Southwest Michigan fruit update — April 10, 2018

A chilly March has held plant development back. Plants are ready to grow when warm temperatures return later in April.

Winter temperatures and chill unit accumulation at the Southwest Michigan Research and Extension Center near Benton Harbor, Michigan. Note the coldest temperatures were just before New Year’s Day.
Winter temperatures and chill unit accumulation at the Southwest Michigan Research and Extension Center near Benton Harbor, Michigan. Note the coldest temperatures were just before New Year’s Day.

Winter

The winter of 2017-2018, was cold compared to 2016 and 2017. The cold temperatures were not as cold as the Polar Vortex years of 2014 and 2015 with lows near and below -20 degrees Fahrenheit. Temperatures during the 2018 winter dropped below zero at the end of December, with some areas reporting lows near -15 F. Growers report this winter cold did cause some damage, but this damage seems minor and localized.

Chilling requirements were completed for many plants during warm periods in January and February. Warm weather in late February caused plants to color up and bud swell was noticed in many plants. Little movement occurred in March because March was very chilly and temperatures rarely exceeded the 42 F temperature, above which many fruit grow. Currently, southwest Michigan is ahead of areas just a few miles to the north where no bud movement occurred.

Below are the growing degree-days (GDD) for the Southwest Michigan Research and Extension Center near Benton Harbor, Michigan, for the last 18 years. Table 1 is from Jan. 1 to April 8 and Table 2 is from March 1 to April 8.

Table 1. GDDs from Jan. 1 to April 8 at the Southwest Michigan Research and Extension Center for the last 18 years.

Year

Base 42 F

Base 45 F

Base 50 F

Ave

174

126

70

2018

81

50

18

2017

301

218

120

2016

201

143

76

2015

115

79

40

2014

49

29

12

2013

84

55

24

2012

460

370

249

2011

86

54

26

2010

240

182

110

2009

160

110

52

2008

111

75

37

2007

239

181

109

2006

135

92

43

2005

164

126

79

2004

166

116

61

2003

171

127

71

2002

97

57

20

2001

136

99

56

2000

306

223

123

March weather

Temperatures for most of March have been cool with lows at or below freezing and only a few warm days. There has been little bud movement since early March. The table below shows how cool March was in 2018. Normally, we would pick up 100 GDDs base 42 and 60 GDDs base 50 in March. In 2018, we only received about 20 GDDs base 42 and only 1 GDD base 50. This was the coldest March in the 18 years for which we have digital records at the Southwest Michigan Research and Extension Center.

Table 2. GDDs from March 1 to April 8 at the Southwest Michigan Research and Extension Center for the last 18 years.

Year

Base 42 F

Base 45 F

Base 50 F

Average

143

105

61

2018

18

8

1

2017

163

118

65

2016

176

128

71

2015

115

79

40

2014

47

28

12

2013

53

36

17

2012

437

358

245

2011

71

45

23

2010

238

181

110

2009

131

91

45

2008

74

49

23

2007

227

176

109

2006

110

79

42

2005

148

115

74

2004

144

102

55

2003

168

126

71

2002

53

33

14

2001

124

92

54

2000

216

158

88

Table 3. Southwest Michigan GDD Summary from Jan. 1 – April 9 2018.

Station

GDD 42 F

GDD 45 F

GDD 50 F

Benton Harbor (SWMRC)

81

50

18

Lawton (Lawton)

81

50

17

Fennville (TNRC)

67

42

15

Average for the SW region

83

51

18

Accumulation in March

20

9

1

The forecast for the upcoming week is for a brief warmup on Thursday and Friday, April 12 and 13, with highs climbing to around 70, followed by a return to cool wet weather.

Tree fruit

Temperatures below zero around New Year’s caused damage to some peach and sweet cherry fruit buds in some areas of southwest Michigan. Growers are generally encouraged by the slow start to the season. A slow start delaying bud growth reduces the risk of a damaging freeze in early spring. At this time, most fruit crops are still in the swollen bud or bud burst stage and it would require cold temperatures below 20 F to cause significant damage to tree fruit flower buds (see “Freeze damage depends on tree fruit stage of development”).

Tree fruit crop potentials are generally good. Cool and dry conditions for the last month have held back tree fruit development and allowed growers to make good progress in spring chores, including pruning. Recent rain and snow events have made any fieldwork and spraying difficult. Growers should check blocks for evidence of San Jose scale on branches to determine the need for oil sprays.

Apricots are in bud swell to early red calyx.

Peach and nectarine terminal fruit buds are showing first sign of swelling. Long episodes of wetting and temperatures above 50 F favor bacterial spot. Dormant sprays of copper or fungicides will reduce peach leaf curl. Low level of copper also suppresses bacterial populations.

In cherries, sweet cherry bud swelling is evident. Montmorency tart cherry fruit buds are still relatively tight. We are still in the window when copper sprays can be applied to sweet cherries. Copper applications may reduce bacterial canker in cherries

In plums, Japanese plum varieties are at swollen bud to early bud burst. European plums are relatively dormant. Thorough pruning of black knot and disposal of the knots by burning is an important step in managing this disease.

Japanese plum

Japanese plums are at swollen bud. Photo by Bill Shane, MSU Extension.

Apples generally show little or no bud swell. 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 fruit buds are at very early bud swell.

Small fruit

Grapes have not yet begun growth. There is some concern over winter lows, but most growers who have checked their buds report they still have numerous primary buds and the potential for a good crop.

Blueberry flower buds are only slightly swollen. Leaf buds do not appear swollen but warmer weather will bring on growth, making them susceptible to mummy berry infections. Many growers have already applied copper, Sulforix or lime sulfur products to suppress early season diseases.

Strawberries have greened up but new leaves are not emerging from the crown. Over-wintering 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. 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 Monday fruit IPM meetings have started. The next meeting is 5 p.m. on April 16 at Fruit Acres Farms, 3452 Friday Rd, Coloma, MI. Two Michigan RUP applicator recertification credits are available at these meetings.

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