REVIEW ARTICLE ▼ Vineyard managers and researchers seek sustainable solutions for mealybugs, a changing pest complex ▼ by Kent M. Daane, Monica L. Cooper, In an uncontrolled vine mealybug Serguei V. Triapitsyn, Vaughn M. Walton, infestation in a San Glenn Y. Yokota, David R. Haviland, Joaquin Valley raisin- Walt J. Bentley, Kris E. Godfrey grape vineyard, mealybug and honey- and Lynn R. Wunderlich dew accumulate on the fruit, canes and leaves. Mealybugs have become increasingly important vineyard pests — a result of their direct damage to the vine, their role in transmitting grapevine leafroll viruses, and the costs for their control. Numerous mealybug species are found in vineyards, and each has ▼ An obscure mealy- different biological traits that af- bug infestation fect sustainable control options. We in a Central Coast wine-grape vineyard review the mealybug pests and their shows growth of sooty molds that are natural enemies to provide some often associated with clarifi cation about current trends in mealybug excretion (honeydew), espe- biological control tactics and needed cially in cooler grape directions for future work. regions. ver the past 100 years, a series of different mealybug species have beenO found in California vineyards, with fi ve species currently causing damage and a sixth posing a threat. Mealybugs have needlelike mouth- specimens collected on coastal buck- Mealybug pests parts that feed on the plant’s phloem, wheat in California in 1900 and was which contains the nutrients needed Most of California’s vineyard mealy- the only vineyard mealybug thought to for mealybug development. As mealy- bugs are invasive species — although be native to North America (Miller et bugs digest their food, they excrete a some of them have been here for nearly al. 1984) until the arrival of Ferrisia gilli sugar-rich fl uid called “honeydew.” 100 years. For newly invasive species, Gullan. Grape mealybugs can be found All vineyard mealybugs can feed on eradication should be the fi rst response. throughout California’s Central Valley the vine’s trunk, canes, leaves or fruit, If eradication is not feasible, then an and coastal grape regions, as well as and some species feed on vine roots. integrated program that includes clas- in Oregon and Washington vineyards. Crop loss occurs when mealybugs sical biological controls should be con- Typically, there are two generations per infest fruit or excrete honeydew that sidered. For native mealybug species, year (Geiger and Daane 2001). For most covers fruit and leaves, often result- resident natural enemies often provide of the year, grape mealybugs are found ing in sooty mold growth, defoliation substantial control or can be manipu- under the bark, but during the second and sunburned fruit. Continuous high lated to improve their effectiveness. generation (beginning in June) they levels of infestation over successive The history of each mealybug species in move into grape clusters, especially years may also lead to the deteriora- California and its distinctive biological clusters in contact with the trunk or tion of vines. And many mealybug characteristics affect the level of eco- spurs. The population overwinters as species transmit viruses such as grape- nomic damage and potential effective- eggs or small nymphs under the bark, vine leafroll (see sidebar, page 174). ness of biological controls. with a required diapause that helps to However, these mealybug pests can be Pseudococcus. The grape mealybug, synchronize generations each year. controlled, to some extent, by natural Pseudococcus maritimus (Ehrhorn), is one The longtailed mealybug, Pseudo- enemies that are often present in sus- of the oldest California vineyard pests coccus longispinus (Targioni Tozzetti) is tainable management programs. (Essig 1914). It was fi rst described from believed to be of Austro-Oriental origin http://CaliforniaAgriculture.ucop.edu • OctOber–December 2008 167 A B Africa, South Africa, Argentina, the Middle East and Mexico. In California, crawlers blown by wind or carried by animals and farm machinery aid its spread. Infested nursery stock (Haviland et al. 2005) and pomace from the wine-grape crush (see sidebar, page 172) can also harbor this pest. Vine mealybug has a number of traits that make it particularly dam- C D aging and difficult to control. Most notably, there are four to seven annual generations in much of California’s grape-growing regions, resulting in rapid population growth. Vine mealy- bug also feeds on all parts of the vine throughout the season, resulting in a portion of the population protected under the bark. It can feed on a num- ber of plant species; however, while it is common in Europe on fig Ficus( sp.), Common mealybug species in vineyards there are no reports on this host from E are (A) grape mealybug, with orange-to- red ostiolar secretion near the head and California. The closely related citrus anus (the fluid is often a defensive tactic to mealybug, Planococcus citri (Risso), has ward off predators); (B) obscure