Garlic IPM Newsletter No. 8 — June 12, 2026
Thrips numbers were up in Topsham and Washington this week, but down in Buxton and Monmouth, and all locations are below a 1 thrips per leaf threshold. These insect populations thrive in hot and dry conditions, so while this week’s weather may have encouraged their development, the next week of rain and cooler temperatures will probably slow their growth and spread.
| Location | Thrips (per leaf) as of June 16, 2026 |
|---|---|
| Buxton | 0.00 |
| Monmouth | 0.06 |
| Topsham | 0.54 |
| Washington | 0.07 |
When scouting plants for thrips, pay special attention to folded or bent leaf areas, as these protected crevices are where thrips like to hide. Many thrips can accumulate in these small areas; there are at least 20 in the photo to the right. The same is true for leaf axils of onions, where the round hollow leaves meet the neck of plants. A clicker counter is a cheap, handy tool for keeping track when counting small things like thrips or lesions.
Disease Update
Leaf lesions remain levelled off for the time being, though conditions remain broadly favorable for disease development through the weekend. Additionally, we are seeing an increase in the number of necrotic leaf tips with sporulation (“dirty tips”) at all scouting sites – affecting 29% of leaves in Washington up to 68% of leaves in Topsham. As previously mentioned in the June 4 newsletter, there are two pathogens typically responsible for this: Alternaria and Stemphylium. These foliar diseases (purple blotch and Stemphylium leaf blight, respectively) are common and do not directly attack garlic bulbs, although they may cause a reduction in size if infections are severe and early enough to significantly reduce plants’ ability to photosynthesize.
Scape Season
Scape harvest has begun in southern Maine. Scapes emerge in early to mid June and grow into a curl before then straightening out and pointing upward. These can be harvested any time between when they emerge and when they begin to uncurl, at which time they become too woody for eating.
Scapes are false flowering stalks produced only in hardneck varieties of garlic. These are a relic from when garlic produced seed. If left on the plant, scapes will straighten and the umbel at the end will develop small bulbils. While bulbils can technically be propagated, they are not true seed and will not produce high quality garlic until grown and selected over many seasons.
Harvesting scapes has been found to increase the size of bulbs by about 15-20%, by diverting energy from scape growth back to bulb growth. Because harvesting scapes is laborious, commercial growers are advised to factor their market for scapes, scape harvesting time and labor, and the potential bulb yield increase into deciding whether to harvest scapes or not.
Peyton Ginakes, PhD
Research Associate
University of Maine Cooperative Extension
Highmoor Farm
52 US-202
Monmouth, ME 04259
(207) 933-2100
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.
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