MSU Extension

Weather Report

Although the region has been particularly dry so far this season, the weekend kicked off to a hot and humid start. Most of the area received some rainfall on Friday night into Saturday morning (June 9-10) and many Enviro-weather stations in the region recorded almost .5 inches of rain; Eastport recorded over one inch of rain while Northport and the Northwest Michigan Horticultural Research Center (NWMHRC) received less than half of one inch. Following the rainstorm on Friday evening, we hit the mid-80s on Saturday, and by Sunday, June 12, temperatures cooled off and the humidity dropped. Temperatures for the coming week are predicted to be in the low to mid-70s, and we will hit the low 80s over the weekend. There is rain in the forecast for Wednesday and Thursday with a potential thunderstorm on Wednesday, June 15.

Crop Report

Sweet cherries are sizing at the research station, and the fruit is in the 11 to 14 millimeter range. Some of the fruit in the sweet cherry variety trial is starting to color, and these fruit are straw colored and some are starting to show a pink blush.

Tart cherries are also sizing, and the crop size looks quite large across northwest Michigan. The estimates on crop size are variable, but the general opinion is that the crop size is pretty big.

The apple crop is also sizing, and growers were challenged with thinning this season. We moved so quickly at the beginning of bloom to the first fruitlets starting to size, so many growers were unable to take advantage of the nibble thinning approach. Additionally, the weather turned cool late last week, which made thinning more challenging, particularly as fruit is upward towards 20 millimeter in size. There will likely be hand thinning taking place in many apple blocks.

We are approaching the pre-bloom stage for many wine grape varieties. I have now seen some vinifera that appear to have “stalled” shoot growth, stuck at 6 to 8 inches in length while nearby plants have shots twice that length. The canes bearing the short shoots were not severely injured by the 2015 hail storm, but the vines in this location had suffered badly from the cold injuries of the 2014 and 2015 winters.

No symptoms of powdery mildew have been reported, but we are entering the pre-bloom and bloom period which is a critical period for protecting vines from powdery mildew infections. Rose chafers are the only significant insect activity at this time. The numbers are variable but a few hot spots have been reported. At low populations they typically feed on the foliage and their injury can be tolerated (except on first and second year vines) but at high populations they sometimes feed on flower clusters and controls may be warranted.

Saskatoon berries are starting to show some red coloration. However, if only one of two berries in a fruit cluster are showing a lot of red color, they are likely to be infested with saskatoon sawfly or apple curculio larvae. Apple curculio were still depositing a few eggs during the last week in the unsprayed saskatoons at the research center. The activity of leaf-curling aphids has picked up a bit. Protecting berries from rust infections is the main disease concern now, and growers need to be aware of the long pre-harvest intervals for certain fungicides. It is too late to use Tilt or Quilt Xcel as these have a 30 day PHI.

2016 Growth Stages as of 6/13/16

• Bartlett Pear – 16 millimeter fruit
• Potomac Pear – 21 millimeter fruit
• Mac – 16 millimeter fruit
• Gala – 17 millimeter fruit
• Red Delicious – 20 millimeter fruit
• HoneyCrisp – 19 millimeter fruit
• Montmorency – 11 millimeter fruit
• Balaton – 13 millimeter fruit
• Hedlfingen – 14 millimeter fruit
• Gold – 11 millimeter fruit
• Napolean – 12 millimeter fruit
• Riesling – 10-16 inch shoots

Pest Report

Fire blight symptoms began showing up in northwest Michigan orchards last week and this week, symptoms are becoming more apparent in orchards. We have received several reports of fire blight throughout Northwest Michigan; we could have more reports in the coming days as symptoms become more visible. MSU Extension is collecting fire blight samples to screen for bactericide resistance and we encourage growers to contact the NWMHRC if they have fire blight infected trees.

Several consecutive days with warm temperatures in the upper 70s and into the 80s during bloom were optimal conditions for fire blight growth on flowers. Additionally, this bloom-time weather was ideal for pollination meaning that bees also readily spread the high population of fire blight bacteria throughout orchards. Epiphytic Infection Potential values reported on Enviro-weather were very high with some areas at values of 300+ during bloom. Under these conditions, the fire blight model predicted that retreatment was needed one or two days after a spray in some cases. However, restrictions on reapplication intervals of some materials was a limiting factor that could have contributed to bacteria build up on flowers during bloom. These conditions were the perfect storm for fire blight this season and symptoms are present even in orchards with rigorous fire blight programs. We have observed ooze on terminals which contains fire blight bacteria that can be spread during rain, and this ooze is a concern for possible trauma blight. Damage (hail, high winds, pruning cuts, etc.) to leaves, limbs and trees that make open wounds are areas where fire blight can enter and infect a tree.

