Cooperative Extension at Highmoor Farm

Garlic IPM Newsletter No. 9 — June 12, 2025

Garlic can be categorized as either softneck and hardneck varieties. Hardneck garlic tends to be more cold hardy, so these varieties are more commonly grown in Maine than softnecks. They have larger but fewer cloves per bulb, and are usually easier to peel.

The term “hardneck” refers to the false flowering stalks that these types form, giving the bulbs a hard central neck. This provides one of the great perks of growing garlic in New England – garlic scapes! Scapes are forming at scouting locations in southern Maine now, and should be ready for harvest within the next week or two.

As scapes grow, they will form a curly cue shape, and then straighten back out to point upright if left on the plant. To harvest them, wait until fully curled, and then clip right below the curl. While an umbel containing bulbils will otherwise eventually form at the end of the scape, these are far inferior for planting than actual cloves.

So, should you harvest scapes?

Harvesting scapes has been found to improve bulb size, as it diverts plant energy from “seed” production at the end of the scape to bulb development. That said, the degree to which yield is improved is variable (commonly 15-20%) and so may not always be worth the labor. In the home garden, harvesting scapes makes sense. For commercial farms, harvesting scapes can be worthwhile if there is a market for them. If there is no market or use for the scapes, weighing the harvest labor against the potential yield increase to find the most economic option is recommended.

Pest Situation

Onion thrips were found at all scouting locations this week, which was right on time according to the phenological model (140 GDD_52.7). All locations were well under the threshold of 1 to 3 per leaf, but populations are expected to increase soon with the warmer weather this week and next. Now is the time to be sure you have appropriate control products on hand.

In Maine, all locations except Cutler and Katahdin have accumulated sufficient growing degree days for thrips to emerge. As a reminder, scout for thrips by closely inspecting leaf folds, along midveins, and where leaves meet. The first thrips of the season are adults and therefore tend to be darker in color. You may also see some feeding injury, which appears as white, streaky scarring.

Despite favorable conditions, the spread of botrytis leaf blight within scouted fields has slowed in recent weeks and new growth is generally healthy with lesions under the 1 per leaf threshold.

Older leaves are beginning to die back, which is normal, but it can sometimes be difficult to distinguish between healthy and diseased dieback. This is often made more confusing because the senescing foliage is especially vulnerable to infection, but opportunistic fungi and bacteria may not be pathogenic. Yellowing should begin at the oldest leaf tip and progress down the leaf without the appearance of sooty-looking spores or lesion patterns. It may be worth submitting leaves with “dirty” tips to the UMaine Plant Diagnostic Lab, as even the earliest Maine garlic still has about a month left in the field.

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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