Southwest Michigan fruit update – March 25, 2020

Mark Longstroth, William Shane<shane@msu.edu> and Michael Reinke<reinkem3@msu.edu>, Michigan State University Extension - March 25, 2020

With warmer weather in March, the snow has melted and plant growth is starting.

Peach leaf curl infects the peach buds as they start to swell. Preventative sprays are applied before early bud swell. Photo by Mark Longstroth, MSU Extension.

Winter

The winter of 2019-2020 started with a hard freeze to about 10 degrees Fahrenheit in mid-November. The winter was mild. Temperatures seldom dropped below 10 F and most plants had completed their chilling requirements by early January for peaches and grapes. Other fruit crops with a higher chilling requirement such as apples, blueberries, cherries, pears and plums reached this point by late January. Little bud movement occurred in February and March with temperatures rarely exceeding 42 F, the temperature above which many fruits will grow. After mid-March, warmer temperatures melted the snow and plant wood tissues began to color up. Currently, southwest Michigan is ahead of areas just a few miles to the north where no bud movement has occurred.

Below are the growing degree days (GDD) for the Southwest Michigan Research and Extension Center (SWMREC) near Benton Harbor, Michigan, for the last 18 years. There are two tables, one from Jan. 1 to March 1 (January and February) and the other from March 1 to March 31. The GDD totals for January and February also indicate we had little warm weather in the winter. Compare the 2020 numbers to the average for the last 20 years and you can see that we are a little behind average.

GDD from Jan. 1 to March 1 at the SWMREC for the last 20 years.
Year	Base 42 F	Base 45 F	Base 50 F
Average	30	20	8
2020	20	10	1

GDD from March 1 to March 31 at the SWMREC for the last 18 years.
Year	Base 42 F	Base 45 F	Base 50 F
Average	59	43	25
2020	43	29	12
2019	20	13	6
2018	5	2	0
2017	47	32	15
2016	119	87	47
2015	37	24	12
2014	9	3	0
2013	9	6	2
2012	325	280	207
2011	35	22	11
2010	75	49	19
2009	87	65	36
2008	14	8	2
2007	70	52	30
2006	47	35	18
2005	10	6	1
2004	31	18	7
2003	73	53	28
2002	38	25	12
2001	13	5	1
2000	125	96	59

March weather

Temperatures for most of March have been cool with lows at or below freezing. Noticeable bud development of woody ornamentals is only just beginning. The table below shows how cool March was. Normally, we would pick up 100 GDD base 42 and 60 GDD base 50 in March. We are about a week to 10 days behind normal. This could easily change depending on how quickly we warm up. To remind us that it is spring in Michigan, most of the region had about an inch of snow Sunday night (March 22).

Southwest Michigan GDD summary from March 1 – 31, 2020
Station	GDD 42 F	GDD 45 F	GDD 50 F
Benton Harbor (SWMRC)	43	29	12
Lawton (Lawton)	42	27	11
Fennville (TNRC)	38	25	10
Average for the SW region	42	28	12

The forecast for the upcoming week is for warming days with highs climbing into the 50s. Nighttime lows will be above freezing in the 30s. Rain is forecast for Friday, March 27. The weekend highs should climb to near 70. The following week should see a return to more normal weather.

Tree fruit

We do not expect to see any winter injury this year, although some trees have persisting problems from January 2019 low temperatures. Growers are generally encouraged by the slow start to the season. A slow start delays bud growth, which reduces the risk of a damaging spring freeze. Tree fruit buds should begin to swell soon. Tree fruit crop potential is good. Cold and dry conditions for the last month allowed growers to make good progress pruning. Soils have only just begun to dry out, making fieldwork and spraying difficult. Growers should check blocks for evidence of San Jose scale on branches to determine the need for oil sprays.

Apricots buds are not swollen.

Peach and nectarine buds should begin to swell soon. Dormant sprays of copper or other appropriate fungicides will reduce peach leaf curl. Low levels of copper also suppress bacterial spot populations.

There is no bud swell in cherries. We are still in the window when copper sprays can be safely applied to sweet cherries. Copper applications may reduce bacterial canker in cherries.

Japanese and European plums are relatively dormant. Prune out black knot and dispose of the knots by burning or removing from the orchard. Sanitation is an important step in managing this disease.

Apples show no bud swell. We expect to see silver tip early next week. The current cool temperatures will allow scab ascospores to mature so that more spores will be available in the early stages of apple development. Copper sprays will be going out soon for early scab control and fire blight suppression.

Pear buds show no movement.

Small fruit

Grapes show no movement.

Blueberry flower buds and leaf buds do not appear swollen. Fields are very wet. Growers still have time to apply copper, Sulforix or lime sulfur products to suppress early season diseases.

Strawberries have greened up, but new leaves are not yet 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.

Brambles show little movement. Dormant pruning should be completed soon. 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.

Upcoming meetings

Due to restrictions on travel and large meetings, our grower meetings will be moving online. We are planning and developing these meetings as quickly as we can. Please look for announcements of these meetings. These times and dates are tentative.

Preseason southwest Michigan fruit update: Thursday, April 2, 7-8:30 p.m.
Blueberry kickoff meeting: Friday, April 3, 1-4 p.m.
Grape kickoff meeting: Thursday, April 23, 1-4 p.m.
Southwest Michigan Monday fruit updates will be online starting April 13.
Spring tree fruit online meetings are planned for the noon hour starting April 13.

This article was published by Michigan State University Extension. For more information, visit https://extension.msu.edu. To have a digest of information delivered straight to your email inbox, visit https://extension.msu.edu/newsletters. To contact an expert in your area, visit https://extension.msu.edu/experts, or call 888-MSUE4MI (888-678-3464).