Vineyard Mealybugs

The GMB population is mostly in the 2nd instar stage at vineyards in Pope Valley and Oakville. We are still finding some 1st instar GMB.

We found GMB under the bark (on canes and spurs) and also on the leaves. 

We continue to find mainly 1st instar GMB in vineyards we are monitoring from Pope Valley to Oak Knoll. We found all of our GMB under the bark of spurs and/or canes. We have not yet found GMB on the leaves, although we could expect to see them on the leaves with next week's warmer weather.

If you are planning to use an insect growth regulator (Applaud) to treat this overwintering generation of GMB, it will be important to make your applications while we still have young instars in the field (in the next couple of weeks).

According to Lucia Varela, UC IPM Advisor, these applications for GMB usually occur when there is between 6 and 10 inches of shoot growth--while we have mainly 1st and some 2nd instars in the population. It is not necessary to have all of the population exposed on the leaves, as there should be some activity of Applaud against a population on the canes or spurs.

We found GMB on spurs (spur pruned) and canes (cane pruned) in Pope Valley, Oakville, and Oak Knoll. We found a few hatched eggs under the bark of the trunk in Pope Valley. Otherwise, 100% of the live GMB that we found are 1st instars (crawlers).

We continue to find mainly 1st and 2nd instar grape mealybugs.

In Pope Valley and St. Helena, we found GMB nymphs on leaves, in clusters, and under the bark of the cordon.

At our Oak Knoll sampling site, we did not find GMB nymphs on leaves or in clusters, solely under the bark of the cordon.

Nymphs will move into the clusters to feed and mature. Mature females will then return to the bark to lay eggs, which are the overwintering stage of GMB.

We are seeing the overlapping generations typical of vine mealybug populations in the summer months. 

All life stages are present at all of our sampling sites.

At the Carneros site, we found a few VMB on the leaves, but the majority of the population at all sites remains under the bark.

We are catching males in UC traps, and so are staff of the Ag Commisioner in their traps.

Most of the summer generation of the GMB has hatched.

At our sampling site in Pope Valley, 69% of the sampled population was in the egg stage on July 11, 2011. By July 21, 2011, only 14% of the sampled population remained in the egg stage. A small percentage of the crawlers had moved out onto the leaves, but most remained under the bark on July 21, 2011.

At our St Helena sampling site, only 2% of the sampled population remained in the egg stage on July 22, 2011. The hatched crawlers were found principally under the bark of the arms and cordon, with a few remaining on the trunk. We also found one GMB 1st instar on the fruit, on a berry of a cluster that was in direct contact with the cordon.

As the summer generation develops, the nymphs will move into the fruit to feed.

Crawlers of the summer generation are starting to hatch. We found 15 ovisacs: crawlers were hatching from 3 of these, but not from the other 12 ovisacs. 

These are the very early stages of egg hatch. The hatched crawlers were still located under the bark. We did not find any GMB activity on the leaves or in the clusters. Eventually, nymphs of the summer generation will move to the fruit and foliage to feed.

Once the nymphs move to the fruit and foliage, this will be the appropriate timing for a contact or IGR insecticide application targeting the summer generation. Systemic insecticides should have already been applied for this generation.

We are seeing increasing evidence of activity of natural enemies: both predators and parasitic wasps. We found larvae, pupae, and an adult of the mealybug destroyer beetle (Scymnus). Unwarranted insecticide applications should be avoided to minimize disruption of natural enemy populations.

VMB populations remain mostly synchronous at our sampling sites in St. Helena. The majority of the population is in the 1st or 2nd instar stage. We did not find any movement onto the leaves, although we may see some following the predicted warm weather. We are finding some evidence of parasitism at both sites.

VMB populations at our Carneros site are not as synchronous. We are finding mostly 2nd and 3rd instars, but a smattering of females, ovisacs, and 1st instars are also present. The Carneros population is also under the bark. We also found healthy populations of Argentine ant on the vines in Carneros with VMB.

The GMB population is in the adult (female) and ovisac stages, at vineyards we are monitoring from Oak Knoll to St Helena, and into Pope Valley. Nymphs hatching from these ovisacs will move into the clusters to feed.

Last week we began to see more evidence of activity of biological control agents, both parasitic wasps and predators. 

For those concerned about GMB as a vector of leafroll viruses, this will be the appropriate timing for insecticide applications. 

Spirotetramat (Movento) applications may be most appopriate during this stage (egg development). 

The appropriate timing for application of insect growth regulators (Applaud) is at or just after egg hatch. Insect growth regulators are most effective against young mealybugs (1st and 2nd instars).

