Southwest Michigan fruit update – Aug. 14, 2018

Mild, sunny conditions help move peach and plum ripening.


Temperatures last week ranged from lows in the mid-60s and highs in the mid-80s. Several rains over the past week totaled approximately one-third of an inch. We continue to be about two weeks ahead of normal.

Southwest Michigan GDD summary from March 1 – Aug. 5, 2018


GDD 42 F

GDD 45 F

GDD 50 F

Benton Harbor (SWMRC)




Lawton (Lawton)




Fennville (TNRC)




Average for the SW region




Accumulation last week




Tree fruit

The southwest Michigan region has had more rainfall over the past three months compared to the other Michigan fruit growing areas to the north and east. This has led to more concerns and problems with mid-summer diseases such as brown rot of peaches and fruit rots of apple.

San Jose scale trap catches continue to be high for the fourth straight week. Apple maggot numbers have been high for four weeks. Insecticide choices should include materials effective against apple maggot. Brown marmorated stink bug adults from the summer generation are starting to become more common, with damage to fruit becoming more common. Spotted wing Drosophila numbers continue to climb.

Peach and nectarine harvest of Redhaven, PF Lucky 13, Starfire and some John Boy is underway in central Berrien County. Rainfall has been adequate for good sizing and flavor has been good. Fruit scab is more prevalent this year due to frequent rainfall. The exaggerated sutures reported last week and non-aborted fruit remnant often associated with these deep sutures can be a place where brown rot problems start. Fungicide treatments for brown rot are needed as fruit background color loses its green color. Leaf drop of older leaves due to bacterial spot infection is common on susceptible varieties.

Oriental fruit moth numbers are up this week compared to last week. This is the third generation flight. Growers who deployed pheromone disruption for oriental fruit moth starting at or shortly after bloom may see increased pressure from this insect as the lures start to wear out. Sprayable pheromones are available to extend the period of control. Peaches are especially attractive to brown marmorated stink bugs, causing white regions of slightly firmer, disorganized peach flesh close to the skin.

Loss of cherry leaves due to cherry leaf spot continues in area orchards. Maintain fungicide protection to preserve the remaining leaves. August is a common time to see slight wilting, drought-like symptoms of tart cherry trees infested with the brown American plum borer larvae in the crown area.

Plum harvest of Vanier, Ozark Premier and Redheart is ongoing. Continue protecting against brown rot. Ripening plums should be protected against apple maggot. Apple maggot numbers continue to be high for the traps at the Trevor Nichols Research Center. Codling moth and oriental fruit moth can also attack plums. Spotted wing Drosophila can attack plums as they ripened, with their thin skins and soft flesh. Plums become susceptible when they soften to approximately 3 pounds of firmness, measured without skin. Use a fruit firmness gauge fitted with a pear tip.

In apples, spot-picking of Zestar has started in a few area orchards. Color is improving for Gala, but starch and firmness tests show this variety has a long way to go before it is mature. Frequent rains have prompted growers to renew fungicide coverage necessary for controlling sooty blotch and fly speck.

Catches of oriental fruit moth and codling moth adults continue at relatively low levels in some orchards. At this point, we should be in the third generation flight of oriental fruit moth and the second generation of codling moth. The second generation of obliquebanded leafroller is also flying and egg hatch has begun in some orchards. Apple maggot numbers continue to be high. Insecticide choices should include materials effective against apple maggot.

Necrotic leaf blotch symptoms are showing up in Golden Delicious. Necrotic leaf blotch appears in Golden Delicious and other apple varieties with Golden Delicious as a parent, such as Gala. Affected leaves have yellow, green and dead blotches and fall from the tree. These symptoms usually occur following a rain, which ended a long and dry period.

Pears become attractive to codling moth attack when they soften close to harvest in August. Pears need to be protected from the second generation flight, which is occurring now.

Small fruit

Grapes are in veraison. Berries are softening and coloring. Scout for powdery mildew and downy mildew on the leaves. Downy mildew will be a problem as heavy morning dews become common. The leaves of susceptible varieties should be protected.

Egglaying of the third generation of grape berry moth is continuing. Few moths are being trapped. Most of the damage we saw in the vineyards was left over from the second generation. Check vineyards and consider whether to take additional action to control the third generation. Insecticides with good contact activity are the best options for this tactic. You may be able to use border sprays, as the damage is concentrated on vineyard borders adjacent to woods that contain wild grape.

The number of spotted wing Drosophila flies in traps is still increasing, and now that veraison is rapidly approaching, check vineyards regularly to decide whether treatment is needed for spotted wing Drosophila and other native vinegar flies that infest ripe clusters. Here again, border sprays might be an option for vineyards with rows parallel to woods.

We are starting to see brown marmorated stink bugs in some vineyards, and there are reports of increasing brown marmorated stink bug numbers in other crops in southwest Michigan. Look for this insect until harvest. A clean-up spray using a contact insecticide with a short pre-harvest interval may be required to knock down brown marmorated stink bugs from clusters before harvest.

Very few Japanese beetles were found, and overall the numbers are still low. No other insect issues were found during scouting.

Blueberry harvest is winding down with Jersey and Elliott. Harvest is moving quickly. Many growers report they will be finished early due to low yields in Elliott. Growers are applying fungicides and insecticides to protect ripening fruit against fruit rots and spotted wing Drosophila. Spotted wing Drosophila numbers are high. Maintain irrigation to maintain bush health and set the plants up to set a good crop of flower buds for next year. During the summer, blueberry fields need an inch of water every three or four days.

Strawberry leaves should be protected from leaf diseases and potato leafhoppers, which stunt plant growth. Maintain irrigation.

Bramble harvest continues. Fall raspberry harvest is underway. Raspberries are a preferred host for spotted wing Drosophila and the fruit always needs to be protected.

Upcoming meetings

The annual Trevor Nichols Research Center Field Day is Tuesday, Sept. 25, 2018, from 1 to 4 p.m. at the Trevor Nichols Research Center, 6237 124th Avenue Fennville, MI 49408.

Did you find this article useful?

You Might Also Be Interested In