MSU Extension Fruit & Nuts

Welcome to the fourth in-season fruit article update for southeast Michigan for the 2024 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

Many growers are still evaluating the extent of the damage from the April 24-25 frost, as it is not always immediately apparent what has survived and what hasn’t. For information on assessing frost damage please read the MSU Extension article “Assessing frost and freeze damage to flowers and buds of fruit trees.” While we are not expecting frost in the coming week or the rest of the season, there is potential for severe weather, including hail, overnight on Tuesday, May 7. It would be helpful to brush up on storm responses by reading this 2016 MSU Extension article on responding to severe weather. We expect cooler temperatures as we approach the weekend with scattered rain events throughout the week. 

In the last week we have seen warmer temperatures than normal, and we are well ahead of previous years on growing degree day accumulation. Most tree fruits have wrapped up blooming in warmer parts of the region, while blueberries have entered full bloom. Read this article on pollinator stewardship, which is always of paramount concern during bloom. The primary message is not to spray products that could be harmful to pollinators during bloom when pollinators are active. 

We are expecting a few rain events this week, and with those come increased risk for fungal infections like apple scab and bacterial infections like fire blight. Fire blight can continue to pose a risk even in a year with crop loss because shoot blight can kill the entire tree. Using programs implementing Apogee and Actigard or antibiotic sprays can continue to protect your orchard. You can see you an overview of disease risk on the RimPro interactive location chart. Make sure to check the models frequently as they change with weather forecasts. 

Local scouts in southeast Michigan have reported increased catches of oriental fruit moth, plum curculio, and woolly apple aphids. Codling moth males have been caught in northern Ohio and Fennville, Michigan. The trap line report at the Trevor Nichols Station in Fennville also indicated the flight of San Jose scale males in addition to catches of grape berry moth and cranberry fruit worm.  

Many of you will have already done spring weed control, but if not, this 2020 MSU Extension article on spring herbicide applications lists some available options. 

I encourage our growers to attend the weekly southern Michigan grower meetings virtually on Monday evenings by registering on our event page. 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 Media Space (these may take a few days to upload after the Monday meetings). 

Fruit-by-fruit conditions

Apples

Many apple cultivars are at petal fall with setting fruit at the MSU Tollgate Farm in Novi, Michigan. Lingering bloom can be seen around orchards in Romeo and Fenton, Michigan, but most cultivars are at petal fall. We are still in primary scab season. RimPro is currently reporting a risk of a scab infection events on May 8, 9, 10 and 12. With warm temperatures and wet conditions there is also a high risk for fire blight infections during those same periods. Read this 2020 article from George Sundin for fire blight management options.  

Blueberries

We are in full bloom in blueberry plantings in Fenton, Michigan. 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. Cranberry fruitworm has also been caught on the west side of the state. The critical temperature for damage for blueberries in full bloom is 27 F. 

Brambles

We are seeing floral buds in summer red raspberries at sites in Fenton and Romeo, Michigan. Watch out for orange rust and raspberry sawfly. 

Cherries

We are seeing fruit set in both sweet and tart cherries in Fenton and Romeo, Michigan. Sometimes the shuck can provide some frost protection if it is still on, but damage was observed in both sweet and tart cherries. There is a moderate risk of cherry leaf spot infection on May 8. 

Grapes

We are seeing shoot growth up to three inches in Concord grapes in Fenton, Michigan. The region seemed to largely escape frost damage in grapes. 

Strawberries

We are seeing blooms in field strawberries in Fenton and Romeo, Michigan. Early season fungicides should focus on controlling leaf spot. 

Peaches and nectarines

Peaches in Fenton and Romeo, Michigan are at petal fall and fruit set. Peaches seem to have been hit hardest by the frost event. The next chance to control brown rot will begin three weeks prior to harvest.  

Pears

Pears observed in Fenton, Michigan were at fruit set. Pear is susceptible to fire blight, so continue to watch models. 

Plums

European plums in Fenton, Michigan are at fruit set. The critical period for most fungal control is from petal fall to late June, but for brown rot specifically, the critical times are during bloom and later on at fruit coloring. 

Insect conditions

With many fruits at petal fall we are looking at petal fall sprays and moving into first cover, but if your crops are still blooming remember to prioritize pollinator protection. In tree fruit our insect concerns include codling moth, tarnished plant bug, San Jose scale, oriental fruit moth, and oblique banded leaf roller. In small fruit, grape berry moth, raspberry sawfly and cranberry fruit worm are of concern. More in-depth information can be found by watching the latest weekly fruit meetings for southern Michigan on MSU’s Kaltura Media Space (these may take a few days to upload after the Monday meetings). 

Black stem borer. Main control is to target emerging females as they search for new sites to deposit eggs, which starts around 100 GDD50. In warmer parts of the region this window has shut but there may still be time on cooler areas. 

