Southeast Michigan fruit update – May 2, 2023
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EmailGrowers in the region are preparing for apple bloom.
Welcome to the fourth in-season fruit article update for southeast Michigan for the 2023 season. Throughout the season these updates will include information about the weather in the past week and the upcoming week, a fruit-by-fruit guide to current conditions with appropriate pest and disease updates, and other relevant observations.
General observations
Due to the cold weather we have had in the last couple weeks, we haven’t seen much movement in our fruit crops’ bud development. Despite freezing temperatures last week, I haven’t seen much damage on my site visits nor have growers reported much to me. We continue to see blossoms in cherries, peaches and plums in some parts of the region. We expect another two days of rain and cool weather, but we are expected warmer and drier conditions later in the week.
The continued chance of rain means that disease risk will still be present. Based on the RimPro models at the Romeo station, we are expecting continued potential for apple scab infection through Thursday (May 4) and a potential spike in infection risk around May 10. The risk of economic loss due to scab is highest early in the season because it is a disease that will recur and intensify with successive generations.
Not much insect movement has happened in the last week because of the cool temperatures. I will be setting up traps for the southeast Michigan trap line in the next week. With apple bloom imminent this is a good chance to review this 2022 article on reducing pesticide risks to bees during fruit crop bloom.
I encourage our growers to attend the weekly southern Michigan grower meetings virtually on Monday evenings by registering online. It is a good opportunity to ask questions and receive RUP credits. See the latest weekly fruit meetings for Southern Michigan on MSU’s Kaltura Mediaspace (these may take a few days to upload after the Monday meetings).
Fruit-by-fruit conditions
Apples: We have not moved much in our growing degree day (GDD) accumulation, no blooms have been reported yet in southeast Michigan, but some cultivars are flowering in the southwest. Apples in Novi, MI, are at pink. Further north in Fenton and Romeo, MI, on Monday the apples were primarily pink with some varieties lagging behind in tight cluster. RimPro is currently reporting a lingering risk of a scab infection through the next day of continued rain and potentially again around May 10. Critical temperatures for apples at tight cluster are 27 degrees Fahrenheit for 10% kill and 21 F for 90% kill. At the full pink stage, they are 28 F for 10% kill and 25 F for 90% kill.
It is also time to prepare for whether and how you may want to treat your trees during bloom for crop load management, thinning and ensuring return bloom. This article from 2022, “Honeycrisp crop management for 2022,” outlines some steps you can take (this was written with high-density Honeycrisp in mind).
Blueberries: We have tight cluster to early pink bud in blueberry plantings in Fenton. This is the primary risk period for mummy berry and it is time to start paying attention to phomopsis. FRAC 3 fungicides are reported to be efficacious for both mummy berry and phomopsis. The critical temperatures for damage for blueberries are bud swell 10-15 F, tight cluster 20-23 F and early pink bud 23-25 F.
Brambles: We are seeing growth in both red and black raspberries in Washtenaw County and Romeo as well as in southwest Michigan, though the cool temperatures have slowed the growth. We are still prebloom so there is still time for delayed dormant sprays. See the Fruit Management Guide (E-154) for more information.
Cherries: We are seeing some petal fall in sweet cherries in Romeo as well as first blooms in tart cherries in Novi, Fenton and Romeo. Expansion of first bract leaves, which likely happened in the last week depending on your location, is the beginning of risk period for cherry leaf spot. The critical temperatures for sweet cherries at full bloom are 28 F for 10% kill and 25 F for 90% kill. The critical temperatures for tart cherries from open cluster to full bloom are 28°F for 10% kill and 24°F for 90% kill.
Grapes: We have seen first bud swell in Fenton and full bud swell in Marquette vines in Ray Township, though we have not seen the first leaves. The critical temperatures for grapes (hybrid and vinifera) at first are 13 F for 10% kill and 7 F for 50% kill. The critical temperatures grapes at full swell are 26 F for 10% kill and 21 F for 50% kill.
This slow grape bud development period is a good chance to monitor for cutworms and flea beetles. See “Bud swell is the time for monitoring vineyards for cutworms and flea beetles” for scouting guidance (note the Lorsban recommendation is out of date).
Strawberries: Vegetative growth continues in field strawberries in Romeo. In southwest Michigan, bloom is starting on protected plants. Flowers can be killed at 10 F temperatures while still in the ground and at 20 F temperatures once emerged. Early season fungicides should focus on controlling leaf spot.
Peaches and nectarines: Peaches in Fenton have started to bloom and blooming continues in Romeo. At full bloom, critical temperatures are 27 F for 10% kill and 24 F for 90% kill.
Pears: European pears observed at Novi are blooming. Asian pears observed in Macomb are blooming. Some pear psylla has been spotted in west central Michigan. At full bloom, the critical temperatures for pear are 28 F for 10% kill and 24 F for 90% kill.
Plums: uropean plums observed in Fenton are at petal fall. The critical periods for most fungal control is for petal fall to late June, but for brown rot specifically the critical times are during bloom and later on at fruit coloring. The critical temperatures for European plums in full bloom are 28 F for 10% kill and 23 F for 90% kill.
