Strawberry IPM Newsletter
June 19, 2009
STRAWBERRY HARVEST UNDERWAY
Cool, Damp Weather Keeps Insects Low, Increases Disease Threat
Strawberry bud weevil or "clipper": Most strawberry fields are now beyond the stage where clipper can cause significant damage. Once most of the flowers are open, clipper no longer poses a threat. If you are a northern grower with any late-flowering varieties still in early bloom, keep scouting; but otherwise we needn’t worry about this pest again until next year.
Tarnished plant bugs activity has been very light this week, with none of the fields scouted being over threshold. Many fields are beyond the stage where this pest can cause significant injury. Once the green fruit has started to size up, tarnished plant bugs are no longer much of a threat. Northern growers with fields still in bloom should keep scouting, because nymph populations could still rise with warmer weather. Growers trying day-neutral varieties for late summer and fall harvest should also be aware that tarnished plant bug can be a serious pest on these plants. Once the plants come into bloom they should be scouted regularly and often to monitor for nymphs. When choosing an insecticide for day-neutral varieties pay close attention to re-entry intervals and days to harvest limitations on the product labels, because flower buds, flowers and ripe fruit may all be present at the same time.
Two-spotted spider mites: Counts of mites continue to be low in most fields, with only one field in Farmington over threshold this week. Warmer, drier weather could bring populations up as the season progresses, but at this point it is likely that control measures in most fields could wait until after bed renovation.
Sap beetles often begin to appear at harvest time. These insects chew small holes and tunnels in ripening fruit, similar to slug injury. The beetles are about 1/8 inch long and dark brown in color. They are usually found in the holes they’ve chewed into ripe fruit, but they often drop to the ground when disturbed. The best management strategy for this pest is sanitation. Keep your field free of overripe fruit by picking the plants thoroughly and regularly. Insecticide sprays for this pest can be effective, but should be a last resort during the harvest period. Brigade is registered for control of sap beetles and has a 12-hour pre-harvest interval. Nonetheless, spraying during harvest is likely to be unsettling for pick-your-own customers.
Diseases: We expect that the prolonged periods of damp weather could make this a challenging season for keeping gray mold under control. It has been difficult to keep flowers and fruit protected from Botrytis with frequent wet weather and irrigation needed for frost control. It is still important to keep the plants covered with a fungicide during post bloom period when frequent wet weather occurs.
Anthracnose fruit rot could become a problem if the temperatures become warmer with the wet field conditions that are prevalent. This fruit rot is favored by warm, humid conditions and can spread rapidly with rain or irrigation, especially if there is any standing water in the field. Anthracnose fruit rot is characterized by black sunken lesions on the fruit. Fungicides that offer control of anthracnose include Abound, Cabrio and Switch.
Powdery Mildew: We have been seeing symptoms of powdery mildew in most fields in the past two weeks. Periods of wet weather can stimulate symptoms of this fungal disease on strawberry plants. The most obvious indication of this foliar disease is the upward curling of the leaves. Purple or reddish blotches, and/or white, powdery growth may be observed on the undersides of the leaves. Mildew infections weaken plants and can reduce yield the following year. Some varieties are more susceptible than others, for example Annapolis is quite susceptible, while Mira and Mesabe are thought to be resistant. Abound, Captan, Pristine, Cabrio, Topsin-M and Stylet oil are presently registered to control powdery mildew.
Review: Keeping Strawberries Fresh for Market
If you‘re bringing fruit to market, make sure that it arrives in the best condition possible. Strawberries cool most efficiently if harvested early in the morning while they are still cool. Place fruit into refrigerated storage quickly and keep it out of direct sunlight. Fruit should be stored at 32 Fahrenheit and 95% relative humidity. Cold air should be moved through the boxes or flats of fruit with a circulating fan and/or exhaust fan to cool most efficiently. Temperatures lower than 32 may freeze the fruit and ruin its fresh quality. A small, well-insulated building cooled with air conditioners and fans can provide effective temporary storage for strawberries. If you don’t have refrigeration facilities, keep the fruit as cool as possible by harvesting when air temperatures are cool, and keeping it out of direct sunlight. Transport the fruit to market as quickly as possible, and harvest only what you think you can sell in a day.
Twilight Meeting Next Week!
The University of Maine Cooperative Extension and the Maine Vegetable and Small Fruit Growers Association are holding a twilight meeting at Flaherty’s Family Farm in Scarborough on Thursday, June 25th at 6:00 p.m. Come visit Flaherty’s first-class farm stand and new greenhouse facilities, in addition to their fields of vegetables. Jack Flaherty and family will guide us through the farm, and Dr. Jim Dill, University of Maine Pest Management Specialist will discuss pest monitoring and control for greenhouses. Flaherty's Family Farm is located at 116 Payne Road in Scarborough, just off of Highway 95 at exit 39.
David T. Handley
Vegetable & Small Fruit Specialist
Highmoor Farm
P.O. Box 179
Monmouth, ME 04259
(207) 933-2100
Pest Management Office
491 College Ave
Orono, ME 04473
1-800-287-0279
If you are a person with a
disability and will need any accommodations to participate in the programs mentioned in
this newsletter please call 207-933-2100 to discuss your needs.
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Published and distributed in furtherance of the Acts of Congress of May 8 and June 30, 1914, by the University of Maine Cooperative Extension, the Land Grant University of the state of Maine and the U.S. Department of Agriculture Cooperating. Cooperative Extension and other agencies of the U.S.D.A. provide equal opportunities in programs and employment.