Codling moth. Codling moth has been caught in Fennville, Michigan and Northern Ohio, but not in Southeast Michigan. We expect biofix to happen soon. There is still time to use mating disruption, as the next control point comes at 100-200 GDD50 after biofix with the use of selective ovicidal products. 

Cranberry fruitworm. Scouts in the state have caught cranberry fruit worm. See the linked fact sheet for more information.  

Grape berry moth. Grape berry moth has been caught, but control is usually most effective in the second and third generations. See this early season grape berry moth management article. 

Green fruitworm. Catches are on the decline. These can be controlled with insecticides post-bloom. 

Oriental fruit moth. We are at the last spring control point for oriental fruit moth, which is from 170-195 GDD45 at 10-15% egg hatch. Warmer parts of the region may be past this point. 

Plum curculio. Plum curculio has been caught in cherries in South Lyon, Michigan. In warm conditions like the ones we are experiencing, adults move from overwintering sites into orchards. Watch especially in areas near woods or hedgerows. Products that work primarily as feeding killers can still be used in apples, while those that work as oviposition deterrents and feeding killers can be used in cherries at this point (and apples in the next week or so). 

Raspberry sawfly. Adults emerge in the spring and lay eggs on leaves before bloom. Larvae feed on the leaves. 

Redbanded leafroller. Flight detected at Fennville station. 

San Jose scale. While we are not yet at the crawler stage, products like Movento that induce a systemic response in plants need time to work and can be applied ahead of the crawler stage. San Jose scale males have been caught in Fennville, Michigan, which is an indicator that the crawler stage is coming soon. 

Spotted tentiform leafminer. Catches in Southeast Michigan remain low and are decreasing. 

Tarnished plant bug. You should avoid mowing until after bloom when you can use insecticides because mowing can cause the tarnished plant bug to move from the orchard floor to feed on flowers and developing fruit.  

We have moved past the control periods for pear psylla, rosy apple aphid, mites, green fruit worm, and black stem borer. The control window for oriental fruit moth is closing. 

Disease conditions

Apple scab. We are in primary scab season. RimPro is currently reporting a risk of scab infection events on May 8, 10, and 12 in the region. Early control of scab is important for reducing secondary scab infections that can affect fruit. 

Black knot. There is still time to prune out and burn black knot in plums and sour cherries. Fungicides may be used for limited control to supplement pruning and sanitation efforts. 

Brown rot. This disease affects stone fruit and can proliferate during bloom. The next chance to control is about three weeks before harvest when fruits start to color. 

Cherry leaf spot. We expect moderate risk of infection on May 8. See this 2013 article on cherry leaf spot management. 

Fire blight. We expect high risk for fire blight this week, especially in areas with continued apple bloom. Monitor RimPro, Enviroweather and IPM updates for spray timing. Read this 2020 article from George Sundin for fire blight management options. 

Grape black rot. There is potential for conidi infection on May 8. See this 2014 article for grape black rot management options and consult E-154. 

Mummy berry. Southwest Michigan scouts report apothecia showing up. See E2846 for control methods. 

Orange rust. With our advanced growing degree days this year we are hitting the risk period for orange rust in brambles early. Read the linked article for control options. 

Peach leaf curl. If symptoms are starting to appear, control needed to be done before bud break. The next chance to control it will be with fall sprays. 

Phomopsis. In blueberries, the Phomopsis fungus is active from bud swell until after harvest. 

Powdery mildew of apple and pear. You can start to include products labeled for powdery mildew in sprays starting at tight cluster. 

Powdery mildew and downy mildew of grape. Scouting should start early for these diseases. Read the linked article for control options. 

Seasonal weather update

In the last week, southeast Michigan has seen an average of over 10 hours of rain accumulating to 0.4 inches of precipitation and we are ahead of the five-year average in both time and amount of rainfall. 

 In the short term, we are expecting thunderstorms to develop overnight Tuesday evening. Scattered showers will be seen Wednesday night into Thursday. Friday will be dry and fair and the weekend will see cooler temperatures with scattered showers. Temperatures will hit highs in the upper 70s Tuesday and Wednesday while lows are expected in the 40s over the weekend.  

In the medium term we are looking at above normal mean temperatures and precipitation totals. The long lead outlooks are still calling for warmer than normal conditions for the late spring and summer seasons with normal precipitation levels. 

Our regional average growing degree day accumulation for the season are ahead of the 5 year average by 201 GDD at 42 F, 164 GDD at 45 F, and 106 GDD at 50 F (see table below). This puts us at one to two weeks ahead of normal in most of the region. Read this Michigan State University Extension article to learn more about degree days: Understanding growing degree-days. 

Watch Jeff Andresen's Biweekly Agricultural weather forecast reports here. 

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.