Insect conditions
Our main message from our IPM (integrated pest management) educators is to avoid applying insecticides during bloom! Many insecticides will also harm or kill bees and other pollinators that are necessary to ensure a good fruit crop. With apple bloom imminent this is a good chance to review this 2022 article on reducing pesticide risks to bees during fruit crop bloom.
In tree fruit, our insect concerns include mites, scale, rosy apple aphid, tarnished plant bug, green fruit worm, oriental fruit moth, obliquebanded leaf roller and black stem borer. More in-depth information can be found by watching the latest weekly fruit meetings for southern Michigan (these may take a few days to upload after the Monday meetings). The E-154 guide can be purchased on the MSU Extension Bookstore.
Black stem borer: Main control is to target emerging females as they search for new sites to deposit eggs, which should be in the coming weeks.
Green fruit worm: If necessary, use a broad spectrum insecticide like Grandevo before or after bloom in apples and stone fruit.
Mites: Treatment begins after petal fall.
Oriental fruit moth: It is time to think about mating disruption before emergence.
Pear psylla: We passed the time for early control with dormant oil. Later on, control requires reducing vegetative flushes and hand removing suckers.
Plum curculio: Active during bloom but not on fruit, which is where damage is. Plum curculio management is usually done at petal fall because most sprays for plum curculio are also toxic to bees. Options for management include contact pesticides to kill feeding adults, pyrethroids or Avaunt (non-contact poison, ingestible). At five to seven days post-petal fall, there is enough of a fruitlet for oviposition, so neonicitinoids can be applied as an oviposition deterrent. In stone fruit, the neonicitinoids can be applied at shuck split. Nothing should be applied before bloom (no fruit) and nothing should be applied during bloom to protect pollinators.
Redbanded leafroller: Flight detected at the Trevor Nichols Research Center in Fennville, Michigan.
Rosy apple aphid: Check for colonies in fruit clusters when we get to the pink stage. If necessary, use a pre-bloom insecticide for control.
San Jose scale: We are past the time for early season dormant oil applications. The next opportunity to control them is during their crawler stage around the second cover in apples.
Spotted tentiform leafminer: Flight detected at the Trevor Nichols Research Center in Fennville.
Tarnished plant bug: These are usually present on orchard floors, though they tend not to be a major issue. Pyrethroids are the most effective pink stage spray. The tarnished plant bug can damage flowers and developing fruit. Do not apply anything during bloom.
Seasonal weather update
With the cool temperatures, our growing degree day (GDD) accumulation has continued to slow and the bring us closer to the five-year average for total accumulation. We have had about an inch of liquid precipitation in the last week (see table below). We have had lows that have cut close to critical temperatures for some crops, but for the most part we have stayed above those temperatures. As always, it will be wise to stay alert to changing weather conditions in the next week.
|
Liquid Precipitation Accumulation Mar. 1 - May 1, 2023, issued May 1, 2023 |
||||
|
Station (County) |
Rainfall Total (in.) Current |
Hours with Rainfall Current |
Rainfall Total Average (5 Yr.) |
Hours with Rainfall Average (5 Yr.) |
|
Commerce (Oakland) |
6.9 |
142 |
4.6 |
107 |
|
Deerfield (Monroe) |
6.2 |
129 |
5.1 |
114 |
|
Emmett (St. Clair) |
7.8 |
141 |
3.6 |
112 |
|
Flint (Genesee) |
7.0 |
131 |
4.5 |
114 |
|
Freeland (Saginaw) |
. |
. |
. |
. |
|
Hudson (Lenawee) |
4.7 |
124 |
5.4 |
125 |
|
Lapeer (Lapeer) |
3.6 |
96 |
4.7 |
108 |
|
Pigeon (Huron) |
5.4 |
104 |
4.3 |
108 |
|
Romeo (Macomb) |
7.3 |
145 |
4.3 |
98 |
|
Average of stations in this region: |
6.1 |
126.5 |
4.6 |
110.6 |
|
Difference in Liquid Precipitation Accumulation from Mar. 1 observed April 24 and May 1, 2023; issued May 1 |
||||||
|
Station (County) |
Rainfall Total (in.) April 24 |
Rainfall Total (in.) May 1 |
Difference from April 24-May 1 |
Hours with Rainfall April 24 |
Hours with Rainfall May 1 |
Difference from April 24-May 1 |
|
Commerce (Oakland) |
5.9 |
6.9 |
1.0 |
111 |
142 |
31.0 |
|
Deerfield (Monroe) |
4.5 |
6.2 |
1.7 |
93 |
129 |
36.0 |
|
Emmett (St. Clair) |
6.6 |
7.8 |
1.2 |
115 |
141 |
26.0 |
|
Flint (Genesee) |
6.4 |
7.0 |
0.6 |
112 |
131 |
19.0 |
|
Freeland (Saginaw) |
. |
. |
. |
. |
. |
. |
|
Hudson (Lenawee) |
3.6 |
4.7 |
1.1 |
94 |
124 |
30.0 |
|
Lapeer (Lapeer) |
3.1 |
3.6 |
0.5 |
73 |
96 |
23.0 |
|
Pigeon (Huron) |
4.6 |
5.4 |
0.8 |
83 |
104 |
21.0 |
|
Romeo (Macomb) |
5.7 |
7.3 |
1.6 |
113 |
145 |
32.0 |
|
Average of stations in this region: |
5.1 |
6.1 |
1.1 |
99.3 |
126.5 |
27.3 |
In the short-term, we are expecting continued rain and cool temperatures through Wednesday, May 3, with warmer and drier conditions coming later in the week.