Contact neonicotinoids (such as foliar applications of Clutch and Venom, Assail, Actara, and others) may be applied at or after egg hatch. Contact insecticides may be applied up to harvest (respecting pre-harvest intervals), although efficacy may be reduced after bunch closure when it is more difficult to contact mealybugs feeding in the clusters. 

Organically registered materials also typically have contact activity, so are most appropriate after egg hatch, or during the young instar nymph stages.

Insecticide applications may disrupt natural enemies that attack GMB. Unwarranted insecticide applications should be avoided to conserve natural enemy populations.

VMB eggs are hatching at all vineyards we are monitoring in Carneros and St. Helena.

92% of the VMB population at the block in Carneros is 1st instar;
60% of the VMB populations at the blocks in St Helena are 1st instar.

In Carneros, all VMB life stages were found under the bark. In St Helena, some 1st instars were found on leaves.

The first flight of male GMB has started in Napa County.

We are seeing mainly 3rd instars and females on vines in Oakville and Oak Knoll. We have not seen any egg-laying yet (no ovisacs found).

We found GMB on the leaves and the base of the shoots.

We also started seeing a sizeable population of predatory mites at our Oak Knoll site this week.

For growers concerned with GMB as a vector of grapevine leafroll virus, this is the first treatment window for insecticide applications. (This may not include Movento applications that require an expanded canopy for translocation).

Pesticide applications may disrupt natural enemies that attack GMB. Unwarranted applications should be avoided to conserve natural enemy populations.

Vine mealybug populations in Carneros are very synchronous right now. We found mainly adults. Most of the adults were laying eggs. We could expect egg hatch within a couple of weeks.

As the eggs hatch and crawlers emerge, that will be an appropriate window of insecticide applications (both chemigation and foliar applications). For information on insecticide efficacy for VMB visit http://ucanr.org/CESonomaMBcontrol

We also found many adults and egg sacs at the St Helena site. Some of the eggs have begun to hatch, and we also found crawlers at that site. At this St Helena site, development is slightly more advanced than in Carneros.

VMB development may vary by site. It is best to understand the populations in your vineyard to inform management decisions.

We sampled GMB at the end of last week (Apr 21, 22).

At our Oakville site, 100% of the GMB population was on the spurs. They were 1st and 2nd instars.

At our Oak Knoll site, 90% of the GMB population was on the spurs and 10% of the GMB population had moved onto the leaves. They were 1st and 2nd instars.

Insecticide treatments are most effective against exposed mealybugs (on the leaves). For growers concerned with GMB as a vector of leafroll virus, the first treatment window for foliar insecticide applications is approaching and will be optimal when the GMB are exposed on the leaves. (This does not include Movento applications, which require a more expanded canopy for absorption). 

In vineyards where leafroll virus is not a concern, and GMB populations are not economically damaging, avoid unwarranted insecticide application to protect the GMB natural enemy complex.

VMB populations at St Helena and Carneros sites tended to be 2nd instars and Females.

We scouted for GMB in Carneros, Oak Knoll, and Oakville.

We found 1st and 2nd instars. They were under the bark of the spurs, at the base of the spurs, and on the arms. We have not found any moving onto the leaves yet, but we expect this will occur soon.

We will be scouting for VMB in Carneros and St Helena on Friday, 15-Apr.

We sampled VMB in St Helena, 21-Mar-2011. We also planned to sample Carneros this week, but the weather did not cooperate.

All VMB were found under the bark, mainly on the trunk, from the soil line to the head.

GMB are getting ready for spring!

At vineyards from Oak Knoll to St Helena, we found most of the population (92-100%) is in the 1st instar stage.

In Carneros, we found both 1st and 2nd instars (47% and 42%, respectively).

At all sites, GMB were found on the spurs; they are positioned to move onto the leaves soon after the vines break bud.

Weather permitting, we will report next week on VMB.

We sampled grape mealybug Feb 8-14, in Carneros, Oak Knoll, and St. Helena.

100% of population in Oak Knoll and St Helena vineyards were in the egg stage.

The majority (52.6%) of the population in Carneros was in the 1st instar (crawler) stage under the bark.

We will be out sampling again Mar 14-18, to issue another report the week of March 21.

The purpose of this newsletter is to provide information on the life cycles of vineyard mealybugs in Napa County.

The two mealybug species of interest are the grape mealybug (Pseudococcus maritimus) and the vine mealybug (Planococcus ficus).

We will follow the development of these species through the growing season, and issue reports on the life stages found in vineyards of Napa County.