MSU Extension

Weather

Last week was hot and dry. A strong line of storms crossed the region Sunday night, Aug. 2, dropping much needed rain. This was the first significant rain in the region since July 18. Last week’s high temperatures were in the upper 80s and lows around 60. About an inch of rain dropped Sunday night with rainfall totals ranging from 0.5 to 1.75 inches. Some growers reported over 2 inches. Top soils were becoming very dry and crops had begun to wilt in the field. Growers with irrigation were irrigating sandy soils. Evapotranspiration last week was about 1.5 inches, with 0.2 to 0.25 inches of water a day. Evapotranspiration this coming week will be less, about 0.2 to 0.15 inches of water a day. We expect soils will dry out again quickly.

Weather for the upcoming week will be cooler. Highs will be around 80 and lows around 60. There is little chance of rain until late in the weekend. Last week, our daily GDD accumulation was about 33 GDD base 42, 30 GDD base 45 and 25 GDD base 50 per day. This was the warmest week we had so far, but we expect less heat accumulations this coming week, about 25 GDD base 42, 25 GDD base 45 and 20 GDD base 50 per day. We are a little behind normal in heat accumulation.

We are close to average in rainfall with an average of 16 inches for the region. The wettest year in the last five years was 2011 with about 20 inches, and the driest year was 2012 with about 10 inches. We are above the five-year average of about 15 inches. See the last five years at the Southwest Michigan Research and Education Canter (SWMREC).

Tree fruit

Now is the time to pull leave samples in tree fruit for tissue sampling. Soil moisture is low in top soil, but reserves are still available in the subsoil. Foliar diseases are common in some orchards. Oriental fruit moth is still flying. Obliquebanded leafroller adult trap catch is declining, but larvae of the second generation can be found webbing leaves and chewing holes in foliage. The Trevor Nichols Research Center (TNRC) trap catches of San Jose scale male adults continue to be high for the second week. San Jose crawlers are expected approximately 500 growing degree days (GDD) base 51 from the July 20 biofix, estimated to be approximately Aug. 13. Sprays for crawlers are timed approximately 150 GDD51 later, or approximately Aug. 20. Deer feeding is continuing in young plantings with new growth as the fawns become old enough to browse on their own. Crows are a major problem in peaches and apples with red-colored fruit.

Apricot harvest is over.

Peaches are growing rapidly. Red Haven, Starfire, PF9A-007 and Redstar harvests are underway in central Berrien County. Sunny days and cool nights are helping peaches develop excellent sweetness. Estimated peach harvest dates are available on MSU Enviro-weather. We are interested in grower feedback on the accuracy of this model from growers who use it to predict harvest in their orchards. Modest summer pruning one to two weeks before harvest will help poorly coloring varieties to improve their blush.

Brown rot continues to be a problem on ripening fruit with rain and warm weather, especially damaged by insects or with split pits. Growers should rotate fungicide types to avoid fungicide resistance problems. Recent dry weather has slowed new bacterial spot infections, with infected leaves yellowing and dropping. Peach scab is showing up in stem bowls and elsewhere on fruit where fungicide coverage has been scanty.

Oriental fruit moth trap catches continue to be high in some orchards. Other direct fruit pests include tarnished plant bug and the common stink bug, which cause pinhole punctures on fruit. Spotted wing Drosophila (SWD) is a potential problem in peaches picked on the mature side of ripe trees. Infested harvested fruit may be stored at 35 degrees Fahrenheit or lower for at least 96 hours to kill developing eggs, larvae, pupae and adults. Peachtree borer moths are still flying in area orchards and have the potential for egglaying in limb and trunk wounds.

Sweet cherry growers need to maintain protectant fungicide coverage to reduce cherry leaf spot. Modest pruning can be done after harvest on trees that have filled their space.

Tart cherry growers need to maintain protectant fungicide coverage to reduce cherry leaf spot. Some orchards have already been defoliated. Most growers applied chlorothalonil after harvest to protect their remaining leaves. Growers using copper should avoid copper building up on leaves and discontinue copper use when there is little or no rain between sprays. Trunk sprays after harvest can be used to suppress trunk borer problems. Like in sweet cherries, modest pruning can be done post-harvest on mature trees that have filled their space. Unharvested cherries on the trees have been infested by cherry fruit flies and spotted winged Drosophila (SWD) vinegar flies. It probably does not pay to apply a revenge spray to kill these pests unless you have ripening fruit in the area and need keep pest pressure down.

Japanese plum harvest of Shiro, Early Magic, Ozark Premier and Vanette is or will shortly be underway. Apple maggot, oriental fruit moth, codling moth and obliquebanded leafroller can infest fruit if it is not protected. Spotted winged Drosophila is also a potential problem for plums picked on ripe trees. Bacterial spot and brown rot are the primary disease problems for plum fruit. Pitting and gumming of fruit is generally due to bacterial spot, which is a particular problem on Castleton, Stanley and Vision European plum varieties.

Apple estimated harvest dates are available from MSU Enviro-weather for weather stations across Michigan. Some of these dates include Sept. 8 for McIntosh and Sept. 30 for Red Delicious for central Berrien County. View a more detailed list of apple variety harvest dates for west central and southwest Michigan. Apple maggot adults continue to be caught at the TNRC. Apple maggot adults emerge after rain, so expect their numbers to increase this week. Trapping with yellow sticky boards is a good method to determine if this pest is present.

