If you snooze, you may lose in controlling vine mealybug

Vine mealybug must be a serious California grape pest if the powers at the UC Kearney Ag Center in Parlier, Calif., will not let university IPM specialist Walt Bentley rear vine mealybug in a greenhouse, but will let his peer Kent Daane established a black widow spider Disneyland vineyard on the station.

Bentley has been one of the point researchers on the vine mealybug and wanted to test materials in a Kearney greenhouse. Station managers told him he could rear grape mealybug in the greenhouse, but not vine mealybug. Too dangerous to other things in the greenhouse.

Wine grape growers and table grape growers have been aggressively battling a growing vine mealybug problem in the state. Unfortunately, Bentley told those at the annual table grape seminar in Visalia, Calif., recently some raisin growers are waiting until there is a serious problem to deal with he vine mealybug.

Waiting until it gets bad or ignoring it can result in crawler numbers of 800 per spur like Bentley found last year in a raisin vineyard in Del Rey, Calif. Numbers like that foretell a serious economic battle to control the pest that will serve as an infection point for neighboring vineyards.

Left alone, numbers like that can heavily coat grapes with honeydew and ruin the fruit; reduce sugar levels at harvest and spread diseases like leaf roll virus, Bentley told growers and pest control advisers at the table grape conference sponsored by the California Table Grape Commission and the UC Cooperative Extension.

Be ever diligent for what has become public enemy No. 1 for California grape growers, he warned. Alert workers to be on the lookout for tiny white spots on leaves, a sure sign of vine mealybug. That is also a sure way to tell a grower has a resident populations of grape or vine mealybug. Bentley has never seen a grape mealybug on a leaf, only its cousin vine.

As with black widow spiders, vine mealybug begin to move up the vine in the spring. From October until spring vine mealybug live on vine roots. Now is a good time to control the immatures with Applaud, an insect growth regulator that has proven very effective in Bentley's trials. The vine mealybugs are in a pinhead stage when they start moving out of the ground and up the vine. They are weakened from overwintering. They have no wax coating, making them very susceptible to an insecticide.

Long residual

Applaud has a three-week residual. “It certainly makes this product one that would be looked at closely when a grape farmer is approaching bud break and can no longer use Lorsban,” he said.

This plan of attack must be implemented early.

“If you have not managed vine mealybug before July, you might as well give up until later,” said Bentley.

“There is a tremendous post harvest benefit to treating vine mealybug in October and November with Lorsban,” said Bentley.

“Unfortunately Lorsban is a priority one material and on the environmental chopping block right now because of the runoff issue,” said Bentley. However, runoff should not be a major issue in vineyards irrigated with drip systems.

A post-harvest Lorsban treatment could also take care of a black widow issue in table grapes. However, the other product recommended for black widows, Danitol, is not particularly effective against vine mealybug.

Admire is a systemic material that has also proven effective in controlling vine mealybug. It requires 32 ounces of material through a drip system split in two application, 16 ounces each in April and June.

There is a new product due on the market soon. It is Movento from Bayer CropScience that Bentley says works worked as well as if not better than Applaud.

It has an uptake advantage. Unlike Admire that is taken into the plant xylem and then transmitted to the phloem where the vine mealybug feeds, the systemic Movento is taken directly into the phloem of the grape.

This new unregistered product is also effective on all growth stages of the vine mealybug.

It was even effective in a July application trial, a timing when currently registered insecticides are not effective.

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