Southwest Michigan fruit regional report – April 14, 2013

Cool, wet weather is holding back plant growth this spring.


Cool rainy weather is holding plant development back. There is very little difference in Growing Degree Days (GDD) across the southern region. The northern sites have accumulated fewer GDDs. This difference is even more pronounced to the north where Ottawa and Kent counties did not receive the warm days last week. We are lagging well behind our normal development. Comparing the GDD accumulations since 2000 at Southwest Michigan Research and Extension Center shows that we have only about a third of the heat units we normally do. We are probably 10 to 14 days behind normal. High temperatures were generally in the upper 40s last week with little growth. Several warm days and nights did get growth moving. Low temperatures stayed above freezing at night. This week will be warmer with highs in the 50s and 60s. Lows generally will be above freezing with mild freezes over the weekend.

Southwest Michigan Regional GDD Summary
from March 1 to April 14, 2013









Bainbridge / Watervliet




Benton Harbor (SWMREC)




Berrien Springs












Grand Junction












Lawrence / Teapot Dome








South Haven




Average for the region




Several large rain events will move though the area. Continuing showers and warmer weather will allow plant growth to continue slowly. Green tissue is emerging or about to emerge, so this week and next will be the initial infections for many fruit diseases. Many areas received 2 to 3 inches of rain last week. Many soils are at field capacity and areas with poor drainage are saturated with standing water in the fields. There is still time to apply dormant treatments to protect crops. Check your local weather station and conditions at Enviro-weather.

Tree Fruit

Tree fruit growth has progressed markedly over the last week. Buds are swollen and beginning to open on the early blooming varieties. First bloom is at least 1 to 2 weeks away for stone fruit. At this stage of development it would require cold temperatures below 20 degrees F to cause serious damage to the most advanced tree fruit buds. See the Michigan State University Extension article on Freeze damage depends on tree fruit stage of development. Early season oil and insecticide sprays for San Jose scale, mites, and aphids are a good option if weather permits. Oil sprays should not be applied if there is a danger of a freeze in the following two days.

Apricot buds are at red calyx.

Peach fruit buds are at green to red calyx. Leaf buds have leaves emerging, exposing green tissue. The cool wet weather is favorable for peach leaf curl infections. For peaches and nectarines, which have not been treated for peach leaf curl, a Bravo spray as soon as weather permits will help suppress further infections. Copper applications for bacterial spot will help to suppress bacterial populations that will damage leaves and fruit after bloom. See Management of bacterial spot on peaches and nectarines for more details.

In cherries, sweet cherry buds are in the side green to green tip stages. If you still need to apply copper to reduce bacterial canker, when it warms up and buds break that is the end of the early season copper spray window. Tart cherry buds are at green tip in Berrien and Van Buren Counties. Montmorency cherries are much more tolerant of copper so growers still have time to apply this material.

Green tip in Montmorency tart cherries is common throughout the region.
Green tip in Montmorency tart cherries is common throughout
the region. Photo credit: Mark Longstroth, MSUE

In plums, both Japanese and European fruit buds are at late bud swell, called white side in plums. Low rate copper sprays now will help suppress bacterial spot symptoms after bloom. Soon growers will need to start their black knot control programs. Black knot infects actively growing green shoot tissue. The trees are susceptible from first green buds until active shoot growth slows down in early to mid-summer. Black knot infections are favored by temperatures from 55 to 77 degrees F accompanied by rain.

These Japanese plums are at late white side and are ready to burst open.
These Japanese plums are at late white side and are ready to burst
open. Photo credit: Mark Longstroth, MSUE

These European plum buds are just beginning to swell and are showing early white side.
These European plum buds are just beginning to swell
and are showing early white side. Photo credit: Mark Longstroth, MSUE

The most important fungicide treatment time is from first color on flower buds to about three weeks after bloom when the combination of favorable temperatures, spore availability, and plum susceptibility coincide. Fungicide sprays help prevent new infections but will not stop infections that are already present on the tree. Fungicides with protective activity against black knot include Indar (good), Pristine (good), Bravo [chlorothalonil] (good to excellent), Topsin M 70 WP 1.5 lb. or Topsin M 70 WP 1 lb. + Captan 50 WP 2 lb. (good to excellent), Captan 50 WP 6 lb. (fair). Fungicides with little or no activity include Rovral, Vangard and Orbit. Sulfur fungicides at high rates have some activity. Ziram is not labeled on plums.

