Historically, people frequently brought species of plants and animals with them from their native lands to California, either accidentally or intentionally. Some introductions did unexpected damage while others had positive outcomes (food and horticultural crops).

Many invasive plant problems began as ornamental plants for sale by nurseries and garden centers or as host for insect pests (silver leaf whitefly on poinsettia, vine mealybug on nursery plants). Today, exotic and invasive pests, including plants still make their way into California through commercial nurseries, import trade and national and international travel.

Many exotic and invasive pests are of major concern in California. The glassy‐winged sharpshooter (an insect) and purple loosestrife (a weed) are two invasive species that are established in some areas but still threaten to invade other areas.

Invasive species of concern to California’s grape industry include European grapevine moth (EGVM) and light brown apple moth (LBAM), have not yet established themselves in all grape growing areas, but have already been costly to the state and the grape industry.

Invasive pests costly to growers

One of the worst invasive insects in California, vine mealybug (Planococcus ficus), continues to cost growers substantially in time, management and lost yields. It was first identified in California’s Coachella Valley in the early 1990s and continued to spread north into the southern San Joaquin Valley in 1998. Now established in over eighteen counties, VMB control has become a standing insect management cost for growers annually. Vine mealybug (VMB) is also an economic pest of vineyards throughout the world.

All VMB life stages can be found year‐round in an infested vineyard. During winter months, VMB eggs, crawlers, nymphs, and adults are found under bark, under developing bud scales, and on roots. Most are found on the lower trunk near the soil line and on roots. As temperatures warm in spring, VMB increase in numbers and become more visible. This is due to increased reproduction and movement from the trunk to the cordons and aerial parts of the vine.

By late spring and summer, they are found on all parts of the vine: under bark, on trunks and cordons, on first‐ and second‐year canes, leaves, clusters, and roots. In the Coachella Valley, the numbers of VMB are largest in mid to late spring and decline dramatically (two‐ to tenfold) in midsummer. In the San Joaquin Valley, the increase in numbers begins in late spring with peak densities occurring from the end of June through the middle of August.

Several species of ants can be found in association with the vine mealybug. The ants have been observed transporting VMB around on the vine, feeding on the honeydew produced, and fending off natural enemies.

Because five different mealybugs impact grapes, it important for growers to know what type is in their vineyard. Each have peculiarities in development and periods of greatest susceptibility to chemical management. Growers should have mealybugs properly identified by their local UC Cooperative Extension office, Agricultural Commissioner or California Department of Agricultural entomologist. Proper identification will ensure that the best management strategies can be implemented for the mealybug of concern (More information can be found in Mealybugs in California Vineyards; ANR 21612)