Apple Scab.. Highmoor Farm Agricultural and Forest Experiment Station. Tuesday, June 23, Vol. 23:15

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Camilla Morton
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Highmoor Farm Agricultural and Forest Experiment Station Tuesday, June 23, 2015. Vol. 23:15 Apple Scab.

About half of those potential lesions have now had enough time to show up as secondary infections which spread from primary infections.

1 Highmoor Farm Agricultural and Forest Experiment Station Tuesday, June 23, Vol. 23:15 Apple Scab.. For orchards south of Bangor, almost all potential lesions from primary scab infection periods have now had enough time to become visible as dark green, brown or black spots on leaves. About half of those potential lesions have now had enough time to show up as secondary infections which spread from primary infections. This is important where primary infections in tops of larger trees can be hard to detect. Until those potential primary infections have had time to spread as secondary infections, you cannot be sure that scab control was effective. If you have trees less than feet tall, and have checked for scab and found none so far, then a longer interval between fungicide applications should not lead to problems, as other fungal disease threats are low at this time. However, going without protection requires frequent checking of the orchard to react quickly to prevent a scab outbreak from spreading before protection can be applied to suppress it. Finding 5 or fewer leaves with one or more scab lesions per 100 terminals and fruit clusters (with each terminal cluster consisting of a quick glance at about 15 leaves) is considered clean enough that long fungicide interval targeting flyspeck and sooty blotch will keep scab in check. More than 18 leaves with scab per 100 terminals/fruit clusters is considered enough scab to require at least scab shutdown treatments with a either paired Syllit, DMI / sterol inhibitor (e.g. Inspire Super, Indar), or strobilurin (Flint, Sovran, Pristine) treatments a week apart. Those shutdown treatments should be followed by three weeks of strong protective captan coverage (i.e. ca. 10-day interval between applications, longer or shorter depending on rain frequency and amounts.) The idea is to suppress production of conidial spores, and to maintain a barrier against conidia that are produced from being able to start another generation of infections. After a month, conidial production by the original lesions should be diminished and allow going back to a normal fungicide regime. Hot (i.e > 80F) dry weather is ideal for burning out scab. The next 3 days look nice and dry, but Saturday June 27 through July 7 looks to be a period of cool wet weather ideal for existing scab infections to spread on unprotected fruit and foliage. If you have active scab in the orchard it will be important to have protection in place during that time.

2 Fire Blight.. Fire blight strikes have been confirmed in several Maine orchards. One grower noted that you can check a tree in the morning and not find fire blight, then find a strike on the same tree in the afternoon. Ruthless perseverance in removing strikes can shut down a substantial fire blight outbreak. If there are more strikes than you can reasonably prune out in a timely manner, it may not be worth doing so and let nature take its course. Fortunately, I do not know of any blocks in that situation this year. Spread of fire blight naturally slows down once trees reach terminal bud set in late July. If you have any fire blight strikes, it would be prudent to have streptomycin on hand in case you need a rapid response treatment within 24 hours after a hailstorm to prevent spread of fire blight into wounded leaf tissue. If you find active fire blight, you can have samples tested to confirm fire blight and screen for streptomycin resistance. To do so, send a message to glen.koehler@maine.edu. The staggered bloom this year in many blocks combined with hot weather at the tail end of bloom (the worst time to get blossom blight infection weather because flowers have had plenty of time to get inoculated) has resulted in new members of the I ve had fire blight club. Getting out of this club is harder than getting in. Once you have had fire blight, for the next two seasons winter pruning to remove ugly stub cuts from the previous summer, copper at Green Tip, having streptomycin and Regulaid on hand in case of another rapidly developing bout of blossom blight weather, and growth management to prevent overly lush growth, and perhaps use of Apogee to suppress vegetative growth on established trees, should become part of your management plan. Thinning Update.. As of Friday, June 19, orchards in northern Maine were still within the chemical thinning window, but with light fruit set on most trees, additional thinning is generally not needed if a thinner was previously applied. If no thinner has been applied yet, then carbaryl or NAA (Fruitone or PoMaxa) at a low dose is recommended for return bloom. BA (Maxcell) is another option. A low dose will not cause much thinning in the currently cool weather, but can prevent biennial bearing. Signs of good thinning are evident in southern Maine, but the amount will vary depending on how much thinner was applied and when. At Highmoor Farm, thinning seems to be adequate in most orchards. Honeycrisp and Golden Delicious in our orchard will probably need some hand thinning, but the cropload was reduced to a reasonable amount by thinner applied three times. Thinners worked better than I thought for us, and I hope for others, as well. Late bloom or secondary bloom was common on most varieties this year. One of our antique apples still had a number of open blossoms on June 19. The rapid shift from cool to hot weather in May may have increased the occurrence of staggered bloom.

