Published on 09/17/03

Disease threatens next spring's strawberry harvest

By Cat Holmes
University of Georgia

The adage that one rotten apple spoils the barrel may hit close to home for strawberry growers in the coming year. Only in this case, it's a few infected strawberry plants that could threaten a whole crop.

A highly contagious fungus that causes anthracnose (a plant disease unrelated to anthrax) has infected the plants of a major supplier of strawberry plugs, (the trays of tiny plants that farmers transplant to their fields), said University of Georgia plant pathologist Phil Brannen.

This, coupled with the resulting higher-than-usual demand for clean strawberry transplants, could make things tough for Georgia growers. They're planting next year's strawberry crop between now and mid-October.

Anthracnose began showing up in strawberry plug beds in late August and early September in North Carolina, Virginia, New Jersey and Tennessee, according to Fruit Pest News, a Tennessee Extension publication.

Now, Georgia planters are finding the unwelcome fungus in recent shipments of plugs.

The common source of the anthracnose has been a farm in Ontario, Canada, Brannen said. However, the plugs grown from the infected Canadian runner tips may come from several operations, many in North Carolina.

"First, growers will see marginal burning on the edges of leaves, which will start to crack," Brannen said. "This is irregular leaf spot, the precursor to anthracnose."

In general, he said, the plants will be pale and stunted. Some will die.

"In the spring, the inoculum in the leaves will be passed to the flowers and fruit, which cuts back on production tremendously," he said. "Fruit rot begins before you can get to the market and sell (the strawberries)."

The problem with anthracnose, Brannen said, "is that once you bring it in, you've got it. There's no cure for it."

Ideally, growers should carefully inspect all new shipments of strawberry transplants, he said. They should destroy any plants showing symptoms of the disease.

"Preventing anthracnose from getting a toehold is ideal," he said. "But for some growers, this won't be an option. If a shipment looks halfway decent, they'll have to give it a try."

That's because, this late in the season, it's hard to find a new source of clean plants. And "for those whose bread and butter is strawberries, giving it up isn't an option," he said.

Brannen and other UGA scientists have developed a fungicide spray program they hope will help farmers pull through. Growers can learn about the spraying regimen from their county UGA Extension Service agent.

Not all strawberry growers will be affected.

Farmers transplant strawberries in one of two ways: plugs or bare-root plants. Plug plants come in trays and have an intact root ball, like any container-grown plant. They have a higher survival rate and are easier to work with.

However, plugs cost more than bare-roots, which are young plants that are simply dug up, placed in a plastic bag and overnighted to the farmer.

The anthracnose problem so far has been found in plugs. But most farmers haven't yet gotten shipments of bare-roots, said Tift County extension agent Keith Rucker.

Growers in Tift County produce 45 acres of Georgia's 280-acre, $4.5 million strawberry crop. Most Tift growers use bare-root plants, Rucker said.

Unlike plugs, bare-root plants must be planted almost immediately. So most south Georgia growers haven't yet received the shipments they will plant this fall.

"People planting bare-roots should be on the lookout for anthracnose," Brannen said. "Although we don't think the problem will be as severe in bare-rooted plants, we're concerned that anthracnose could still come in on these plants as well."

(Cat Holmes is a news editor with the University of Georgia College of Agricultural and Environmental Sciences.)

Cat Holmes was a science writer with the University of Georgia College of Agricultural and Environmental Sciences.