oils and insecticidal soaps are a more environmentally aware alternative. The lesser toxic products need to be reapplied more often, every seven to 14 days when psyllids are present, to achieve good control.

If you think your citrus tree may have an ACP infestation, call the CDFA exotic pest hotline at 800-491-1899 or the Fresno County Master Gardeners’ hotline at 559-241-7534, Monday-Friday, 9 a.m.-noon. Also check the UC Integrated Pest Management website, www.ipm.ucanr.edu, under Asian Citrus Psyllid and Huanglongbing Disease for good photos and more detailed information.

Note: Mosquitos are hatching early this year as well. Check your property for any standing water in pot saucers, overturned pots, bird baths, wheelbarrows, etc. and in persistent puddles where mosquitoes lay their eggs. Mosquito larvae can live in just 1/4-inch of water. Mosquito dunks formulated with Baccillus thuringiensis israeliensis, or BTI, can be placed in ponds to kill larvae without harm to fish, birds or wildlife.

Elinor Teague: etgrow@comcast.net

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