Michigan vegetable crop report – May 1, 2024

Asparagus picking has turned on. More field work and plantings continue.

Asparagus coming up from below the ground.
Monday (April 29) spear pics from eastern Oceana County. Emergence was variable with some fields having sizeable spears, but others just popping. Harvest is expected to ramp up through the weekend. Photo by Ben Werling, MSU Extension.


For the past week, the state saw temperatures up to 4-5 degrees Fahrenheit above-normal with variable precipitation. There were isolated areas with large hail in northern lower Michigan. Growing degree day (GDD) totals are several to 14 days above-normal. Soil temperatures are warming following warmer air temperatures, with warming roughly a week ahead of normal.

This week’s forecast features:

  • Rainfall totals of 0.75 inch to over 1 inch are forecast through next Wednesday, May 8, with most expected to fall overnight next Monday into Tuesday.
  • Breezy with scattered showers to the north, variably cloudy to the south Wednesday, May 1. Increasing clouds Thursday with showers developing west to east by evening and continuing into Friday. Scattered rain is possible again this weekend Saturday and Sunday, and again Monday and Tuesday of next week.
  • High temperatures from the mid-50s north to mid-70s south Wednesday, warming to the upper 60s in the north to upper 70s in the south Friday and continuing through this weekend. Low temperatures warming from the 30s in the north to upper 40s Thursday morning to the upper 40s north to mid-50s south Friday and continuing through the weekend.
  • Elevated GDD accumulations and potential evapotranspiration (PET) rates (up to 0.20 inch per day) through next week, especially to the south.
  • Medium range outlooks generally call for above normal mean temperatures and precipitation totals the next one to two weeks.

Crop updates

Herbicide label updates

Check out this article about new and renewed herbicide labels for vegetables in 2024, including Optogen, Rely and Reflex.

Irrigation: Check all systems go!

Now is a great time to make sure irrigation systems like center pivots are working, especially given delays and shortages in materials. Here are some helpful articles on pivot startup and other “pivotal” topics.

Vegetable transplants

Greenhouses are full of vegetable transplants ready for field planting or retail sales. 

With overcast skies, greenhouse conditions can cool down, slowing evapotranspiration of growing transplants. Not adjusting watering schedules can lead to cool, wet soils which can harbor diseases that affect seedlings. Insect and mite activity may rise in the greenhouse, particularly when vents are opened during the warm and sunny days. 

Updated recommendations for managing diseases and insects have been released by Michigan State University Extension just in time for the 2024 greenhouse season. Annual updates to the guide are made by MSU Extension specialists and colleagues across the country who conduct research trials to assess the efficacy of pesticide products against common greenhouse insects and diseases. An updated 2024 greenhouse disease management fact sheet was released by Michigan State University (MSU) Extension vegetable pathologist Mary Hausbeck. 

In addition, Hausbeck and colleagues developed a list of registered disease management products for vegetables and herbs. The guide provides information such as active ingredients, name of the product, FRAC code, restricted-entry interval (REI) and crop groups and diseases. MSU Extension released a similar list of registered products for greenhouse insect pest management


Boxes, lugs and anticipation were flowing Monday, April 29, in west central Michigan with harvest expected to ramp up through this weekend. Harvest has already begun in southwest Michigan. Thankfully, most asparagus were still tucked in during the freeze last Thursday morning.

White cutworm is the first but very sporadic insect pest of the season. It overwinters as a caterpillar and is ready to go once spears emerge. Look for chewing damage to the tips, then dig around the base of spears to “confirm the worm.” Permethrin (one-day preharvest interval, or PHI) is effective where there are issues. Chlorpyrifos is legal to use this year.

White cutworm larva and damage to asparagus.
White cutworm overwinters as a caterpillar and feeds at night on spear tips. It is a very sporadic early season pest, historically controlled by chlorpyrifos. Spear tips can also get nicked by mowers, so dig around the base of damaged spears  to look for worms in the soil where they hide out in daytime. Photo by Ed Grafius.

It can be difficult but important to balance harvest with fungicide applications to newly planted fields. In the coming weeks, young plantings that will not be harvested should be scouted for evidence of aecial lesions of the rust pathogen (Puccinia asparagi). These lesions are oval, light orange, at first raised, with lesion centers becoming sunken as the lesions age. Air currents and splashing rain carry the yellow aeciospores from the lesions to other fern branches and needles where they germinate and cause new infections when free moisture is present.

Rust and purple spot on asparagus.
Scout young fields for rust aecial lesions (white arrow) as they fern out. They are bright orange and blistered above the stem surface. By contrast, purple spot lesions (red arrow) are flat and dark purple. Photo by Ben Werling, MSU Extension. 

The aecial stage of rust is most abundant in April and May. However, if the shoots are harvested, rust does not have an opportunity to develop. In young plantings where the spears/stalks are not harvested, the aecia develop, providing spores for new infections, and thereby continue the rust life cycle. The next stage of the rust life cycle that will occur is the repeating or uredial stage. Urediospores are produced in great numbers and may resemble a reddish dust. They germinate in the presence of moisture and within 12 days may cause infections and yield a new generation of spores.

Although rust lesions affect only the fern, rust reduces the vitality of the entire asparagus plant resulting in slender spear or culls the following year. Rust also increases the plants’ susceptibility to Fusarium crown and root rot. It’s advisable to monitor asparagus fields, especially those newly established and least able to withstand stress and infection, for the rust pustules that may cause premature defoliation. If rust pustules are already present, the first spray should be a locally systemic rust fungicide (e.g., myclobutanil and tebuconazole) because it will provide some control of newly-established lesions and will limit infections that have not yet fully developed.

