Southwest Michigan fruit update – March 30, 2021

Mark Longstroth, William Shane<shane@msu.edu> and Michael Reinke<reinkem3@msu.edu>, Michigan State University Extension - March 30, 2021

March has been warm. Early fruit crops are showing movement.

Swollen apricot buds. — Apricot buds are swollen. With the warm forecast, expect rapid development of many tree fruits. Photo by Bill Shane, MSU Extension.

Winter

The winter of 2020-2021 was mild. Temperatures seldom dropped below 10 degrees Fahrenheit 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. A single deep freeze event occurred over the morning of Feb. 17 where temperatures in the region got down to zero to minus 10 F. No significant damage was reported. Early winter precipitation was above average. Since the first of the year, however, precipitation is half of normal. We are in a deficit and soils are dry.

Early ornamental plants started coloring up in early March. Some fruit crop buds started swelling in mid-March.

Below are the growing degree days for the Southwest Michigan Research and Extension Center (SWMREC) near Benton Harbor, Michigan, for the last 20 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 growing degree day (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 we are a little ahead of average.

Growing degree days from Jan. 1 to March 1 at SWMREC for the last 20 years.
Year	Base 42 F	Base 45 F	Base 50 F
Ave	25	15	6
2021	3	1	0

Growing degree days from March 1 to March 29 at SWMREC for the last 20 years.
Year	Base 42 F	Base 45 F	Base 50 F
Ave	82	60	58
2021	139	103	58
2020	76	49	20
2019	40	25	10
2018	16	7	1
2017	95	66	33
2016	142	103	56
2015	37	24	12
2014	11	5	0
2013	11	6	2
2012	370	312	223
2011	35	22	11
2010	86	55	21
2009	109	79	41
2008	17	8	2
2007	169	132	84
2006	52	37	18
2005	26	17	8
2004	112	82	46
2003	122	91	50
2002	38	25	12
2001	16	6	1

March weather

Temperatures for most of March have been warm with highs generally above average and occasionally in the mid- to upper 60s. Overnight temperatures have been in the 20s and 30s. Warm enough to prevent any damage. The table below shows how warm March was. Normally we would pick up 100 GDD base 42 and 60 base 50 in March.

Southwest Michigan GDD summary from March 1-29, 2020
Station	GDD 42 F	GDD 45 F	GDD 50 F
Benton Harbor (SWMRC)	139	103	58
Lawton (Lawton)	141	105	57
Fennville (TNRC)	112	81	44
Average for the SW region	137	102	57

The forecast for the upcoming week is for some cold mornings on Thursday and Friday with lows in the low to mid-20s then a return to warm conditions with highs in the 60s or 70s and lows above freezing for at least the next week. warming days with highs climbing into the 50s. The medium range forecast for the rest of April is for warmer than average weather, but lower than average chances of rain. The warmer than average chances continue through the rest of spring, but a return to average chances of precipitation once we get into May and June.

Tree fruit

The past winter was relatively mild, with the only somewhat significant dip on Feb. 17 down to -4 to -10 F. This episode may have affected some peach fruit buds in a few sites. In general, the tree fruit crop prospects are still really good. The string of warm days and nights from March 20-25 accelerated fruit tree development, but not excessively.

Dry conditions for the last month allowed growers to make good progress pruning. Check blocks for evidence of San Jose scale on branches to determine the need for oil sprays.

Apricot buds are visibly swollen but not showing any blossom tissue yet.

Peach and nectarine fruit buds have swollen significantly over the weekend, with green tissue starting to show on terminal buds. The rains of last week were likely sufficient for peach leaf curl infections. Infections require 10+ hours of wetting with temperatures in the range of 46 to 55 F. Even if the spray for this disease has not been applied, application now can help suppress additional infections when these weather conditions occur even past bud swell. Low levels of copper also suppress bacterial spot populations.

In cherries, there is visible bud swell. We are still in the window when copper sprays can be safely applied to sweet cherries. Copper applications may reduce bacterial canker in cherries.

In plums, Japanese plum fruit buds are visibly swollen with European plum lagging behind. 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.

Apple began showing green tissue last week on early varieties such as Zestar, Idared, Red Delicious and McIntosh. Local monitoring sites showed significant apple scab ascospore catches during the March 23-24 wetting period and the weather conditions may have be sufficient for a few sites for an infection period, especially in the Lawrence and Lawton areas. Scab sprays will be needed to protect against future rains. Copper sprays can provide early scab control and fire blight suppression. Protectants are preferred over systemic fungicides at this time of year for scab control.

Pear buds are visibly swollen.

Small fruit

Grapes show no movement.

Blueberry flower buds appear swollen; leaf buds do not show growth yet. 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 starting to emerge from the crown. Overwintering mulches should be removed and raked between the rows. Some growers are putting out floating row covers. Growers are looking at early season herbicides to control overwintering weeds.

Brambles show some movement with swollen buds. 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

Our regular southwest Michigan Monday Fruit IPM Updates are available online. Our first meeting is Monday, April 5, at 5:30 p.m. You need to register to receive the Zoom link and password for these meetings. The webinars are free and one pesticide applicator credit is available for each meeting. We had over 70 growers attending our Monday meetings last year.

The Statewide Spring Tree Fruit Webinar series will be the first two weeks of April. One topic will be discussed over the lunch hour each day. You need to register to receive the Zoom link and password for these presentations. The webinars are free and one pesticide applicator credit is available for each meeting.