Maine Tree Fruit Newsletter

Transcription

1 Wednesday, May 27, Vol. 23:10 Maine Tree Fruit Newsletter Apple Scab.. The final portion of this year s supply of apple scab ascospores will not release until we get some soaking daytime rain over The forecasts show iffy prospects for rain in the coming week. If it rains tonight but the rain does not start until after dark and ends before morning, then that won t change the scab situation, other than to give scab living in overwintered leaves on the ground a supply of moisture to keep them healthy until that soaking rain finally arrives. There is not much known about what happens to scab spores that have to wait a long time before rain arrives, giving them the signal to release. If the lack of rain lasts too long, you might wonder at what point they start dying for lack of moisture. And there is a report (anecdotal at this point until written up for publication) that in dry situations like this, the production of ascospores from last year s leaves is reduced. But it is a moot point because we do not have information to estimate if and how much spore production might be reduced. Moreover, recent spore tests from Belchertown, Massachusetts, where it has been even drier than Maine, have found a substantial number of apparently viable scab ascospores ready to release with the next soaking rain. Belchertown is 10 days past McIntosh 95% Petal fall and growers there are still waiting for release of the bulk the season s primary scab ascospores. The rain on Monday evening into Tuesday morning was too late and too light to cause a full strength infection period. At this point, Maine orchards have only had about 10 30% of the season s total primary scab infection potential. The rest will occur over the next few soaking rainy days. Scab is well engineered to know that a short light night shower that dries off the next morning does not provide long enough wetting for spores to release, land, and grow into leaf tissue before leaves will dry off and kill the spore on the leaf surface. So full release of scab spores occurs during soaking daytime rains. Until that happens, we are still waiting for the end of scab season. The good news in all this is that it gives you opportunity to have protection in place ahead of the next scab infection period. If the on again / off again nature of these spotty rain shower forecasts results in your trees not being protected when the rain arrives, then that is the time to use a material with postinfection activity against apple scab. *** We have several open slots for free resistance testing of scab lesions from your orchard to measure the level of resistance to DMI (sterol inhibitor, strobilurins (e.g. Pristine), dodine, and the recently introduced SDHI fungicides. To participate you just have to leave a corner tree unsprayed, let us collect 50 leaves in June, then you can resume spraying the trees to shut down the scab and prevent spread. Contact Glen at glen.koehler@maine.edu if you would like to have a sample tested. Repeat participants encouraged so that we can compare tests across years from same location.

2 Fire Blight.. Even orchards in southern Maine still had a few open blossoms, meaning that light sprinkles on Tuesday morning would be enough to trigger fire blight blossom infections where inoculum was present. For orchards north of Highmoor, there could be significant fire blight risk this year. It all depends on how many blossoms are still present when rain finally arrives. Unlike apple scab, for fire blight, nighttime rain and just a sprinkle is sufficient to cause full infection intensity. The Wednesday afternoon Cougarblight and Eastern Fire Blight Model risk forecasts are shown below for Appleton. Both models indicate serious infection potential if there is any amount of rain or even heavy dew in the next four days. We do not have a weather site north of Appleton until Fredericton NB, where they just reached King Bloom on Monday May 25, and are having a worst case situation for fire blight weather this week. That suggests that orchards north of Appleton may have even higher risk than shown in the table below. If you have any history of fire blight in or near the orchard, then any blossoms remaining should have receive protective antibiotic before the start of any rain while this unusually warm weather persists. If an infection period starts on unprotected flowers, then you can still apply antibiotic within hours after the start of the infection period to get control. The sooner post infection antibiotic is applied after the infection period started the better. Explanatory text for Appleton Cougarblight table is at radar.umext.maine.edu/memodel/me Appleton FireblightWA.htm Eastern Fire Blight Model (100% = minimum heat threshold for blossom infection)

3 Thinning.. Bloom seems to be heavy in nearly every orchard I have visited this spring, but a few varieties are in the off year. Pollination conditions have been good enough to predict heavy fruit set, but windy sights where bees were sparse may have light fruit set. This year, I am expecting that moderate to aggressive thinning will be needed to reduce the crop to a healthy level. Most of us fear over thinning, but this year we should all be concerned about under thinning. Not thinning enough is costly if you need to hand thin later or if size is reduced. Multiple applications (the nibble approach) of thinners at low doses can sequentially knock fruit off with less risk of over thinning than trying to do it all with one shot. Some of you are trying Duane Greene s nibble approach by starting with Amid thin and following up with NAA or carbaryl, so I am interested in hearing how it works. At Highmoor Farm, we missed the petal fall window and plan to apply a mix of carbaryl and NAA with the rate of NAA adjusted for variety and high temperature. Be cautious with high rates of NAA or 6 BA (Maxcel) when temperatures are predicted to be above 80 F. The long range forecast indicates that temperatures will be warm to hot, so there should be opportunity for thinners to work well this year. However, if the weather continues to be warm and sunny, fruits will rapidly reach a size where they are resistant to thinning. For those of you who predict light fruit set in your orchard, one application of thinner at 7 12 mm may be enough to reduce the cropload. Orchards in northern Maine are probably near full bloom. Amid thin can be applied to apple and pear at the bloom or petal fall stage. It is suggested for thinning for early blooming varieties that are usually thinned with difficulty. A rate of 5 8 ounces per 100 gallons is the effective range with the higher rate for varieties that are difficult to thin, and 4 ounces being too low for effective thinning. If thinners applied at petal fall do not work, you can apply additional thinner when fruit reach a size of 12 mm in diameter. Here is the Wednesday afternoon update of the Monmouth (Highmoor Farm) thinning weather chart.

