Sunday, September 12, 2010
When Dick and Waynie Wingfield called me about their apples, their story was familiar. Many of the fruit had brown spots, some were misshapen, and a lot of the not-yet-ripe apples had already fallen from the tree.
The major problems affecting the Wingfields’ apples appear to be diseases called sooty blotch and powdery mildew, and damage from the feeding of codling moth larvae. The distorted growth and stunting of some of the apples could be caused by either a disease called quince rust or an insect called apple maggot.
The Wingfields, who live in rural Lecompton, planted their apple trees in the 1970s and have been harvesting fruit for most of the years since.
“We usually always have nice fruit,” Waynie says. “Every year we give a lot of them away.” The Wingfields are already worried about how to break the news to the friends and neighbors with whom they typically share their apples.
The diseases and insects affecting the Wingfields’ trees are common in the Midwest, but seem to be especially prevalent this year. Abundant spring rains and a hot humid summer provided just the right conditions for these pests.
Codling moth larvae are the worms that often feed inside apples, leaving a hole when they exit that turns brown and bruised around the edges. Dick reports that much of the affected fruit looks like it is starting to ripen before the spot turns brown and the fruit falls from tree.
Codling moth damage can be distinguished from fruit rotting diseases that cause brown spots by cutting into the fruit. A tunnel from the worm’s feeding will be apparent.
Sooty blotch and powdery mildew are more superficial. Sooty blotch causes small, greenish-gray circles that look a little like freckles all over the fruit. Powdery mildew creates brown lines in the apples’ skin, an effect referred to as russeting.
Both quince rust and the feeding of apple maggot larvae cause stunting and deformation of apple fruits. All of the pests can lead to premature fruit drop and early ripening.
“I think 500 to 600 apples have already fallen,” Dick says. “And the ones still on the tree are about three weeks ahead of schedule. We usually start picking around the end of September.”
Picking up the fallen apples and getting rid of them will help insects and disease for next year. Affected apples can be composted.
For additional control, the Wingfields will remove and destroy dead branches from the trees as they have done in the past. Dead branches often harbor disease-causing fungi. They will also do a little pruning this winter to improve air movement in the tree. Thinning will allow leaf and fruit surfaces to dry more quickly, making a less favorable environment for fungi.
For insect control, there are a few options. Paper bags placed around next year’s developing fruit will prevent codling moth and apple maggot infestations, but is a bit impractical on large trees like the ones the Wingfields’ own.
An easier method for codling moth control is to wrap apple tree trunks and lower branches in corrugated cardboard. Ideally, adult moths will pupate in the cardboard instead of the tree’s bark and can be removed and destroyed. Wrap trunks in early June and remove the cardboard in mid-July. Wrap the trunks again in early August and remove the cardboard in early winter to catch multiple generations of the insect.
Apple maggot can be controlled with round red sticky traps placed in trees from mid-June to mid-August. Apple maggot traps are readily available at garden centers and in garden supply catalogs. You will need approximately one trap to every 100 apples in your tree.
To control quince rust, remove nearby cedar trees.
Although I know the Wingfields are saddened by the loss of so much fruit, they are lucky to have missed some other disease problems. Some additional apple tree diseases that have been reported in the area this year are apple scab, cedar apple rust, black rot, bitter rot, and white rot.
Preventative fungicides and insecticides are another option for control of insect and disease problems on fruit trees. Timing and coverage are extremely important, so read product labels closely and refer to research-related guides that offer recommendations on timing for Kansas or the Midwest.
With so many apple problems this year, I’ll just be hoping I can find enough to make a good pie.