Northern Michigan FRUITNET'99
Weather: The season continues to be very wet, with 0.95" of rain this past week at the NWMHRS. A storm with high winds hit the area on July 31, with highest winds in the Northport vicinity. Since June 28 at the NWMHRS we have recorded 10.27", with precipitation being recorded on 24 of 43 days! It can't get much better than this for growing most agricultural crops, as well as most fungal diseases!
Growing Degree Days:
INSECTS & DISEASES
Tart cherry harvest concluded last week. Tart cherry growers hopefully applied a post harvest application of Bravo. Growers with cherry leaf spot problems should consider two post-harvest sprays, due to a combination of the early harvest, amount of rain, and multiple infection periods. Leaf spot continues to show up in sweet cherries where no post harvest applications were made. Most sweet cherries should receive a post-harvest treatment.
In plums, apple maggot may need control this year. Pressure is heavy; high trap catches are reported. Brown rot pressure in plums is also higher than in recent years.
Peaches have a high incidence of split pits this year, as a result of the environmental conditions that we have had this season. Rapid growth at the time of pit formation causes the fruit to have a split pit. Light crops, with large fruit, will also increase the incidence, as will the genetics of the variety. Red Haven is one variety prone to split pit. Brown rot pressure is high.
Apples are sizing well. Apple maggot adults continue to move into commercial apple orchards. Moist conditions have allowed for constant emergence of this pest. Codling moth trap catches rose only slightly this week. I don't believe we have seen the peak flight for the second generation yet. Many apple orchards have excellent biological control of mites so far. Mite predators have been plentiful this season. Potato leaf hoppers continue to infest young apples. Guthion and Imidan are the two best controls for this pest. Provado will only control them for a short time. Potato leaf hopper injury should be dissipating quickly as terminal buds set. Spotted tentiform leafminer adult trap catches remained high this week. Tissue feeding mines from this generation are present and more will likely show up due to high adult catches. Growers with an average of 2 mines or more per leaf or more should consider an application of Provado to prevent additional mines from showing up.
Leaf Sample Window Closing
The nutritional health of tree fruits is best assessed by measuring the concentration of nutrients in plant parts. These nutrient concentrations are a direct measure of the nutritional status of the crop. In contrast, soil tests only estimate the ability of soils to supply nutrients and may not predict actual nutrient levels in the crop.
The window for sampling leaves for tissue analysis is closing towards the middle of this month. Leaf samples are best collected during July through mid August. The sampling procedure is fairly easy. Simply collect 100 leaves that are fully expanded and from the middle of the current season's growth. Do not sample spur leaves or leaves damaged by insects, disease, wind or abrasion. Remove the leaves by pulling down toward the base of the shoot so that the stem remains on the leaf. If a strip of bark remains attached to the leaf, it is most likely too early to do leaf sampling. Collect leaves from as many different plants as possible throughout the variety or sampling area. Use leaves that can be reached from the ground from all sides of the tree. Once collected, simply lay the leaves out on a sheet of paper and allow them to dry. Once dry they can be placed in a paper bag with some holes punched along the edges so the leaves will continue to dry and not mold.
Leaf samples can then either be sent directly to the lab at MSU or taken to your local Extension Office. The address for the lab is: MSU Soil Testing Laboratory, Plant and Soil Science Building, Michigan State University, East Lansing, MI 48824. Please pre-pay with a check for $20.00 for each sample, payable to Michigan State University. Samples taken to the County Office need the same procedure. Please also include the variety of the sample and the age of the tree.
Please call your local Extension Office or the NW MI Horticultural Research Station to request the appropriate form to enclose with your sample.
The NW MI Horticultural Research Station Open House and Equipment Show will be held on Thursday, Sept. 2nd. The equipment display area will open at 1:00 p.m. There will be a program from 2:15 until 3:00 p.m. to commemorate the 20th anniversary of the Research Station. Sprayer demonstrations will begin at 3:45 p.m. A social time, beginning at 5:30 will be followed at 6:30 by a pig roast, sponsored by the Leelanau County Horticultural Society. Tickets for the pig roast will be available at the door for $15. The evening will conclude with a short program conducted by the Leelanau Horticultural Society. Everyone is invited to attend!
Answers To Questions About Sovran and Cherries
In experimental trials conducted in the United States between 1996 and 1998, Sovran® fungicide (a.i. – kresoxim methyl) has demonstrated excellent activity against cherry powdery mildew and cherry leaf spot. These studies were conducted on Bing and Montmorency cherries. No phytotoxicity was observed in any of these trials.
There were some instances of phytotoxic symptoms on a relatively small number of sweet cherry varieties such as Van, Sweetheart and Summit in Europe after exposure to kresoxim-methyl. These observations were made on cherry varieties that were sprayed directly; symptoms were less pronounced when sensitive cherry varieties were exposed to drift. There are no indications that spray tank contamination with Sovran has caused injury on cherries. BASF is in the process of investigating the crop safety of Sovran on cherry varieties in the U.S. in controlled phytotoxicity trials.
Preliminary results from these studies confirmed previous observations that numerous U.S. varieties had no phytotoxicity problems. These varieties included: Bing, Brooks, Cashmere, Gold, Hardy Giant, Hartland, Hedelfingen, Hudson,
Kristin, Lapins, Lambert, LJ 436, Montmorency, Napoleon, Nelson Black Sweet, Rainier, Royal Ann, Sam, Stark Crimson, Stella, Sue, Tehranivee, Tulare, Ulster, Vega, Vic, Viscount, Windsor.
The following varieties showed minor to moderate phytotoxicity following application of Sovran at the highest proposed label rates: Cavalier, Coral Champagne, Emperor Francis, Royalton, Schmidt, Summit, Viva.
The following varieties showed severe phytotoxicity following application of Sovran at the highest proposed label rates: Somerset, Sweetheart, Valera, Van, Vandalay. These varieties may also be injured by spray drift containing Sovran.
On all sensitive varieties the injury manifested itself as leaf burning. Affected trees resumed growth and produced normal foliage after exposure to Sovran. As leaves matured, they became less sensitive to Sovran. Fruit injury by Sovran has not been observed in any trial in any variety tested, including those varieties that showed leaf burn.
Supporting studies indicated that the injury risk from spray equipment used to spray Sovran was negligible when spray equipment was thoroughly cleaned prior to using it on sensitive cherry varieties.
Based on the results to date, BASF recommends the following use directions in areas where cherries are grown:
Sovran is a registered trademark of BASF Corporation
©1999 BASF Corporation
NW Michigan Horticultural
Growing Degree Day Accumulations for July 10 - Aug. 9, 1999
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