Don Luvisi
UCCE Farm Advisor, Kern County
Viticulture - Grapes
May 21, 1999
New Mealybug Species Found in Kern County
Abundant populations of mealybug have infested a vineyard in southeastern Kern County. This infestation resulted in an unusual amount of honeydew as observed by the sticky, shiny trunks and cordons. The large number of visible mealybugs and honeydew was not characteristic of grape mealybug. Based on these observations, samples were taken and sent to the California Department of Food & Agriculture's Plant Pest Diagnostics Center. Dr. Ray Gill, Homopteran expert, determined the specimens to be the vine mealybug, Planococcus ficus. This find, recorded 7/31/98, is the first record of vine mealybug in the San Joaquin Valley. Planococcus ficus is a B rated pest with no current quarantine requirements attached with the possible exception of nursery stock.
Vine mealybug is currently a pest of grapes in Coachella Valley resulting in significant losses related to quality. This phloem-feeding insect extracts proteins and sugars from the vine excreting the sugars in the form of honeydew. The honeydew creates a sticky sugar residue on bunches and, under some circumstances results in the growth of sooty mold. No economic losses resulting from competition for vine resources have been documented in California populations.
The vine mealybug has a broad climatic distribution with origins in the Mediterranean and currently including irrigated desert and tropical regions. The documented host range includes figs, mangos, avocados, pomegranates and grapes. In California only grapes are recorded hosts at this time. Much more information is needed to understand how this exotic pest will spread and develop under the climatic conditions of the San Joaquin Valley; however, we may be able to look towards grape mealybug for some generalizations. The spread of vine mealybug throughout Kern County may increase production costs and pesticide usage. Current experience has been in table grape production, but wine and raisin grapes are also at risk with this aggressive mealybug.
Grape and vine mealybugs are very similar in appearance, therefore requiring expert identification. However, differences in their distribution on the vine can help to determine what species is present. Current infestations of vine mealybug appear to be more severe than that of the grape mealybug, including large masses of mealybugs on old wood, canes, leaves, roots and fruit. Grape mealybug will not be found on the leaves and roots. According to observations in Coachella Valley, vine mealybug is present throughout the year on all aerial parts of the vine.
At this time, the vine mealybug has been verified in five Kern County and two Fresno County vineyards. The 60 to 70 mile spread between locations can attest to the ability of this pest to hitchhike on trucks, trailers, farm equipment, plant material and table grape packing pans, tables, etc. If vine mealybug becomes entrenched in wine grape vineyards, it could be easily spread by mechanical harvester gondolas, etc.
The spread of this pest needs to be limited through an aggressive field control program using available registered pesticides. In addition, the following precautions should be followed by all growers.
1) Awareness that this is a new pest that is adapted to spreading by man.
2) All equipment from infested vineyards should be steam cleaned and/or washed prior to transport.
3) Packing trailers, picking pans, shoes and even clothes, need to be washed and/or cleaned before moving to a new or uninfected field. The vine mealybug is farther out on the canes and leaves than the grape mealybug and can contaminate clothing.
4) Cull fruit being transported to crushing facilities can also spread the vine mealybug.
PCA's and growers need to carefully inspect all vineyards, and especially those with mealybug infestations. If any doubt exists as to which mealybug it is, bring samples to the Farm Advisor's Office in Madera, Fresno, Kings, Tulare or Kern Counties. Samples should be preserved in alcohol and the small vials labeled for name, and location of find. The samples will be sent to entomologists for identification.
Your help is needed since this is part of a coordinated program to assess the spread of this new pest.