Michigan vegetable crop report – May 29, 2024

Initial harvests are coming off while planting and pest management continue.

Cilantro and dill growing in a field.
Photo by Salta Mambetova, MSU Extension.


Temperatures were 2-6 degrees Fahrenheit above-normal for the past week, prior to cooler weather moving in. Rainfall was variable, with the middle Upper Peninsula and northwest lower receiving high totals and lower totals to the south and east. Degree day totals (base 50 F) are close to slightly above normal in the Upper Peninsula with totals one to two weeks ahead moving to the south. Soil temperatures have fallen off a bit with recent cool weather but are still warmer than normal for the time of year. Soil moisture has been highest to the north, decreasing to the south.

This week’s forecast features:

  • Scattered showers possible Wednesday, May 29, to the south. Partly to mostly sunny and cool elsewhere. Fair and dry Thursday and Friday with a warming trend. Scattered showers possible again Saturday through Monday.
  • Precipitation totals of 0.5 inch or less through next Wednesday.
  • High temperatures in the mid- to upper 60s Wednesday, warming to the 70s by Friday and to the low to mid-80s by early next week. Low temperatures in the 30s and low 40s Thursday morning with scattered frost possible to the north. Lows warming from the 40s Friday morning to the upper 50s to low 60s by early next week.
  • Normal to above normal daily PET rates expected this week (mean daily values from 0.16-0.18 inch).
  • Medium range outlooks generally call for a return of warmer and wetter than normal weather by next week.

NOTE: There will be no Michigan vegetable report next week as the team will be leading a tour for visiting growers from Ukraine. If you have any questions, please reach out to the vegetable educator in your region.

Agritourism survey 

The 2024 National Agritourism Survey is now collecting responses. All agricultural operations that welcome visitors—whether for on-farm direct sales, educational programs, entertainment, farm stays, recreation, special events and more—are invited to complete the survey.  

By participating in this survey, you'll help us pinpoint the types of support farmers like you require—whether it's getting business assistance, developing networks, applying for grants or navigating zoning and liability issues.  

If you have questions about this survey, please contact Claudia Schmidt, Penn State Extension specialist, at cschmidt@psu.edu. 

National Agritourism Support System Survey | Qualtrics Survey 

Produce Food Safety On-Farm Readiness Reviews 

On May 2, the U.S. Food and Drug Administration (FDA) released their final revisions to the Food Safety Modernization Act Produce Safety Rule Pre-Harvest Agricultural Water Rule. If you are a grower in Michigan, this is a great time to schedule an On-Farm Readiness Review (OFRR). Not only can our team help you assess your on-farm produce safety risks, we can help you assess your water system in light of the updated water rule. If you have already had an OFRR on your farm, no problem, we are happy to come back out to help you assess your water system based on the new parts of the water rule. 

An On-Farm Readiness Review (OFRR) is an opportunity for a grower to walk around their farm with their local conservation district produce safety technician and a produce safety specialist from Michigan State University Extension. These 2-hour educational visits take place during the harvest season and are meant to be casual and low stress. Everything discussed during an OFRR is confidential and focused on ways a grower can reduce their own risks in relation to produce safety. There is no pressure to take our advice either, we are just here to support you in your produce safety efforts!  

Crop updates 


Growers are considering making a first fungicide application to 2-year-old asparagus plantings as fern begins to develop. Chlorothalonil, azoxystrobin and mancozeb can all help limit purple spot disease on the fern. Tebuconazole is a rust specific fungicide.

Purple spot disease on asparagus spears and fern is caused by the fungus Stemphylium vesicarium. The fungus survives the winter as sexual spores (ascospores) in a sac (ascus) produced in overwintering structures (pseudothecia) that appear as small black dots on asparagus debris from the previous season. The ascospores are released from the ascus by rain and can be carried by the wind to newly emerged asparagus plants where they cause the first infection of the growing season. These new infections result in spores (conidia) which in turn can cause secondary infections, a process that is repeated as long as temperatures and rainfall are favorable.

Why is purple spot worse during cool, wet periods? Past work by the Hausbeck lab at Michigan State University showed spore release from dead fern residue on the soil surface coincides with rainfall. This is because the overwintering structures produce ascospores in chambers that rely on water pressure to propel them. They swell with rainfall, causing discharge of the spores which can then infect spears. Cool weather exacerbates issues because spears are in the field longer before being picked (it takes longer for them to get to harvestable length). This gives the pathogen more time to produce the symptoms that make spears unmarketable. Lesions on spears are often found on the windward side because blowing sand causes wounding which favors infection. During wet years, spotting can occur on 60-90% of the spears and may result in rejection of the crop, especially for fresh-market sales.

