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Southwest Michigan Fruit Update – April 7, 2020

Southwest Michigan Fruit Update – April 7, 2020
By Mark Longstroth and William Shane
The weather for the first week of April was mild. There were a few mornings below freezing but generally temperatures were above freezing and highs in the 40s and 50s. Bud swell continues and many buds are opening. Soils are moist and soil temperatures are averaging 50 degrees Fahrenheit.
Rain for the week including Tuesday morning is about a third of an inch for the region. The next few days will have highs in the 60s and 70s with scattered showers. Cooler, drier conditions will return late in the week. A cold front will drop high temperatures into the 40s for the weekend. We expect next week to be cold and windy.
We picked up 18 growing degree days (GDD) base 42 and 8 GDD base 50 last week. The 20-year average for the Southwest Michigan Research and Extension Center is 123 GDD42 and 52 GDD50. We are about a week behind our long term average.

Southwest Michigan GDD summary from March 1 – April 5, 2020


GDD 42 F

GDD 45 F

GDD 50 F

Benton Harbor (SWMRC)




Lawton (Lawton)




Fennville (TNRC)




Average for the SW region




Average last week




Tree fruit
Growers are encouraged by the season’s slow start. Delayed plant growth reduces the risk of a damaging spring freeze. Fruit tree buds are swelling and bursting open. It would take cold temperatures down below 23 F to cause damage to the most advanced flower buds. Tree fruit crop potential is good. Cool and dry conditions allowed growers to make good progress pruning.
Check blocks for evidence of San Jose scale on branches to determine the need for oil sprays. The window for using oil on stone fruit closes as the buds open. Bud development has moved quickly in the last few warm days. As the buds develop, they become less tolerant of cold so that by bloom, temperatures below freezing will kill the flowers. Currently there is a wide range between the temperature that would cause a little damage and colder temperatures that would kill most of the flowers. For more information, see “Freeze damage depends on tree fruit stage of development.
We are a week or more from our normal bloom dates for tree fruit. Normally, tree fruit are blooming in sequence the last week of April for stone fruit and the first week in May for apples.
Apricots are at white bud. At this stage, the flower buds would be hurt by temperatures below 25 F. Apricots are the first stone fruit to bloom. The normal bloom date for apricots in southwest Michigan is around April 18. Bloom begins earlier in Berrien County.
Peach and nectarine buds are at green calyx and some pink is visible in early varieties at the Southwest Michigan Research and Extension Center. At this stage, the flower buds would be hurt by temperatures below 22 F. Low levels of copper before bloom suppress bacterial spot populations. The average bloom date for apricots is around April 27.
Cherry buds are swollen. Depending on the variety, cherry flower buds would be hurt by temperatures below 23 F. Normally, sweet cherry bloom begins around April 25. There is a lot of variation in bloom timing for early mid and late bloom. Sweet cherries and peaches are blooming at the same time. Montmorency tart cherry bloom in later the end of April.
In plums, Japanese plums are at tight cluster and would be hurt by temperatures below 24 F. Japanese plums bloom very early, beginning around April 21. European plum buds are only swollen and should be able to withstand 20 F. European plums bloom later, with first bloom around April 29. Finish pruning out black knot and dispose of the knots by burning or removing from the orchard. Sanitation is very important in managing this disease.
Apples buds are at green tip. Now is when growers need to apply a spray to control apple scab. Scab ascospores have been caught following recent rains in Berrien County. Spore numbers really jumped with Tuesday’s, April 7, rain. Copper sprays for early scab control and fire blight suppression should be applied soon. Apples normally bloom the first week in May in southwest Michigan
Pear buds are swollen. Pears bloom at the end of April.
Small fruit
Grapes show no movement. We normally begin to see movement in mid-April as temperatures are above 50 F. We see color in the buds at the end of April and leaves unfolding in early May. There is still time to apply dormant sprays for early season disease control.
Blueberry flower buds are swollen. Leaf buds are at green tip in the warmer areas of the district. Scout for mummy berry mushrooms (apothecia) and begin applying controls. Fields are very wet. Growers still have time to apply copper, Sulforix or lime sulfur products to suppress early season diseases. Blueberries normally bloom the second week in May.
Strawberries have greened up and new leaves are emerging from the crown. Overwintering mulches should be removed and raked between the rows. Growers are looking at early season herbicides to control overwintering weeds. If the flower trusses are below ground, there is little danger of freeze damage to flowers below ground.
Brambles are at green tip. Now is the time for lime sulfur sprays to suppress anthracnose. Dormant pruning should be completed. In summer bearing raspberries, last year’s primocanes should be headed (cut back) to the desired height and any remaining floricanes from last year should be removed. Fall bearing raspberries should be cut or mowed to the ground. Lime sulfur treatments for anthracnose can still be applied. If the leaves have begun to unfold, the rates need to be reduced to prevent injury
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