The long lead outlooks are still calling for warmer and wetter than normal conditions for the late spring and summer seasons.
Our regional average growing degree day accumulation for the season has regressed closer to the five-year average compared to last week, exceeding the average by 29 GDD at 42 F, 26 GDD at 45F and 25 GDD at 50 F (see table below). Read this Michigan State University Extension article to learn more about degree days: Understanding growing degree-days.
|
Degree Day Accumulation Mar. 1 - May 1, 2023, Forecast from May 1-May 7, 2023; issued May 1 |
|||||||||
|
Station (County) |
Degree Days Base 42 F Current |
Degree Days Base 42 F Average (5 Yr.) |
Degree Days Base 42 F Forecast |
Degree Days Base 45 F Current |
Degree Days Base 45 F Average (5 Yr.) |
Degree Days Base 45 F Forecast |
Degree Days Base 50 F Current |
Degree Days Base 50 F Average (5 Yr.) |
Degree Days Base 50 F Forecast |
|
Commerce (Oakland) |
250 |
230 |
299 |
186 |
168 |
223 |
116 |
93 |
138 |
|
Deerfield (Monroe) |
306 |
290 |
355 |
227 |
214 |
263 |
136 |
125 |
156 |
|
Emmett (St. Clair) |
245 |
216 |
287 |
183 |
157 |
213 |
113 |
86 |
129 |
|
Flint (Genesee) |
294 |
265 |
343 |
222 |
197 |
259 |
139 |
112 |
161 |
|
Freeland (Saginaw) |
242 |
209 |
289 |
180 |
152 |
214 |
112 |
84 |
131 |
|
Hudson (Lenawee) |
270 |
255 |
319 |
201 |
189 |
238 |
124 |
109 |
146 |
|
Lapeer (Lapeer) |
274 |
241 |
319 |
206 |
178 |
240 |
129 |
102 |
148 |
|
Pigeon (Huron) |
236 |
176 |
273 |
178 |
126 |
203 |
115 |
68 |
126 |
|
Romeo (Macomb) |
261 |
236 |
308 |
195 |
170 |
229 |
118 |
93 |
137 |
|
Average of stations in this region: |
264 |
235 |
310 |
198 |
172 |
231 |
122 |
97 |
141 |
|
Difference in Degree Day Accumulation from Mar. 1 observed Apr. 24, and May 1, 2023; issued May 1 |
|||||||||
|
Station (County) |
Degree Days Base 42 F April 24 |
Degree Days Base 42 F May 1 |
Degree Days Base 42 F Difference |
Degree Days Base 45 F April 24 |
Degree Days Base 45 F May 1 |
Degree Days Base 45 F Difference |
Degree Days Base 50 F April 24 |
Degree Days Base 50 F May 1 |
Degree Days Base 50 F Difference |
|
Commerce (Oakland) |
225 |
250 |
25 |
171 |
186 |
15 |
111 |
116 |
5 |
|
Deerfield (Monroe) |
271 |
306 |
35 |
205 |
227 |
22 |
128 |
136 |
8 |
|
Emmett (St. Clair) |
220 |
245 |
25 |
169 |
183 |
14 |
109 |
113 |
4 |
|
Flint (Genesee) |
263 |
294 |
31 |
203 |
222 |
19 |
133 |
139 |
6 |
|
Freeland (Saginaw) |
213 |
242 |
29 |
162 |
180 |
18 |
106 |
112 |
6 |
|
Hudson (Lenawee) |
242 |
270 |
28 |
183 |
201 |
18 |
118 |
124 |
6 |
|
Lapeer (Lapeer) |
246 |
274 |
28 |
189 |
206 |
17 |
124 |
129 |
5 |
|
Pigeon (Huron) |
208 |
236 |
28 |
163 |
178 |
15 |
110 |
115 |
5 |
|
Romeo (Macomb) |
235 |
261 |
26 |
178 |
195 |
17 |
113 |
118 |
5 |
|
Average of stations in this region: |
236 |
264 |
28 |
180 |
198 |
17 |
117 |
122 |
6 |
Watch Jeff Andresen's Biweekly Agricultural weather forecast reports.
More information and reports on normal weather conditions and departures from normal can be found on the NOAA Climate Prediction Center website, NOAA U.S. Climate Normals website, NOAA Climate Normals Quick Access Page (which may be searched by region), and Midwest Regional Climate Center website.
