Cooperative Extension at Highmoor Farm

Garlic IPM Newsletter No. 1 — April 30, 2026

Garlic crops are off to a healthy start for the 2026 growing season. Rain is in the forecast, which is much needed in areas still under severe drought in Maine, but this may be conducive to foliar pathogens and clove rots. It is time to begin scouting garlic to ensure that any problems are identified and addressed as early as possible.

Maine Mesonet Updates

Installation of the Maine Mesonet, the network of 26 state-of-the-art weather stations around the state, is well underway. Three stations were installed last fall at University of Maine locations (Orono, Highmoor Farm in Monmouth, and Blueberry Hill in Jonesboro), and more are in progress. These weather stations collect high-resolution data for weather forecasts and are also Netwrok for Environment and Weather Applications (NEWA)-compatible, meaning that NEWA tools can now be used to forecast pests and diseases at these additional Maine sites. New stations will be announced in this newsletter as they come online.

How can forecasting tools help you manage pests and diseases?

Plant pathologists often refer to the “disease triangle”, which illustrates that disease only occurs when three things are present simultaneously:

1. A susceptible host plant
2. The pathogen – these may be present in soil or plant residue, or may move into an area via seed, equipment, workers, or weather systems
3. Favorable environmental conditions – many pathogens require specific humidity, moisture, and/or temperature conditions to become active

Insect pest infestations can be thought of in much the same way. Oftentimes, for insect pests, the accumulation of temperature (expressed as growing degree days, GDDs) drives development through their life cycles. To best manage pests and diseases, it is important to 1) scout for their presence, and 2) anticipate when conditions will favor their development.

Pest Situation

No major pests or diseases have been observed in early season garlic scouting throughout southern and central Maine. Stay tuned for future newsletters where the use of forecasting tools for specific pests and diseases will be explained in greater detail.

Early Season Garlic Management

For most in Maine, it is now time to sidedress garlic. The New England Vegetable Management Guide’s section on garlic outlines garlic fertility recommendations. Because garlic overwinters, it is best to split its 120 pounds per acre nitrogen (N) requirement across three applications:

1. Pre-plant: Applying 40 lb. N per acre at this time helps cloves establish root systems while minimizing leaching.
2. At 6-8″ tall tops: In early May, plants can use an additional 40 lb. N per acre for foliar growth as plants develop throughout spring.
3. One month later: The final 40 lb. N per acre sidedress provides a final boost for foliar growth. Do not apply nitrogen after this point (typically early to mid-June) because this can cause foliar growth to continue at the expense of bulb development.

This is also a time when many wonder whether to remove the straw used to mulch garlic over the winter. A sufficiently thick straw layer can reduce weed pressure, but it also may keep the soil cooler and wetter than preferred. Here are some considerations:

• How thick is the straw? Snow and wind can compress and move straw such that it is no longer thick enough in some spots to provide weed control. A solid 3-4″ layer is generally needed to prevent weeds from popping through. Managing weeds coming through straw can be more laborious than having no straw at all.
• How weedy is the field? If weeds have been well managed in the past and few weed seeds are in the soil, mulch may not be necessary. That said, garlic does not compete well against weeds, and incidental injuries to garlic plants while weeding can make easy entry for pests and pathogens.
• How well drained is the soil? Garlic in low spots or heavy soil may benefit from removing mulch to help the soil dry out and warm up more quickly. Continuously wet soil favors disease. On the other hand, straw can conserve soil moisture during dry seasons and reduce soil splashing in heavy rain events.

It is generally advisable to trial changes on a small section of field before diving head on into a new system.

Peyton Ginakes, PhD
Research Associate
University of Maine Cooperative Extension
Highmoor Farm
52 US-202
Monmouth, ME 04259
(207) 933-2100

peyton.ginakes@maine.edu

This project is funded by a Specialty Crop Block Grant through the Maine Department of Agriculture, Conservation, and Forestry. Funding for the Maine 2024 Specialty Crop Block Grant Program was made possible by a grant/cooperative agreement from the USDA Agricultural Marketing Service. Its contents are solely the responsibility of the authors and do not necessarily represent the official views of the USDA.

Where brand names or company names are used, it is for the reader’s information. No endorsement is implied nor is any discrimination intended against other products with similar ingredients. Always consult product labels for rates, application instructions and safety precautions. Users of these products assume all associated risks.

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