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Trapping and Monitoring for Vine Mealybug in California Grapes

Suterra Apr 8, 2020 1:59:28 PM

The vine mealybug (VMB) is a serious insect pest of grapes grown in California. There are only a few chemical management options available, and the more that these are used, the higher the likelihood is of insecticide resistance developing. Proper monitoring is a necessary step in assuring premium wine grape growers that their vines are clean and their management plans are effective.

Check out our FAQ on trapping and monitoring for vine mealybug below, written by several experts on our Technical team.

Why is vine mealybug a problem in the grape industry?

This insect is related to scale insects, aphids and whiteflies. It feeds on the sap of grape vines and produces a sticky residue that contaminates clusters with mold and degrades the value of the crop. The VMB is also directly implicated in the transmission of grape leafroll virus. Wine grape growers are especially concerned because studies suggest that the presence of the honeydew created by VMB reduces quality in wine production.

How does vine mealybug get into a vineyard?

Although the adult male VMB can fly, it is the non-flying immature insects that spread the infestation. The immature VMB, also called “crawlers,” can enter and move through a vineyard in several ways. The most direct way is at planting through infested nursery stock.

Another common transmission method is through farm equipment. Mealybug crawlers can infiltrate tractors and sprayers, or even hitch a ride on field crews that have been working in an infested vineyard or prunings and plant residue from the previous season. They can also be dispersed by birds and other wildlife, surprising even the most meticulous growers.

How do growers know whether they have a problem with VMB?

The easiest and most efficient way to detect VMB is to use pheromone traps. The best time to start monitoring is late March or early April. Suterra recommends our VMB Septa Lures loaded into our Small Paper Delta (SPD) Traps. The resulting insect sex pheromone trap looks like a little cardboard tent with a sticky liner and lure inside.

Although the lure is only attractive to VMB males, it is possible for other insects to be caught in the trap. This makes it important for the trap checker to be familiar with what male VMB looks like. The Suterra technical team is available for in-person, phone, and video consultation to assist with VMB identification. The University of California also has helpful insect identification resources online.

As the population of VMB increases, field workers will notice wet sticky patches on the trunk, leaves and clusters of a grape vine.  Later, the insects themselves will be visible as waxy white patches on the trunk, canes and in clusters.  If a vineyard is experiencing an outbreak of leafroll virus, vine mealybugs are likely associated with it.

How are pheromone traps used?

Use a minimum of two traps in a vineyard.  For vineyards larger than 40 acres, use at least one trap for every 20 acres to get the best information.  Traps are usually placed at bud swell as the season begins and need to be monitored throughout the season.  Place one trap at the center of the vineyard and one at the point where machinery typically first enters the vineyard.  This is where an infestation is most likely to begin.  Hang traps from the trellis wire where it will be in the vine canopy and mark the location with flagging tape.  Check the traps once a week to once every two weeks.  The lure is rated for one month of use and needs to be changed out on schedule as the season progresses.  The sticky trap will need to be changed if dust, debris, high insect levels, or other insects get inside it and make seeing VMB males difficult.  The trap itself will not cause the spread of VMB as it only attracts males, not crawlers.

Does my pheromone trap work if I’m catching zero male VMB?

Yes! The male VMB are very sensitive to the lure.  Clean traps suggest that your management program is working and that your vineyard is free of high populations of VMB.  Keep trapping so that any new infestation can be quickly contained. Suterra advises growers to never lower their guard. Time spent scouting the vineyard for any clues of VMB presence is time well spent.

If my pheromone trap is catching mealybugs, what are my next steps?

First, verify that it is VMB.  Gnats, thrips, leafhoppers and other little insects can also get into a mealybug trap and if they have been there for a while they may be difficult to identify.  Male VMB have large eyes and beaded, dark antennae compared to other insects.  The body is golden brown and only has two wings.  If you are unsure, take the trap out of the vineyard and let your local farm advisor or agricultural commissioner’s office have a look. The Suterra technical team is available for in-person, phone, and video consultation to assist with VMB identification.

Should I be concerned that I’m capturing VMB in my pheromone traps?

No, you are on top of things. If a pheromone trap capture is the first indication of VMB and you have not seen wet sticky stuff on the vines, the infestation is most likely small and localized and will be much easier to control than an established population would be.  This is where pheromone mating disruption for VMB will be essential for making sure that the insects don’t spread around any further.  If the males and females have trouble meeting and mating, other control measures such as natural enemies and sanitation will work in favor of reducing population. Suterra advises growers to always consult their Pest Control Advisor for pest management program, spray timings, and options on managing vine mealybug.

Can mating disruption affect pheromone traps?

Yes.  You should expect to see lower numbers on pheromone traps if the vineyard is under mating disruption. The male vine mealybug should have a difficult time finding a female adult if grower is using CheckMate® VMB-F sprayable formulation or CheckMate® VMB-XL hanging dispensers. Keep using pheromone traps as a monitoring tool to alert growers to the presence of pests before damage can be observed. 

Are there other resources to gain knowledge of mating disruption on vine mealybug?

Suterra offers a VMB Monitoring guide and product details about our mating disruption solutions. The University of California Cooperative Extension Service and the County Farm Advisor’s offices will also be good sources of information.  The Suterra Technical and Sales Teams are always available to help.

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