3 Insects and Mites.. What appears to be apple leaf curling midge damage to leaves has turned up in a couple of orchards over the past week. The leaf margins are tightly rolled and become brittle. Inside the rolled leaf edges, you may find pinkish white maggot-like larvae. Apple leaf curling midge is not an economic problem and not worth control on established trees, and by the time you notice them, natural predators may be bringing them under control. If numerous on young trees for which you desire maximum growth, insecticide application for apple maggot, codling moth or Lepidopteran (caterpillar) leafrollers will provide control. Potato leafhoppers cause another type of leaf margin damage, where the outer leaf margins turn yellow and the leaves cup upward. In addition, PLH feeding can cause shoot tips to wilt, resulting in a shepherd s crook dieback that is easily confused with fire blight. If still present, PLH will be yellowish-green 3mm long adults that fly up when disturbed, 2mm long yellow nymphs that walk sideways on the undersides of leaves. Plum curculio immigration into orchards from surrounding hardwood forest is over for the year. Larvae that successfully grow in apples will cause drops from which adults will emerge in August, but they are not economic pests and will look for a place to overwinter before causing significant damage. Codling moth egg hatch will begin over the next two weeks in southern to northern Maine. At least one full block insecticide, plus one or two perimeter insecticide applications made for plum curculio, seems to provide adequate codling moth control for most orchards. But in organic or low spray orchards where carbaryl was not used as a thinner, and at least one full block insecticide effective against codling moth was not used, then codling moth can cause extensive damage. Organic options include Bt (Dipel, Javelin, Xentari etc.), Entrust, azidirachtin formulations (e.g. Neemix, Aza-Direct), Cyd-X (granulosis virus), and Surround. Pyganic is an organic option, but is best used as a supplement to another material due to its lack of residual control. With warming temperatures in July, weekly scouting for European red mites and Twospotted spider mites is needed to be able to respond quickly before leaf bronzing occurs. In July, the recommended treatment threshold rises from 2.5 to 5 living-hatched-mites (i.e. don t count eggs or dead mites) per leaf, or 75% of middle-aged leaves with one or more mites. July 22 Summer meeting and orchard tour. This year s tour will be at the Highmoor Farm Agricultural Experiment Station in Monmouth, on Wednesday, July 22 from 9:00am to 3:00pm. AGENDA 9:00 am Registration, $20 per person*** 9:30 Welcome and Opening Remarks Fred Servello, Maine Agriculture and Forest Experiment Station John Rebar, Cooperative Extension

4 9:45 How Changes in the Farm Bill May Impact Your Business, Erin Roche, University of Maine. 10:00 Using the DA meter to measure fruit ripeness and to solve Honeycrisp storage problems, Larry Lutz, apple grower and Director of Grower Services for Scotian Gold cooperative in Nova Scotia. (Info on DA Meter at 10:30 Break 10:45 Making your farm safe for visitors and employees, Jorge Acero, Maine Dept. of Labor. 11:15 Maine State Pomological Society Business Meeting, Andy Ricker, President. Legislative Update, State Senator Jim Dill and Representative Jeff Timberlake Noon Lunch - Grilled burgers and chicken, salads, dessert 1:00 3:00 pm Tree Fruit Tour Special guests Larry Lutz, Scotian Gold and Jorge Acero, Dept.of Labor. Also Glen Koehler and Renae Moran. Strategies for controlling bitter pit in Honeycrisp, the new tall spindle apple orchard, cold hardy plum varieties, and ladder safety. 1:00 3:00 pm Berry and Vegetable Tour David Handley and Mark Hutton. Pumpkin, sweet corn, broccoli, raspberry variety trials; pest update; and high tunnel tomatoes, irrigation and compost application in high tunnels. ***Make checks payable to the University of Maine Cooperative Extension. If you are a person with a disability and will need any accommodations to participate in this program, please call Pam St. Peter at the Highmoor Farm at (207) or TDD to discuss your needs at least 7 days prior to this event. The Highmoor Farm thanks the generous sponsors for this event. Crop Production Services, Randy Drown Northeast Ag. Sales, Inc., Paul Peters Directions to Highmoor Farm, 52 US Route 202, Monmouth, Maine Traveling North on I-95: Drive north on the Maine Turnpike (I-95) and take Exit 86 in Sabattus. Turn left onto Route 9/Middle Road. Travel about 2 miles on Route 9 East, then turn left onto Route 132. After 4.5 miles, turn left onto Leeds Junction Road. Travel about 2.8 miles, then turn right onto Route 202 and travel about 1.3 miles up the road until you see Highmoor Farm on the right. Traveling South on I-95: Take Exit 109B in Augusta. Continue west on U.S. Route 202 and travel about 15 miles. Highmoor Farm will be on the left.

5 Closing Words.. When somebody tells me they are absolutely certain about something, I doubt them ~ Karl Koehler Glen W. Koehler Associate Scientist IPM glen.koehler@maine.edu Voice: (within Maine: ) Pest Management Office, 491 College Avenue Orono, ME Dr. Renae Moran Extension Tree Fruit Specialist rmoran@maine.edu Voice: ext. 105 Highmoor Farm Ag. Exp. Station, P.O. Box 179 Monmouth ME Putting Knowledge to Work with the People of Maine Where brand names are used, no endorsement is implied nor is any discrimination intended against products with similar ingredients. Always consult product label for rates, application instructions, and safety precautions. Users of these products assume all associated risks. The University of Maine does not discriminate on the grounds of race, color, religion, sex, sexual orientation, including transgender status and gender expression, national origin, citizenship status, age, disability, genetic information or veteran status in employment, education, and all other programs and activities. The following person has been designated to handle inquiries regarding non-discrimination policies: Director, Office of Equal Opportunity, 101 North Stevens Hall, If you are a person with a disability and need an accommodation to participate in a program described in this publication please call Glen Koehler at or glen.koehler@maine.edu to discuss your needs. Receiving requests for accommodations at least 10 days before the program provides a reasonable amount of time to meet the request, however all requests will be considered.

Maine Tree Fruit Newsletter

Thursday, May 28, 2015. Vol. 23:11 Maine Tree Fruit Newsletter Apple Scab.. Many Maine orchard locations received at least some rain on Thursday May 28. For some locations it was just a sprinkle but for