MSU Extension Fruit & Nuts

Weather

The last two weeks have been a real weather rollercoaster. Two weeks ago we had highs in the 90s. The following week was cool and wet, with highs in the 70s. Last week began with dry weekend followed by a wet Tuesday and Wednesday. Rainfall totals for the week, averaged about an inch and ranged from 2/3 to 1.5 inches. High temperatures rose from the 70s into the 80s. The weekend was very hot with highs in the 90s and lows in the 70s indicating a high dew point and very moist air. The passage of a cold front Sunday night dropped temperatures 20 F. Soils are wet. Some areas of Southwest Michigan have received about 5 inches of rain more than the evaporative demand of the plants, which are using about 0.2 inches of water a day. Hot weather will return this week. While March and April were relatively cool, May and June were much warmer than normal. Our heat accumulation were about two weeks behind normal in late April and we are now about two weeks ahead of average. We are about 10 days ahead of our normal heat accumulation.

Southwest Michigan GDD Summary from Mar. 1 through July 1, 2018

Tree fruit

Plant growth has been good due to abundant rain in the area. San Jose scales are appearing on fruit from the first generation. Japanese beetle adults are emerging from now and into July after rain events. Brown Marmorated Stink Bug juveniles are still relatively hard to find. They are expected to mature into flying adults starting in late July. Wild berries such as mulberry and bush honeysuckle are ripening providing a nursery for spotted wing drosophila (SWD). SWD numbers continue to increase. More traps are catching flies and numbers are increasing in traps that are catching flies. Traps near strawberries and wild ripe fruit are catching a lot of flies. This hot weather is hotter than SWD likes and will increase the time it takes to reproduce between generations. See: Plan to change when dealing with spotted wing Drosophila. Also see the Spotted Wing Drosophila website for much more information on SWD

Apricot harvest began last week for the early varieties. Fruit are relatively free of bacterial spot symptoms.

Peach and nectarine hand thinning is winding up. Estimated peach harvest dates are available on Enviroweather. Redhaven harvest is projected to begin about August 1^st. The fruit of the first variety of the season, Rich May, are fully colored and are firm ripe with Desiree and PF1 to start soon. Fungicide treatment for brown rot are needed as fruit background starts to lose its green color. Yellowing leaves due to bacterial spot is evident for susceptible varieties. The oriental fruit moth second generation flight should be underway. Branch end flagging and fruit entries by first generation oriental fruit moth larvae are common at some sites.

In Cherries, harvest of mid-season sweet cherries has begun. Montmorency tart cherry harvest will begin in earnest after July 4. SWD trap catches in the Southwest region are increasing especially near crops and wild plants with ripe fruit. Trap catches in some cherry orchards have also increased. Growers need to maintain insecticide coverage for SWD until they finish harvest. See: Managing Spotted Wing Drosophila in Michigan Cherry. Yellow leaves caused by cherry leaf spot or bacterial canker are common in area orchards. Cherry leaves are always susceptible to cherry leaf spot infection and need to be protected until after harvest to preserve the leaves. Ripening cherries are very susceptible to brown rot.

This tart cherry orchard has been almost entirely defoliated by cherry leaf spot. Without leaves, it will be impossible to mature and harvest the fruit.

Cherry leaf spot usually begins in the tops of the trees where the spray coverage is the poorest. 

Plum fruit should be protected against apple maggot. Codling moth and oriental fruit moth will also attack plums. SWD can also be a problem in plums as they ripened. Plums become susceptible when they soften to approximately 3 lb. firmness, measured without skin, using a fruit firmness gauge fitted with a pear tip. Brown rot also becomes a threat as fruit start to ripen, color and soften.

Apple hand thinning is done for most orchards. Fruit entries by oriental fruit moth and codling moth larvae began appearing about two weeks ago. Codling moth trap catch numbers are low indicating the end of the first generation flights. The second flight of oriental fruit moth should begin soon. Oblique banded leaf roller first summer moth catch (biofix) was June 8, with egg hatch estimated to have started June 20. Growers should scout for larvae feeding on the foliage. Apple maggot have been caught in the area for two weeks. Apple maggot is a summer pest which emerges following rains. Fire blight is a problem in only a few area orchards. Sooty blotch and fly speck symptoms are expected in most of SW. Higher, exposed sites such as the SW Michigan and Trevor Nichols Research Centers have fewer wetting hours and less risk due to these diseases so far. 

