MSU Extension Fruit & Nuts

Weather

Soils over much of the region continue to dry out. With another week of hot temperatures, soils continue to lose a good amount of moisture. Signs of drought stress are in newly planted tree and small fruit crops, as well as in shallow rooted fruit crops such as strawberries. Sod in most orchards is turning brown and lanes and driveways are very dusty. It looks more like the dry conditions we would normally see in mid- to late July.

With warm temperatures of the last week, we have seen the rapid growth continue in all of our fruit crops. As a result of another week of warm temperatures, we saw another big jump in growing degree day (GDD) accumulations. Most of our Michigan State University Enviroweather stations have seen a jump of 160 to 170 GDD base 50 accumulations in the last week. Last week, our season moved back to normal to being a few days ahead of normal for both growth stages and GDD.

Tree fruits

Apples have continued to size well over the last week, despite dry soils. Most apple fruit are now 29 to 31 millimeters in diameter. Most apple varieties have between 18 to 22 inches of new terminal growth.

A lingering, long and steady June drop continues in many varieties. Fruitlets continue to drop, although it is hard to distinguish between fruit that is dropping as a result of thinner applications and June drop. Where growers have left check trees, about the same amount of fruit is dropping where thinners were not applied. Most apple growers have a nice apple crop. Hand thinning has not started yet in apples but will be needed in many apple varieties.

I have no new insect pests to report in apples this week. Last week, I reported low numbers of San Jose scale adult males in traps; most farms have biofixed in the past week. Control measures for many of the insecticides used to control it will need to be made soon. Trap catch of obliquebanded leafroller adults continues. European red mite and twospotted spider mites continue to be found in higher numbers, but none are at threshold levels. A few white apple leafhopper adults continue to be found feeding on leaves, as well as a woolly apple aphids and potato leafhoppers. I continue to see a few codling moth larvae. Trap counts of adults are generally low at this time. Beneficial or predator numbers continue to build. I am finding minute pirate bugs, red velvet mites, lady beetles and lacewing adults.

I have no new reports of fire blight strikes. A few more growers are finding cedar apple rust. Apple scab lesions on fruit continue to be found. Some apple blocks continue to have high numbers of powdery mildew infected terminals on mildew prone varieties. Protection programs need to be ongoing on mildew prone varieties.

Pears are mostly 26 to 30 millimeters in size. Most pear growers continue to see some moderate fruit drop in the past week, resulting in a nicely thinned crop with a good crop remaining. Pear psylla adult numbers continue to slowly raise as suckers elongate.

Peaches are between 30 and 38 millimeters in diameter. Thinning continues in some blocks; others will not require thinning due to frost damage. Green peach aphids continue to be found in many peach blocks. Peach leaf curl symptoms are common across the region, but as new leaves develop, the symptoms appear to be diminished.

Sweet cherries, at least those that remain on the tree, have continued to swell and color well in the last week. Most remaining fruit are between 24 and 26 millimeters in diameter and are about seven to 11 days from being ready to harvest. As I have been reporting over the last five weeks, there has been a long, slow but steady amount of fruit drop in sweet cherries. In some varieties it is hard to find any fruit at all. Many growers will not be harvesting the little crop that remains. A good amount of bird damage is being found in the remaining fruit, mostly from cedar waxwings and robins. Leaf spot control programs need to be maintained at least for the time being.

For growers with a crop of sweet cherries to harvest, you need to be concerned with spotted wing Drosophila (SWD) control. SWD trap catch started in all traps across the region mid-last week. Their numbers are low at this time but they are starting and can ramp up quickly. With the start of harvest for some blocks of sweet cherries, protection programs will need to start soon to control it.

Tart cherries have taken on a good sell in the last week and are starting to color. They are mostly 16 to 18 millimeters in diameter. As is the case in sweet cherries, I have seen a good amount fruit drop in tarts over the last five weeks. Most blocks only have 5 to 10% of a crop remaining. Many growers don’t have enough of a tart crop to even pick. Leaf spot control programs need to be maintained at least for the time being.