Apples range from early green tip to quarter-inch green in Berrien County. Most apples are still at silver tip in the rest of the region and green tip is expected on the next warm day. Green tip signals the start of apple scab spore release and the need to apply fungicides. Older protectant fungicides such as mancozeb, captan, and ziram are generally more economical ($30 or less per acre) than newer systemic fungicides that can range $30 to $55 per acre). The best savings is for early sprays with protectant fungicides before pink when powdery mildew sprays are not yet needed. A copper spray for the first scab spray at green tip can also suppress fire blight. Copper applications should not be used for fresh market apples once the flowers buds are exposed (e.g., tight cluster) to avoid phytotoxicity and russetting of the fruit finish.

Pear buds have swollen markedly over the past week. Pear scab control is needed as susceptible green tissue emerges.

Small fruit

Grapes appear mostly dormant but scales have cracked on a few buds. This indicates that grapes are ready to go when we get warmer temperatures above 50F. There is still time to make a dormant application of lime sulfur, sulfur or copper to reduce inoculum of phomopsis, anthracnose, black rot powdery and downy mildew. See the article There is still time for dormant sprays in grapes. This may be of benefit to growers whose vineyards developed problems with these diseases last year under minimal fungicide application regimes. Check page 179 in MSU Extension bulletin E-154 to determine whether or not the grape varieties you are spraying are sensitive to copper or sulfur. As buds develop, climbing cutworms and grape flea beetles will be the insect pests to watch out for.

Blueberry flower buds on are beginning to swell and flower buds are bursting in southern Berrien County and green tissue is out over most of Berrien County. Many fields are showing a lot of dead and weak wood as a result of last year’s drought. Leaf tissue is just starting to appear in early varieties in Van Buren County. As leaf tissue appears mummy berry infections are possible. The rainy weather forecast looks ideal for mummy berry. Growers should be scouting for mummy berry apothecia (also called mushrooms or trumpets). See Scouting and management of mummy berry in blueberries.

Mummies have been found in wet sites. Most apothecia are about 1 mm; but some are approaching 2 mm, when spore release begins. Spores are generally released under dry conditions, not during rains but free water is required for the spores to germinate and begin infection. See the article, Understanding mummy berry shoot strikes for more information on the infection conditions necessary for mummy berry shoot strike, including temperature and wetness requirements. Freezes increase the susceptibility of tissues to infection, so protectant materials should be applied before freezes while systemic materials should be applied quickly after a freeze. See E-154 the Michigan Fruit Management Guide for more information on fungicide sprays for mummy berry control.

Strawberries are greening up and new leaves are emerging. The flower trusses are not visible in the ground. Overwintering mulches should be removed and raked between the rows. Strawberries in the high tunnels are putting out new leaves and flower trusses and have a few open flowers.

Bramble buds are moving but little green tissue is visible. New primocanes are beginning to emerge from the ground. Dormant pruning cutting back last year’s primocanes should be completed soon. Fall bearing raspberries should be cut or mowed to the ground. Lime sulfur treatments for anthracnose should be applied. Raspberries growing in the high tunnels and in bags of soilless mix are considerably more advanced than raspberries growing in the field. Some of the high tunnel raspberries have new growth of 2-5 inches.


Our next weekly Monday fruit IPM meetings is on April 22, 2013, at Fruit Acres Farms at 5:00 p.m. These weekly meetings are good for one RUP credit and will continue through the end of June.

There is still time to register for the first in-season grape meeting, on April 24, 6:00 p.m. to 8:00 p.m. at the Berrien County Extension Office, 1737 Hillandale Rd., Benton Harbor, Mich. Annemiek Schilder will cover updates on fungicides and a new grape virus factsheet that will be available this year. We will also discuss soil testing and nutrient applications. Registration is $15 and includes a light supper for those who preregister and prepay by April 22. Two RUP credits are available.

The Paw Paw Code-A-Phone, (269) 657-8217 is now active. This 3-minute recorded message reports on current pest and disease issues in fruit.

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