mealybug; been found on vines but has never been (C) longtailed mealybug; (D) vine mealybug recorded as an economically important approaching a grape berry; and (E) Gill’s mealybug with glasslike rods brushed pest in vineyards. aside to show adult wax pattern. Ferrisia. Ferrisia gilli Gullan is a close relative of the striped mealybug (F. virgata Cockerell), which is probably native to southeastern North America. In fact, until recently the California population was considered to be the (Ben-Dov 1994). This cosmopolitan spe- Biological traits that make obscure striped mealybug, but differences in cies has been resident in California since mealybug more damaging than grape its adult morphology and economic at least 1933 and is best known as a pest mealybug are that it readily feeds on importance in pistachios and almonds of ornamental plants. Longtailed mealy- leaves (causing leaf damage and rain- prompted studies that led to its new bug has been limited to Central Coast ing honeydew down onto grape clus- species description in 2003 (Gullan et vineyards, where it has three generations ters), it can survive on common weeds al. 2003). Damaging vineyard popula- yearly. Unlike the other Pseudococcus spe- such as malva and burclover (Walton tions have only recently been found in cies discussed, longtailed mealybugs give and Pringle 2004b), it has three or four the Sierra foothills. Because F. gilli — birth to live crawlers (1st-instar mealy- overlapping generations per year, and commonly called Gill’s mealybug, after bugs, which disperse before they settle it excretes more honeydew. It is limited, Raymond Gill — is so new to scientists, and feed) rather than depositing eggs. however, to the cooler grape-growing research on its seasonal occurrence The origin of the obscure mealybug, regions, and is most commonly found in has, to date, only been conducted on Pseudococcus viburni (Signoret), is un- Central Coast vineyards. pistachios grown in the Central Valley known, and both Australia and South Planococcus. The vine mealy- (Haviland et al. 2006). There, the mealy- America have been suggested. While bug, Planococcus ficus (Signoret), is bug has three annual generations. In known to be in North America since a relatively new invasive species to fall, adult females produce crawlers that the early 1900s, its history is poorly Californian and Mexican vineyards overwinter in protected crevices of the documented due in part to earlier taxo- (Daane et al. 2006). In 1994, it was trunk and scaffolding branches. During nomic confusion — it is a close relative found in Coachella Valley table grapes, bud-break, the overwintering nymphs of the grape mealybug and was often although it probably entered the state migrate to buds to feed; they become misidentified (Miller et al. 1984). The years before. Vine mealybug has al- adults between late May and mid-June obscure mealybug is primarily a pest of ways been associated with vineyards and give live birth to crawlers, the first ornamental plants but is also found in and was first identified as a new spe- of two in-season generations. Currently, coastal vineyards, especially in associa- cies in the Crimea on grapes in 1868. It studies are ongoing in El Dorado tion with the Argentine ant, Linepithema has since spread and is now a key pest County to determine this mealybug’s humile (Mayr) (Phillips and Sherk 1991). in the vineyards of Europe, northern seasonal occurrence on grapes. 168 CALIFORNIA AGRICULTURE • VOLUme 62, NUmber 4 Maconellicoccus. The pink hibiscus A B mealybug, Maconellicoccus hirsutus (Green), is an excellent example of an in- vasive species that presents a significant threat to California grapes but has been limited by a successful classical biologi- cal control program (Roltsch et al. 2006). Pink hibiscus mealybug is probably native to Southeast Asia or Australia. It invaded Egypt in 1912, Hawaii in 1984, the Caribbean islands in 1994, Florida in 2002, and reached northern Mexico C D and Southern California in 2003. It has a wide host range of more than 200 plant species. Under optimum temperature conditions, this mealybug can have explosive populations with more than 600 eggs per ovisac and up to 15 genera- tions per year. Natural enemies Hundreds of natural enemies can Common mealybug predators include lady beetles. (A) An adult Scymnus species feeds on a attack mealybugs, making this brief grape mealybug. (B) A large mealybug destroyer larva near the smaller obscure mealybug; review incomplete. Here, we catalog the larvae of many of these lady beetle species have waxy filaments to mimic mealybugs and the more common natural enemies and reduce interference from mealybug-tending ants. (C) A cecidomyiid larva prepares to feed on their potential impact. grape mealybugs. (D) A third-instar green lacewing (Chrysoperla carnea) larva attacks a grape mealybug, prompting it to secrete a ball of red ostiolar fluid in defense. A number of predators contribute to mealybug control; a few specialize on mealybugs, while most are general- Other beetles.