Garden Word of the Day
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If you have citrus trees, you probably have citrus mealybugs.
Cousin to scale insects, these tiny pests are often overlooked. At first, all you may see is some sooty mold on a few leaves, an ant trail, marching up and down the trunk of the tree, or, finally, the telltale cluster of fuzzy white, tucked under leaves or in crevices. Left unchecked, mealybugs can scar fruit, and cause chlorosis (yellowing), early leaf and fruit drop, and poor overall tree health.
Citrus mealybug varieties
There are actually four different mealybugs that attack citrus in the Bay Area:
Citrus mealybug description
All mealybugs are soft, flat, oval-shaped critters with segmented bodies. The mealybugs that attack citrus are covered with a white wax that also creates spines (filaments) around the outer edge and the back end. Unless you use a hand lens, you probably won’t notice individuals, but mealybugs colonize areas, creating white, fuzzy egg clusters that are easy to spot.
Male citrus mealybugs are not needed for reproduction, but they are needed by long-tailed mealybugs. When mealybug eggs hatch, the 'crawlers' are pale yellow, with red eyes, and distinct antennae. Crawlers are not born with their protective wax coating. They begin to excrete it soon after hatching. They are called crawlers because they crawl to a feeding site, where they will continue to develop (and damage fruit) for a month or two.
Citrus mealybug damage
Each female mealybug can lay hundreds of eggs, and there are usually two or three generations a year, so infestations can become a problem. As sapsuckers, citrus mealybugs pierce fruit, leaves, and young stems, to get at the sap. They also feed on tender, new growth. As they feed, they leave behind a trail of honeydew that attracts protective ants, and creates the perfect growth medium for sooty mold. Citrus mealybug feeding near fruit stems also leads to fruit drop. Citrus mealybug feeding also reduces fruit quality. Trees fail to thrive and are prone to infestation by disease and other pests. In addition to oranges, lemons, limes, and grapefruit, citrus mealybugs also have a taste for ornamental plants, such as tulips, coleus, cyclamen, begonias, and dahlias.
How to control citrus mealybugs
The first step to controlling citrus mealybugs is to monitor your trees, especially in spring and fall, for signs of ant trails, sooty mold, and egg clusters. Since ants will protect and farm the aphids for their honeydew, apply sticky barriers to tree trunks to block ants from protecting the aphids against their natural predators. Those natural predators are your trees’ best defense against citrus mealybugs. Ladybugs, lacewings, and hoverflies will devour these pests, so avoid using broad-spectrum pesticides. For extreme infestations, you can buy an introduced predator, called the mealybug destroyer (Cryptolaemus montrouzieri). Insecticides are not recommended. Diatomaceous earth and insecticidal soaps can be used.
Mealybugs prefer dusty conditions, so hosing trees off can make them less appealing to citrus mealybugs.
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