Purple spot also occurs on the asparagus ferns, including the main stem, secondary branches and needles (cladophylls). It’s especially important to protect young plantings that haven’t been harvested for the full duration and have begun to develop into fern. Given the frequent rains, this young fern could become infected and develop disease before harvest of the mature fields is concluded. Severe infection of the fern can result in premature defoliation of the plant, which can limit future yields.

Since fungicide sprays cannot be applied to the asparagus spears during the harvest season, it is important that purple spot be limited during the fern growth period that follows the spear harvest period and continues until frost occurs in the fall. A proactive and effective fungicide spray program during the fern growth period can limit the purple spot severity on the spring’s spears the following year by limiting the amount of the purple spot pathogen that is available in the fall to then overwinter on the dead fern.

Purple spot and rust on asparagus plant.
Purple spot (red arrow) and rust aeciospore (white arrow) lesions at the base of asparagus fern. Photo by Ben Werling, MSU Extension.

Brassicas and greens

Transplants of cabbage, broccoli, cauliflower and brussel sprouts have been going in since early April and continue as weather allows. Early planted radishes have been harvested in the eastern part of the state. Scouts in southwest Michigan are trapping diamondback moth and cabbage looper. Caterpillar feeding and swede midge feeding damage is being observed.

Carrots and celery 

Rain has slowed progress in some muck soil areas. For information on aster leafhopper thresholds and aster yellow infectivity risk, check out this recent article from Zsofia Szendrei and consider signing up for the text alert system.



Pickle plantings are underway. On some farms, watermelon transplanting has finished. Many farms are holding off on pumpkins until later. Striped cucumber beetle adults are easily found. Downy mildew spore traps are being deployed this week and data from the network will be available in the coming weeks.

Fruiting vegetables

Blossom end rot is being reported in tomatoes. Blossom end rot is caused by lack of calcium in fruit but is rarely caused by a calcium deficiency in the soil. Calcium moves through the plant with water, so issues with irrigation are typically to blame if you are seeing this disorder. Soils that are too dry or are overly saturated can cause blossom end rot, so maintain consistent watering and also ventilation in greenhouse settings. Excess nitrogen or periods of low relative humidity can also be responsible.


Stemphylium affects onion leaves causing blighting and premature leaf death, which reduces photosynthesis and yield. The Hausbeck lab at Michigan State University has investigated when to begin fungicide applications, how to apply them and what products to select. Their results showed that a fungicide program should be initiated at the three- to four-leaf stage, which is earlier than might be expected. The first fungicide application of the season should be one that is highly effective and is locally systemic within the plant.

Past research has shown that Luna Tranquility or Miravis Prime are among the top choices to consider for the first fungicide application. After this first application, fungicides with a differing mode of action such as Tilt or Omega could be considered for rotation with these highly effective materials. Neither Tilt or Omega may be as effective as Luna Tranquility or Miravis Prime. When using either Tilt or Omega, it could be useful to tank mix them with a full rate of Bravo WS (chlorothalonil). Spray intervals with these products should not exceed seven days. Past research showed that control is reduced as intervals approach 10 days.

A few other notes on product selection and resistance management:

  • Bravo (chlorothalonil) can provide some protection against Stemphylium. Mancozeb has limited activity.
  • The Stemphylium pathogen is no longer controlled by strobilurin fungicides (FRAC 11).
  • Using a highly effective product early and then rotating them with fungicides that belong to other FRAC groups is important for efficacy and resistance management.

Example of fungicides that could be included in a Stemphylium leaf blight spray program and used in alternation.


Active ingredient


Miravis Prime

Pydiflumetofen + fludioxonil


Luna Tranquility

Fluopyram + pyrimethanil








*Consider tank mixing with a full rate of a chlorothalonil based fungicide

An onion growing in a field.
These handsome Highlanders (early variety of onions) were approaching the stage when fungicide applications for Stemphylium could be initiated (the three- to four-leaf stage). Photo by Ben Werling, MSU Extension.

Thrips were present last week in large onion transplants that had been out under row cover, but the first application of Movento was doing its work. There were very few immatures and mostly adults (the product is most effective against immatures). For onion transplants, keep in mind that Movento will be most effective when applied before onions begin to bulb. Two back-to-back applications are helpful when using Movento. A threshold of 0.6 to one thrips per leaf can be used for making decisions about Movento application.

Root crops and potatoes

Hilling is ongoing. Potato leafhoppers are being caught. Colorado potato beetle pressure is high already this spring.


The first strawberries are being picked in eastern Michigan.


First harvest of dill and cilantro are being picked this week in eastern Michigan.  

Cilantro and dill growing in a field.
Fresh herbs anyone? Dill is one of my favorite herbs. Photo by Salta Mambetova, MSU Extension.


This work is supported by the Crop Protection and Pest Management Program [grant no. 2021-70006-35450] from the USDA National Institute of Food and Agriculture. Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture. 

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