Small, red delta pheromone traps (if you can find them) may also be used in April through June, depending on where you live. Check your trap every 2 weeks through November. The California Extension Office has an excellent male vine mealybug identification information sheet.
Mealybugs have been around for a long time. There is a relatively new, invasive mealybug that may be attacking your grapes.
Traditionally, California grape growers have had to watch for grape mealybugs, obscure mealybugs, and long-tailed mealybugs. These species generally do not cause significant problems, as long as their populations do not get out of hand. They are easy to recognize because of the clusters of gray, soft-bodied females gathering on the underside of leaves and in nooks and crannies. The invasive vine mealybug is another problem altogether.
Vine mealybugs (Planococcus ficus) are native to the Mediterranean areas of North and South Africa and Europe. Vine mealybugs were first seen in California in the mid-1990s and had spread to 17 California counties by 2011. Vine mealybugs are now considered a significant pest of grapes, figs, avocado, apple, bananas, mango, citrus, date palm, and several ornamental plants.
Vine mealybugs are difficult to see because they spend most of their lives protected under the bark, on roots, and around developing buds. Only during spring, when they become active again, can you sometimes see them moving away from the roots and trunk and into the leaf canopy. By summer, vine mealybugs may be found under the bark of first- and second-year canes, among fruit clusters, and under leaves. Sometimes, ants can be seen providing the mealybugs with transportation to their summer feeding grounds.
Vine mealybug description
Vine mealybug females are 1/8 of an inch long, pink, oval-shaped, and covered with a white, mealy wax that also covers filaments (spines) along the sides and posterior end. These filaments are shorter than those seen on other mealybugs, and there are no long tail filaments. Like their cousins, vine mealybugs have a segmented body. Males are tiny, winged, and you’ll probably never see them, unless you have a 30x microscope. They are 0.7 inches long, amber colored, with beaded antennae, one pair of wings, and 4 tail filaments that may stick together. It is important to know which mealybugs you are dealing with. If you see mealybugs, try to collect some and place them in a sealed plastic bag, or in a container of alcohol, and take them to your local County Extension Office for identification. This also helps authorities better understand the spread of this invasive pest.
Vine mealybug lifecycle
In summer, females lay 300 to 700 eggs in the leaves above the fruit in little pouches, called ovisacs. First instar nymphs, called crawlers, are orange and very tiny. During winter, only nymphs are present. They can be found hiding under the bark around the graft union, below the base of spurs, and around pruning wounds. There can be 3 to 7 generations a year.
How to control vine mealybugs
Being an invasive pest, vine mealybugs do not have as a many natural predators as their native cousins. Because vine mealybugs are such a serious threat to California grape growers, parasites of these particular mealybugs have been released in the state. This has helped somewhat, but eradication appears to be impossible at this point. Since these beneficial insects are unavailable to the home grower, the best things you can do to protect your vines is to inspect them regularly, especially during spring, monitor and control ant traffic with sticky barriers, and to quarantine new vines and other plants before installing them. Also, sanitize your tools regularly. Vine mealybugs also feed on burclover, malva, black nightshade, sowthistle and lambsquarters, so controlling these weeds can also help prevent infestation.
Damage caused by vine mealybugs
Vine mealybugs are phloem sap suckers that produce significantly more honeydew than native mealybugs. This honeydew attracts protective, disease-carrying ants and creates a growth medium for sooty mold on fruit clusters. These invasive pests can also carry grapevine leafroll viruses and corky bark disease. Vine mealybugs reproduce at a much faster rate than their native cousins.
Protecting your grapevine from vine mealybugs is an important step toward providing your family with fresh, delicious, organic, homegrown grapes.
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