4 *********************************** Here is the message on thinning and other topics sent May 18 that may not have reached all the people on this list. Fruit Thinning Good pollination is expected for apples, so chemical thinning will be needed to reduce crop load and increase return bloom. At this time, we are near full bloom, but orchards in southern Maine may be near petal fall. Amid-thin can be applied to apple and pear at the petal fall stage. It is suggested for thinning for early blooming varieties that are usually thinned with difficulty. A rate of 4-8 ounces per 100 gallons is the effective range with the higher rate for varieties that are not normally thinned enough. Over the next five days, high temperatures are predicted to be in the upper 60 s F, so chemical thinning will be less effective. If thinners applied at petal fall do not work, you can apply Sevin and/or NAA when fruit reach a size of 12 mm in diameter. Signs of Winter Injury As trees leaf out and bloom, signs of winter injury are becoming more obvious. Peaches have the worst damage, but injury is showing up in plums. Peach flower buds that survived the winter should be in bloom by now in southern Maine. Plums appear to have survived better than peaches, but injury to wood is not as easy to detect as flower bud death. Japanese plums and peaches probably have some injury to their wood, which will not be obvious until mid-summer when temperatures are hot. Look for signs of water stress. If trees have not leafed out yet, they are most likely dead. Since snow cover was deep this winter, there may be shoots arising from below the snow line on trees that look dead. These trees may survive, but will take a few years to replace the branches that have been lost. Most plum are hardier than peaches, but a few Japanese plums are showing winterkill on large branches, particularly Methley which is supposed to be hardy. European plums are hardier than Japanese plums. Some of the hybrid Japanese plums, Toka, Black Ice, Superior, and South Dakota, are the hardiest and show no sign of injury. As for cherries, we have only a few trees, but they are in bloom and look healthy. Fertilizing Fruit Trees The rate of fertilizer needed depends on tree age and soil type. Young trees use less nitrogen than older trees, and dwarf trees use less than semidwarf and standard. Rates of nitrogen by tree size and age are listed in the table below for ground application. These are rates of actual nitrogen and need to be converted to rate of fertilizer. Nitrogen rates in lbs. per tree. Tree age in Semidwarf apple years and pear (250 trees Dwarf apple ( trees / acre) / acre) and older Stone fruit ( trees / acre)

5 Tall spindle orchards where trees are planted 3 to 4 feet in the row can be fertilized in the planting year with 0.04 lbs. nitrogen per tree or up to 40 lbs. per acre, the same rate as dwarf apple. In subsequent years, the rate should be more conservative unless planted in sandy soil. To avoid overfertilizing tall spindle or closely spaced trees, rely on foliar analysis to determine nitrogen needs by the third year. Orchards on fertile loam soil may need only half the listed amount of nitrogen whereas on sandy soil, they may need 50% more. For fertigation systems, rates of nitrogen should be reduced by at least 50%, and should be applied in split applications rather than all at once. A suggested schedule is to split it into three applications beginning at bloom and then at two-week intervals. Fertigation is a more efficient application system and can lead to overfertilization of dwarf fruit trees if the rate of nitrogen is not reduced compared to ground application. Uniform water application is essential to fertigation, so check flow rates on a number of emitters first. Nitrogen content of fertilizers % Nitrogen lbs. of fertilizer to get one lb. of Nitrogen Urea Calcium nitrate Ammonium nitrate Ammonium sulfate Monoammonium phosphate If potassium fertilizer was not added to soil prior to planting, young fruit trees can be fertilized with potassium at a rate of 0.11 lbs. potash / tree. For potassium-magnesium-sulfate fertilizer, this would be 0.5 lb. per tree. On sites that are prone to bitter pit, avoid repeated potassium fertilization until trees reach bearing age. It is best not to exceed 120 lbs. of potash per acre per year in order to maintain a balance with calcium and magnesium. FSA Conservation Form Due June 1.. By June 1, 2015, farmers must file a Highly Erodible Land Conservation and Wetland Conservation Certification form (AD 1026) with the USDA Farm Service Agency (FSA) in order to become or remain eligible for premium subsidy on crop insurance policies in the 2016 reinsurance year (July 1, 2015 to June 30, 2016). Farmers and any affiliated persons must be in compliance with the Highly Erodible Land and Wetland Conservation provisions. Farmers participating in USDA programs such as marketing assistance loans, farm storage facility loans, and disaster assistance may already have a certification form on file. However farmers, such as specialty crop growers who receive federal crop insurance premium support, but may not participate in other USDA programs, must now file a certification form to maintain insurance premium support. Farmers should contact their local FSA office to verify their form is on file. Form AD 1026 is available at local USDA service centers or at the USDA's website at The Maine Risk Management and Crop Insurance Program website is at risk management and crop insurance education program/

6 Closing Words.. Beware the barrenness of a busy life. ~ Socrates Inaction breeds doubt and fear. Action breeds confidence and courage. If you want to conquer fear, do not sit home and think about it. Go out and get busy. ~ Dale Carnegie 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.