First Fast Fonz Facts Of The 2026 Field Crops Season

May 06, 2026

By Chris DiFonzo and Monica Jean

The 2026 season has kicked off and so have the insects! With the recent weather, moths are starting to blow in from the south and the Michigan State University Extension field crops team has been busy trapping for insect numbers in order to keep you updated. The following are updates and observations from MSU field crops entomologist Chris DiFonzo, PhD.

Tweaks to the MSU field crops insect management guide

The MSU field crops insect management guide was updated and handed out at winter meetings. An additional update will be added online to include the new insecticide isocycloseram in the corn and soybean sections. There is also an organic version available now.

Alfalfa weevil larval feeding

Alfalfa weevil larval feeding has started in southern counties. The growing degree-day (GDD) total, using base 48 degrees Fahrenheit, since Jan. 1 is useful to predict egg hatch (300 GDD), feeding by small (301-438 GDD) or large (439-595 GDD) larvae, and the start of pupation (greater than 596 GDD). Here are GDD totals and predicted alfalfa weevil stages at representative sites in south and central counties as of April 29:

Eggs haven’t hatched yet in St. Clair County (225 GDD), Ithaca (278 GDD) or Kinde in the Thumb (156 GDD).
Small larvae and light feeding are present in Allegan (373 GDD), East Lansing (330 GDD) and Monroe County (311 GDD).
Fields in Cassopolis (414 GDD) and Coldwater (399 GDD) are close to transitioning to larger larvae and more feeding, although the current cooler weather pattern will slow things down.

It’s easy to track weevil development closer to your location. Simply choose a nearby Enviroweather station at mawn.geo.msu.edu. Under the “Custom reports” drop-down menu, pick “Growing Degree-Day Data.” In the table that pops up, be sure to set the base temperature to 48 and the start date as Jan. 1. Then hit “Generate Report” to generate a table of GDDs by date. Scroll to the bottom of the output for the GDD total, under the column BKEM-SUM. If you have any problems doing this, email me at difonzo@msu.edu and I can send something that’ll help walk you through it.

Do not spray based on the model output! The model simply predicts the stage of the population based on local GDDs, but it doesn’t tell you if or how many larvae are present. Scout field to be sure larvae are present and feeding. A quick threshold is 40% of stems with feeding, based on assessing at least 100 stems across a field. If you are within 10 days of cutting, early harvest is much preferred to keep weevil parasitoids in your fields. Alfalfa fields also produce numerous beneficial insects that move into neighboring corn and beans later in the season.

A spike in true armyworm trap catches

True armyworm trap catches spiked in sporadic locations as moths move on weather fronts from south to north. The Ohio State University trapping network reported high trap catches for the last two weeks in northwest Ohio. In southwest Michigan, MSU Extension field crops educator Nicolle Ritchie reported 125 and 83 moths over the last two trapping periods.

Source : msu.edu

Video: Turning Plant Defense Into a Management Strategy

Turning Plant Defense Into a Management Strategy

Understanding how a plant responds to stress is one thing.

Using that knowledge to make better management decisions is another.

Systemic acquired resistance, or SAR, is the plant's more direct defense response. When stress or infection occurs, the plant begins signaling throughout its system and preparing defensive compounds.

But if we know that response exists, can we help prepare the plant before the stress arrives?

The answer starts with understanding what triggers the response and what the plant needs to carry it out.

The Trigger and the Fuel

Salicylic acid plays an important role in triggering the SAR pathway.

Think of it as turning the truck on.

The engine may be running, but it still needs fuel to do the work.

In this case, manganese plays an important role in supporting the enzyme systems involved in the plant's defensive response.

This makes manganese status an important part of the conversation. Whether a producer is using tissue testing, sap analysis, or simply scouting for visible deficiency symptoms, the goal is to make sure the plant has adequate manganese available.

Manganese is required in relatively small amounts, but that does not make its role small.

If the plant receives a signal to defend itself but lacks the nutrition needed to support that response, it may struggle to carry out the process efficiently.

The trigger matters.

The fuel matters too.

Prepare Before the Stress Arrives

The best time to think about stress management is before the plant is overwhelmed.

Once a crop is already struggling, management can quickly turn into a game of catch-up.

This is similar to nitrogen management. Once a plant becomes severely deficient, correcting the problem does not necessarily erase the time and yield potential already lost.

Plant defense can work the same way.

Low-rate, targeted approaches designed to support the SAR pathway may fit best ahead of an expected stress event rather than after significant damage has already occurred.

That requires producers to think about predictable stress.

We may not know exactly what the weather will do tomorrow, but we generally know summer heat is coming. We know certain field conditions increase disease pressure. We know a herbicide application can temporarily stress a crop as the plant processes the chemistry.

Even a properly timed and labeled herbicide application can create a temporary response in the plant.

That does not mean the herbicide is bad.

Weeds can create significantly more yield loss than the temporary stress caused by controlling them.

The question is not whether we should eliminate every stressor.

The question is whether we can better prepare the plant to manage necessary and predictable stress.

Not All Stress Is Bad

Stress is a normal part of plant growth.

A perfectly stress-free environment does not exist in the field.

In fact, some stress is necessary for normal plant development. A plant responds to wind, temperature, moisture, sunlight, and countless other environmental signals throughout the season.

The environment is stress.

The plant's job is to manage it.

Problems begin when the stress load becomes greater than the plant's ability to respond.

Extreme heat, drought, high salt concentrations, disease pressure, and even certain management practices can add to that load.

This is where understanding SAR becomes useful.

Instead of waiting until the plant is visibly struggling, producers can begin identifying periods when stress is likely and make management decisions around those windows.

ISR Starts With the Soil

While SAR is a more direct defense response, induced systemic resistance, or ISR, brings the conversation back to soil health.

The longevity of a farm is closely connected to the health of its soil.

Carbon plays a major role because it supports biological life within the soil. Bacteria, fungi, and other organisms interact with plant roots and influence how the plant grows, accesses nutrients, and prepares for stress.

This is why soil health cannot be reduced to one product or one application.

It is a system.

Keeping living plants in the field longer can support biological activity. Cover crops may fit some operations. Better water management can improve soil conditions.