For growers with a crop of tart cherries to harvest, you need to be concerned with SWD control. SWD trap catch started in all traps across the region mid-last week. Their numbers are low at this time but they are starting and can ramp up quickly. With the start of harvest for some blocks of tart cherries, protection programs will need to start soon to control it.

Plums are 19 to 21 millimeters in diameter for European varieties, with Japanese varieties being 28 millimeters in diameter. As is the case for both sweet and tart cherries, most plum blocks have a poor crop due to freeze/frost damage.

Small fruits

Strawberry harvest continues across the region. Demand for both ready picked and pick your own strawberries continues to be very strong this season. Most growers have needed to close off picking in order to irrigate due to dry soils. Evaporative cooling of berries in the afternoon has been needed several times over the past week. Leaves on newly planted strawberries continue to emerge from the crown, with the flower trusses and runners continuing to emerge from the crown. Deflowering is taking place.

Most soils continue to be dry to very dry. Keep a close eye on soil moisture levels, as developing strawberries need a good amount of moisture, about 1.5 to 2.0 inches of either rainfall or irrigation a week. I am concerned that with low soil moisture supplies that were common when strawberries were in bloom that the second and subsequent pickings may have many small berries. Again, due to dry soils.

Sap beetles were found feeding for the first time late last week. Slugs or their feeding injury was found again last week at a few more farms. SWD trap catch started in all traps across the region mid-last week. Their numbers are low at this time but they are starting and can ramp up quickly. With the late strawberry season that we have this season, this pest could be a problem in end of the season strawberries. Stay tuned for details in next week’s report.

Gray mold was seen last week for the first time this season at just a few farms.

As I reported last week, I have seen or heard of a number of strawberry fields that appear to have had feeding injury for thrips earlier this season. The feeding was most likely from western flower thrips. However, I have not been able to find any adult thrips to aid in the identification of this pest. This is a difficult insect pest to scout for, as they do their feeding damage when flowers are opening and early in the flowering process, then they move on to feed on other plants. Western flower thrips do not overwinter in colder climates like Michigan. They come to Michigan with storm fronts from the south. The damage appears as seedy small berries that are bronze. Please be on the lookout for this feeding damage. Many times, the feeding damage will just be seen in a single variety that was at the right stage for thrips to do their damage.

Raspberry harvest is just beginning for early maturing summer red raspberries. Later maturing varieties are sizing well where soil moisture has been adequate. Where soil moisture has not been adequate, berry size is small. Growth has continued to be good on fall bearing raspberries, the tallest canes are 24 inches in length. Some light amount of raspberry cane borer damage is at just a few farms. Raspberry sawfly larva feeding damage is starting to be seen.

SWD trap catch started in all traps across the region mid-last week. Their numbers are low at this time but they are starting and can ramp up quickly. With the start of harvest for summer red raspberries, protection programs will need to start soon to control it.

Blueberries are beginning to swell; berry size is mostly between 8 to 12 millimeters in diameter. Early maturing varieties are coloring well.

Grape growth has moving quickly again week, with Concords at full bloom, other earlier flowering varieties are at BB sized fruit. Vinifera varieties are approaching bloom. Many new canes are 36 to 44 inches in length.

Saskatoon fruit have sized nicely and are coloring well in the past week. Most fruit are between 8 to 12 millimeters. Harvest of a few of the earliest maturing varieties will begin in the next few days. However, harvest will begin in seven to nine days on most varieties. New shoots continue to grow quickly, with most being 20 to 24 inches in length. Heavy bird feeding continues in saskatoons, mostly from cedar waxwings and robins.

Haskap fruit are mostly 8 millimeters in diameter. They are approaching harvest. Most of the fruit has been consumed by bird feeding over the last few weeks, mostly from cedar waxwings and robins. I have also seen some bushes collapse and turn brown over the last few weeks. It appears there was some freeze damage that occurred last November from the sudden cold snap, which occurred before plants were hardened off well.