Fire blight spread is slowing as orchards cease active terminal growth. The fungal disease bitter rot can be found on fruit. Growers need to include fungicides in some of their cover sprays to control sooty blotch and flyspeck. Growers should reapply fungicides for these two diseases whenever the hours of leaf wetness exceed 250 since the last fungicide application. Growers with a light crop or with bitter pit-susceptible varieties should include calcium in their cover sprays to reduce bitter pit. We are still catching codling moth of the second generation flight. Oriental fruit moth trap catches are high in some orchards. Growers should be scouting for obliquebanded leafroller larvae. Green aphids are increasing on active shoot growth.

Pear crop potential is good. Clapp Favorite harvest is about two weeks away.

Small fruit

Japanese beetles are easy to find. You can expect Japanese beetles to increase after Sunday’s rain. We are catching more SWD in southwest Michigan. Almost all traps are catching flies and trap numbers are doubling each week. SWD is a pest of ripening fruit and numbers increase as wild berries ripen.

Grapes are at cluster tightening. We are seeing veraison in early coloring grapes. The third generation of grape berry moth is predicted to begin egglaying around Aug. 8 in Berrien County and Aug. 9 or 10 in Van Buren County. See “Grape berry moth pressure lower in 2015 – control window approaching for southern Michigan” by Michigan State University Extension for more information.

Juice and wine grape berries are resistant to new fungal disease infections. We are getting dew almost every morning, so this is the time when downy mildew can really move quickly in a vineyard. Growers need to protect the leaves of susceptible varieties. Wine grape growers should apply a botrytis fungicide at veraison to reduce late-season fruit rots. Black rot fruit infections that occurred earlier in the season when juice grapes were susceptible to the disease are showing symptoms now.

Scout for potato leafhoppers in wine grapes, which are in the area. Grape leafhoppers are scarce in juice grapes. Japanese beetles are feeding on leaves in some vineyards, and have been seen in greater numbers over the last few weeks. Usually only severe outbreaks of these insects require treatment.

Blueberry machine harvest is well underway and blueberry harvesters are a common sight. Many growers were out reapplying protectant materials for SWD after Sunday’s rain. SWD numbers are increasing in fencerows as wild fruits ripen. Blueberry harvest is moving quickly. ‘Bluecrop’ harvest is winding down. ‘Jersey’ harvest is picking up and ‘Elliott’ harvest will start soon. Now is the time to pull leave samples in blueberries for tissue sampling.

Many blueberries are harvested using machines rather than hand-picked. Hand-harvest labor is scarce and expensive.

Scouts are catching blueberry maggot flies and SWD. In non-irrigated fields, blueberry maggot numbers are decreasing without any rain, but SWD numbers are doubling every week in most locations. Ripening fruit needs to be protected from these pests. Frequent picking reduces the amount of time the fruit is availble to these pests. Growers should be testing fruit for larvae, many soft fruit are infested. Growers should apply fungicides to protect fruit from anthracnose and alternaria fruit rots and new shoots from stem blights such as phomopsis.

Soil conditions have been dry and irrigation systems should be running. The potential evapotranspiration this week is less than a fifth of an inch per day or about 0.75 inches for the week. This is all the rain many growers received in Sunday’s rain, so irrigation will be needed later this week. The rooting zone of blueberries is about 18 to 24 inches, and our sandy soils hold about 1.5 to 2 inches per foot. Under these hot, dry conditions mature blueberry bushes use about 3 to 4 gallons of water a day. Growers need to maintain soil moisture above 50 percent available water in the root zone. See “Irrigating Michigan blueberries” for more information.

Strawberry fields are putting out new leaves after renovation. Growth is good in irrigated fields, but poor in unirrigated fields. Be sure to protect newly emerging leaves against potato leafhoppers and strawberry foliar diseases.

Raspberry harvest has ended in summer red raspberries. SWD and Japanese beetles are out and can be a problem in raspberries. Primocanes bloom continues on fall bearing red raspberries. Primocane bearing blackberries are also blooming. Protect pollinating bees and avoid spraying insecticides during bloom. This is a problem for growers trying to double crop everbearing red raspberries with fruit on floricanes and bloom on primocanes.

Growers with ripening fruit need to time their SWD controls with harvest and pay close attention to the pre-harvest intervals (PHI) on the pesticide label. Raspberries are also very attractive to SWD and growers should pay close attention to protecting against this pest. Blackberry leafminers were found in blackberries. This pest has two generations per year and we are seeing the first generation in leaves now and they are large, indicating they will fall to the ground and pupate soon. This pest prefers certain varieties, so treatment is only necessary on this affected varieties.

Blackberry leafminers chew out the mesophyll of the leaf, leaving the top and bottom layers intact. These leafminers are related to raspberry sawflies. The second generation will emerge later in August.

See also

• Controlling cherry leaf spot in orchards with existing symptoms
• Peach harvest dates available on MSU Enviroweather
• Sooty blotch and flyspeck disease of apple and pear
• Bitterpit control in apples
• Predicted 2015 apple harvest dates
• Managing Japanese beetles in fruit crops
• Don’t let bunch rots ruin your grapes
• SWD website for more information
• Where else does spotted wing Drosophila like to feed?
• Irrigating Michigan blueberries
• Assistance in raspberry virus diagnosis offered
• Protect strawberries from foliar diseases after renovation