Protectants (e.g., chlorothalonil and mancozeb) will not impact the lesions already present but will prevent new lesions. Since the rust specific fungicides do not control purple spot, it makes sense to mix a protectant fungicide with a locally systemic rust fungicide to prevent a foliar epidemic on the fern in those young fields that will not be harvested and need to be protected so that they can become fully established. Please note that fungicides are to be applied only to the fern and are not applied to the spears to be harvested.

Brassicas and greens

Transplants of cabbage and other brassicas have been going in since early April. 

Cold damage to cabbage transplants.
Cabbage transplants were hit by cold damage after last Wednesday’s frost in Tuscola County. Photo by Salta Mambetova, MSU Extension. 

MSU Extension is working to test the accuracy of the cabbage maggot degree day model, lining up trap catches with model predictions. Flies are active at west Michigan sites we are monitoring, and eggs were detected on transplanted brassicas this past week. Verimark is consistently effective as a tray drench for this pest. Unfortunately, there are no great insecticide options for controlling it after planting. Row covers that are put on at planting and kept on provide excellent control when possible.

Carrots and celery

Early-planted processing carrots were germinating on the west side of the state this week and are expected to pop soon. Celery transplanting is ongoing. Similarly, in the east side of the state, carrot and celery have started being planted. 

Fruiting vegetables

The Michigan vegetable crop report from April 24 addressed bacterial symptoms and management in transplants. This week, we have some more information and pictures of abiotic issues from things like ethylene, sulfur dioxide and temperature effects. Growing warm-season plants in a greenhouse in the early spring is like operating a space station. There is such a small margin for error in the climate control that tips the balance out of favor. Proper design and routine heater maintenance is important for preventing build-ups of pollutants in the transplant growing space. Each system has its own needs, but some basic maintenance includes checking for and removing creosote buildup in the flue and ash buildup at the air intake gate, installing a flue cap to prevent downdrafts, or sealing firebox doors with rope gaskets and flue pipe connections with gasket cement.

Sulfur damaged to plants
Sulfur dioxide damage at the base of tomatoes and cucumber. This gas is heavier than air and sinks to the bottom of the space. On the left, the plant is also exhibiting ethylene injury at the top of the plant. Photos by Ben Phillips of MSU Extension and Beth Hubbard of Corey Lake Orchards.
Ethylene damage and flue pipe.
Ethylene injury in tomato from a leaky wood-fired furnace inside the greenhouse. The leaky spots look greasy in this photo. In addition, the lack of a flue cap can push gasses back into the firebox and out of any leaky spots like these. Photos by Ben Phillips, MSU Extension.
Green tomato fruit.
Abnormal fruit development, like catfacing (left) and zippering (right), is often a result of low temperatures at bud formation and post-pollination flower drop. Raising high quality tomatoes in early spring is a difficult task, made easier with automation for vent and furnace controls. Photo by Ben Phillips, MSU Extension.

Onions and garlic

As sowing wraps up, onion transplants were going out over the past week on farms big and small. Sown onions were emerging and growing, and previously planted sets and transplants were pumping out leaves. 

Onion transplants.
Some handsome onion transplants ready to go out late last week. Photo by Ben Werling, MSU Extension.

Fall-planted garlic is up to 7 or 8 inches tall now in some areas. 

Garlic plants.
Garlic crop in Midland County on April 17. Photo by Salta Mambetova, MSU Extension.
Loop stage of onion.
Loop stage of onion in Lapeer County. Photo by Salta Mambetova, MSU Extension.

Root crops and potatoes

Root crops are up and have been at a standstill, but are starting to grow now with the moisture and warmer weather. 

Of course, weeds will start to grow too! Turnips and weeds were at an ideal stage for mechanical weeding at one location this week. A number of manufacturers have developed steerable or camera guided toolbars that allow growers to weed right up to the row, and use in-row weeding tools. These take some fine tuning and experimentation to kill weeds without injuring crops, but can be effective. They are something to consider for this crop group where there are limited herbicide options available. 

Weeds growing up from ground.
It was gratifying to see growers going after these tiny lambsquarters with weeding tools this week (die weeds die!). The turnips are slightly larger than the weeds, and the lambsquarter seedlings are smaller. Hopefully a good setup for getting ahead of the weeds. Photo by Ben Werling, MSU Extension.

For brassica root crops, cabbage maggot flies were active at locations MSU Extension is monitoring. Egglaying had begun at two locations, though eggs were only detected on large, volunteer turnips and transplanted cauliflower. Post-plant applications of insecticides could begin as sown crops get larger, roots swell and plants become more attractive to flies. Weekly, broadcast applications of the pyrethroid Mustang Maxx provided some suppression in past trials in turnips, but did not provide standalone control. Hero is a combination of the active ingredient in Mustang Maxx, zeta cypermethrin, and bifenthrin. It has a longer PHI than Mustang Maxx. It could be a product to consider. To be optimally effective, insecticide needs to reach soil around the plant base where flies lay eggs. Banded applications are something to consider, as they allow product to be concentrated into a narrower area where the pest is active. Band width can be adjusted to minimize “misses” as the sprayer moves and row spacings change slightly, from planter pass to planter pass. 


Flowers have emerged. With the frost last week, many growers used overhead irrigation to protect open blooms. Irrigation for frost and the on-off rain we have been having can make it so that fungicides have a hard time sticking. If sprays are needed, use systemic options and treat early in the morning for the most time for the plant to absorb the fungicide before the next watering. With bloom and bee activity, do not use insecticides. Cool, wet conditions can favor angular leaf spot, a bacterial disease. The only effective bacterial controls are copper formulations. Growers are looking at early season herbicides to control overwintering weeds and have begun spreading straw. When selecting an herbicide, check the preharvest interval.


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.

Did you find this article useful?