MSU Extension

Weather report

The Aug. 2 storms caused variable yet extensive damage to fruit crops across the region; these storms also caused considerable damage to homes, roads and trees in many towns in the area. Many homes and businesses, including the Northwest Michigan Horticulture Research Center (NWMHRC), are still without power. The Sunday storms came in three waves, each bringing high winds, heavy rains and some hail. Reports of hail damage are extensive in some areas, and the apples at the NWMHRC have considerable hail damage. We have grower reports of hail damage so extensive that fruit browned on trees 10 minutes after the hail moved through the orchard. Nickel- to quarter-size hail has been reported in many locations. Apple orchards in the northern and southern parts of the northwest region are not reporting hail damage.

High winds resulted in fruit being blown off trees, and some of the tart cherry crop came down with these winds. If the wind did not knock cherries off the tree, fruit was damaged by the high winds. However, quality still remains decent as of today, Aug. 4, and growers are hurrying to remove fruit from trees before quality declines. High winds also knocked down high-density apple trellises in a few orchards; apples were also blown from trees in some locations.

Crop report

Many grape vineyards in Grand Traverse and Leelanau counties were hard hit by storms on Sunday. We have not yet heard if there was damage in Benzie County or Antrim County vineyards. High winds – some gusts of 70 miles per hour recorded in the region – and large hail tattered leaves and smashed the windward side of berries. There was a good deal of injury to shoots and cluster stems, so we may continue to see losses from this storm for some time.

Hail injury can be quite variable within a vineyard. Michigan State University Extension highly recommends walking every row to accurately assess the level of injury. Data and photos are advisable in case of crop insurance claims down the road.

There is a significant threat for Botrytis to infect the storm-injured tissues, making matters much worse. MSU plant pathologist Annemiek Schilder recommends treatment for Botrytis as soon as possible in vineyards that experienced injury. She thinks Luna Tranquility is probably the best bet, used at 16-24 fluid ounces (higher rate for more back action) with a light rate of non-ionic surfactant for better coverage. Other options are Rovral, Endura, Vangard, Scala, Switch and Elevate. Schilder is working on an article regarding the storm injury and disease threat to be released through MSU Extension News for Fruit very soon.

We are still gathering information on the damage to the remaining fruit crops in the region. Sweet cherry harvest was mostly finished, so thankfully we avoided any damage to those crops. As mentioned above, high winds knocked tart cherries off trees; Balatons seem to be particularly hard hit. We expect to see more bruising show up in tart cherries with the high winds from Sunday. We have heard reports of hail damage in tart cherries as well. Hail damage is evident in many apple blocks including apples here at the NWMHRC. We will continue to assess the damage to the region’s crops in the coming week.

Pest report

Some apple growers are applying streptomycin in areas where high winds and hail damaged fire blight-susceptible apple varieties, and apple orchards with hail damage need a streptomycin application as soon possible. Tissue, especially shredded leaves, that was damaged by wind or hail are points where the fire blight bacteria can enter and cause infection. Streptomycin applied within 24-48 hours after the storm should minimize the potential for a fire blight infection. Copper is another option that should reduce fire blight infection; copper should only be used in blocks where fruit finish is not a concern.

Where grape clusters were damaged by hail, growers should prevent Botrytis infection. We have had reports of 10-30 percent infection in 100 percent of clusters in some vineyards that were hit by hail in Leelanau County. Locally systemic fungicides will provide good control of botrytis.

Spotted wing Drosophila (SWD) catches have risen quickly in the northwest with trap catches doubling last week. We encourage growers to continue protecting blocks they have not yet harvested and are still planning to harvest to prevent SWD larvae in fruit. Growers should use tight intervals between SWD sprays (seven to 10 days with full covers) to keep fruit protected. We have had reports of larvae in fruit that have been treated organically as well as in orchards where spray intervals have been stretched out to 14 or more days. Based on evidence from SWD trials this season, growers should not rely on Imidan stretched to 14 days to keep fruit protected from SWD infestation.

Overall, insect activity has decreased in the trap line at the research station. However, cherry fruit fly activity is ongoing throughout the region, and growers should consider a post-harvest insecticide targeting cherry fruit flies to knock back the population for next season. We are continuing to see apple maggot adult activity on ammonium-baited sticky traps at the NWMHRC. We did not detect codling moths this week, and spotted tentiform leafminer activity is also lower with an average of 75 adults per trap this week. Obliquebanded leafroller flight is also lower this week and larvae have been found in apple terminals. We found eight American plum borer moths per trap, 10 lesser peachtree borer moths per trap and four greater peachtree borer moths per traps in pheromone-baited delta traps.

Michigan wine grape winter injury survey

Grand Traverse region grape growers were mailed a survey form in July asking for site-specific information on winter injuries experienced in 2014-2015. If you did not get one, it most likely means we do not have current address information for you. If you would like to participate in this survey, please contact Duke Elsner at elsner@msu.edu and arrange for a survey form to be sent to you. We need to get the survey completed and returned to MSU Extension by Aug. 10.