Growers that have fire blight will need to slow its spread until trees reach terminal bud set and growth is inhibited. Copper sprays can kill the bacteria, but there is also the potential for fruit russeting and phytotoxicity on foliage, particularly if it is applied in high temperatures in the 80s and high humidity. Growers on the Fruit Ridge have had fewer fruit finish problems using the copper product Badge; we do not have data to support this observation. Growers who have used Apogee or Kudos this season should continue these programs as these materials will continue to slow terminal growth and thicken cell walls thereby preventing further spread of the fire blight bacteria inside of the tree. If Apogee or Kudos has not been used this season and terminals are 6 inches or longer, these materials will likely have little impact on fire blight spread at this time. In orchards with low incidence, infected terminals can be removed and orchards that are pruned should be treated before rain to prevent bacteria from being washed into pruning wounds. Some growers also use low water volumes to allow faster drying time to have quicker activity against the bacteria; however, we do not have scientific data to support this either. Pruning out infected tissue may not be feasible in orchards with severe infections and or on smaller trees where pruning would remove a significant amount of the tree. These orchards should be treated to kill the bacteria to help prevent the spread of bacteria. There is the possibility of heavy rains overnight tonight into Wednesday and or on Wednesday. Thunderstorms are also predicted with a possibility for additional rain on Thursday. These conditions are a concern for trauma blight and growers with existing fire blight symptoms should take action before this weather to reduce inoculum that could be the source of trauma blight.

The end of the primary phase of apple scab could be near in orchards that had low inoculum going into the season. Overall apple scab incidence is low, but growers and consultants should continue to check for scab lesions on fruit and leaves. According to the NWMHRC biofix (April 17), 100 percent of scab spores are mature and 95 percent have discharged at this time. There have been low levels of spore discharge in recent rain. However, these rains have either been overnight (Friday, June 9) or very light (.01 inch on June 13) which could have resulted in a lower discharge. Possible afternoon rain on Wednesday and Thursday will be a better indicator of ongoing spore release.

Cherry leaf spot incidence remains low throughout the region. Symptoms from the long infection period (June 4-June 6) that swept through much of the region could begin appearing this week if infection occurred. Heavy rains on Friday night likely washed fungicides from leaves, and reapplication will be needed prior to the next possible rains to protect foliage from leaf spot. Several growers used a Gem + Captan or an SDHI for their first cover spray to target both leaf spot and powdery mildew. We remind growers to check labels and rotate fungicide groups according to the label. There is some concern among growers of having too few leaf spot materials to rotate in sweet cherry, in particular a material that is not a group seven or 11 fungicide. Captan alone is rated good/excellent for leaf spot and is not in the fungicide group seven or 11.

Spotted wing drosophila were not detected in northwest Michigan last week; the first spotted wing drosophila was detected on Friday, June 3, in Northwest Michigan. Green cherries are not susceptible to spotted wing drosophila egg laying; growers should wait until fruit begin turning color and spotted wing drosophila are detected on-farm, in an neighboring orchard, or when 5-10 percent of regional traps catch this pest to begin management. The NWMHRC has deployed traps in strawberry to monitor for this pest and we will continue to provide trap catch updates on Fridays to FruitNet subscribers.

Cherry fruit fly traps are up and we have not detected fruit fly at the station. There has been a lot of attention shifted toward spotted wing drosophila this season; we encourage growers and consultants to begin planning management strategies that will provide efficacy for the complex of late season pests: spotted wing drosophila, cherry fruit fly, and if needed, obliquebanded leafroller. Additionally, mites have typically been a concern after harvest. However, an overall drier season and pyrethroid use for late season pests could contribute to higher than usual mite populations

According to the Enviro-weather codling moth model, we have accumulated about 261 GDD base 50 degrees Fahrenheit since our biofix (May 26) and codling moth egg hatch is ongoing. In orchards that have reached the codling moth threshold and have accumulated about 250 GDD base 50, treatment may be needed if an ovicide was not applied. In orchards with codling moth captures below threshold and in orchards that treated for eggs, delayed treatment at about 350 GDD base 50 is an option. Peak egg hatch occurs about 500-650 GDD base 50.

American plum borer and lesser peachtree borer catches are down this week and peak catch occurred two weeks ago. Some growers have made or are planning to make trunk spray applications targeting American plum and lesser peachtree borer this week. We remind growers that Lorsban can be phytotoxic to sweet cherry foliage and fruit. Greater peachtree borer activity has not yet been detected at the station this season.

Saskatoon grower education tour

Michigan State University Extension and the Saskatoon Berry Institute of North America are hosting a tour of three saskatoon berry production sites in the Grand Traverse, Michigan, area on Friday, June 17. This event is free, and pre-registration is not required. Participants need to provide their own transportation to the meeting sites.

The tour will begin at 8:15 a.m. at Jacob's Corn Maze, 7100 East Traverse Hwy. (M-72 West), Traverse City, MI 49684. This stop will feature discussions and demonstrations on cultural practices for older plants, pruning methods, pest insects and comparisons of varieties led by Dr. Duke Elsner, Small Fruit Extension Educator for Michigan State University.

At 10 a.m. the tour will arrive at the farm of Jim Dixon in Williamsburg, Michigan, where the care of young bearing plants and fruit marketing opportunities will be discussed. The final stop will be at the Saskatoon Michigan Farm & Nursery, also in Williamsburg, Michigan, at 11 a.m. Owner Steve DuCheney will lead a discussion on tips for planting new stock and caring for young plants.

Participants are invited to meet at Mr. C’s Pub & Grill, 9009 M-72, Williamsburg, MI 49690, to continue their conversations about saskatoon berries over lunch at 12:30 p.m. For further details on the tour contact Steve Ducheney at 231-360-0311, or Duke Elsner at elsner@msu.edu.