Southwest Michigan Sooty Blotch and Flyspeck Model Output as of July 2, 2018. The model is initiated 10 days past estimated petal fall for the location. Days with a minimum of 4 hours continuous wetness are included. First symptoms are expected at 240 to 290 wet hours.

Pear fruit are growing rapidly and will become attractive to codling moth attack as they soften close to harvest. Pear psylla numbers are relatively low. Hand pulling of water sprouts will help to discourage psylla building up. Early season fungicide treatment for pear scab will prevent initial infection by Fabraea. Once the pear scab season has passed, continued fungicide treatment for Fabraea leaf spot may be required in wet seasons if the disease has been established on leaves.

Small fruit

In Grapes, most varieties are nearing berry touch. Black rot on the fruit and phomopsis on the stems are easy to find. We are nearing the end of the critical post bloom period for the controlling diseases on grape such as powdery mildew, downy mildew, phomopsis, and black rot. Botrytis appears to be fairly common in the berry clusters and growers should include fungicides with good action against botrytis in the next fungicide sprays before the berries touch and the cluster tightens. See: Controlling Botrytis bunch rot in grapes. Grape berry moth flight is down. We are seeing fresh stings in berries. The flight of the second generation is being. Most growers should spray to control this generation and the third generation close to harvest. See: Using the MSU Enviroweather grape berry moth model in 2018. Japanese beetles are scarce. Grape and potato leafhopper numbers are low. Brown Marmorated Stink Bug numbers remain low. There is no need to spray for SWD in grapes until after veraison.

The dark remains of botrytis infected berries inside this grape cluster can start a botrytis infection later in the year. 

Blueberries ripened quickly in the heat. Harvest of early varieties is well underway. The hot weather caused some sunburn in ripening fruit and drought stress burning of the leaves as the bush has a hard time cooling itself in the hot humid conditions. The plants do fine when it is 70 F and overcast for a week, but 4 days of hot sunny weather with highs in the 90s and a heat index over 100 literally cook exposed leaves and fruit in the heat. Growers are applying fungicides and insecticides to protect ripening fruit against rots and SWD. See: SWD in blueberry recommendations in English. Generally the frequent sprays required to control SWD are equally effective against blueberry maggot. Blueberry stem galls are becoming easy to find. This is not a major pest in the southern growing region of Michigan.

These duke berries were literally cooked in the hot sun over the weekend. Growers report finding only a small percentage (one-to-five percent) of affected fruit. 

Strawberry are being renovated.

Brambles fruit are coloring. Red raspberry harvest is begun and black raspberry harvest will begin soon. Blackberries are still green. Japanese Beetles are out and more should emerge after summer rains into August. Target Japanese beetle as soon as you see it to prevent this pest from aggregating in your fields. SWD traps should be out to monitor this pest. Raspberries and blackberries are a preferred host for SWD. We are beginning to catch SWD in the Southwest region with a few traps showing a dramatic surge in number near wild hosts with ripe fruit. See: SWD recommendations for raspberries and blackberries. We are seeing floricane collapse. This may be due to winter injury or an anthracnose infection last year. Anthracnose is easy to find in wild black raspberries.

Cranberry bloom continues.

Current berries are ripening and these berries need to be protected from SWD.

Upcoming meetings

The Michigan Grape Society is hosting a Grower social.

Related articles:

• Plan to change when dealing with spotted wing Drosophila
• See the Michigan State University Spotted Wing Drosophila website for much more information on SWD
• Control of American brown rot
• Cherry leaf spot 101: Understanding Blumeriella jaapii biology and management
• Banning black rot and Phomopsis from young grape clusters
• Early season vineyard disease management.
• Using the MSU Enviroweather grape berry moth model in 2018
• Anthracnose fruit rot prediction model to assess risk of infection in blueberries
• Blueberry weed control: late spring and summer options
• Strawberry renovation is due soon.