{"id":13324,"date":"2026-06-04T15:12:41","date_gmt":"2026-06-04T19:12:41","guid":{"rendered":"https:\/\/extension.umaine.edu\/highmoor\/?p=13324"},"modified":"2026-06-04T15:12:41","modified_gmt":"2026-06-04T19:12:41","slug":"garlic-ipm-newsletter-no-6-june-4-2026","status":"publish","type":"post","link":"https:\/\/extension.umaine.edu\/highmoor\/2026\/06\/04\/garlic-ipm-newsletter-no-6-june-4-2026\/","title":{"rendered":"Garlic IPM Newsletter No. 6 — June 4, 2026"},"content":{"rendered":"
\"Close<\/a>
Necrotic garlic leaf tip with dark spores typical of purple blotch or Stemphylium<\/em> leaf blight. Photo by June Foyt, UMaine Extension.<\/figcaption><\/figure>\n

Much of Maine has enjoyed a nice stretch of warm and dry weather heading into the weekend. Garlic is developing nicely at all scouting locations. The NEWA onion disease forecast<\/a> remains clear for Maine locations through June 9, but keep in mind that this updates with the weather forecasts, which have been erratic. Check these forecasts regularly<\/strong> if you are using them to time scouting efforts (as for Botrytis<\/em> leaf blight and Alternaria<\/em> purple blotch) or initial prophylactic controls (as for onion downy mildew), after which a 7-10 day spray schedule should be maintained. Rotate FRAC codes with every application to manage resistance. The New England Vegetable Management Guide<\/a> offers a good starting list of controls, and this Cornell “cheat sheet” displays efficacy results from their latest fungicide trials in onion<\/a>. Cultural management options focus on minimizing leaf wetness by controlling weeds, so as to improve airflow in the crop, and refraining from overhead watering.<\/p>\n

Botrytis<\/em> leaf blight lesions have levelled off in all but one scouting location (Washington). However, leaf tips are beginning to take on a “dirty” appearance at all scouting locations to varying degrees, which is typically the result of Alternaria<\/em> purple blotch (PB) or Stemphylium<\/em> leaf blight (SLB) sporulation. These pathogens are fairly ubiquitous in allium plantings, and readily colonize the weak or dying tissues of leaves as they die back. This may not represent a major economic risk to garlic crops. Still, controls in garlic may be warranted if other alliums are nearby, since severe foliar infection in onions can reduce yield and prevent proper lodging, resulting in bulb rots.<\/p>\n

Onion Thrips Update<\/h3>\n

Low numbers of onion thrips have been found in Monmouth, as expected based on the growing degree day model. Sufficient GDDs have accumulated for thrips to emerge in southern Maine, from Kittery north to Newry, Farmington, Augusta, and Damariscotta. Next week’s newsletter will discuss onion thrips biology, crop damage, and management in more detail.<\/p>\n

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Onion Thrips GDDs through June 3, 2026<\/strong><\/h4>\n<\/caption>\n

Location<\/th>\nOnion Thrips
\n140 GDD52.7F<\/sub><\/th>\n<\/tr>\n
Augusta<\/th>\n154*<\/td>\n<\/tr>\n
Bangor<\/th>\n128<\/td>\n<\/tr>\n
Calais<\/th>\n88<\/td>\n<\/tr>\n
Caribou<\/th>\n63<\/td>\n<\/tr>\n
Cherryfield<\/th>\n99<\/td>\n<\/tr>\n
Clayton Lake<\/th>\n64<\/td>\n<\/tr>\n
Cutler<\/th>\n16<\/td>\n<\/tr>\n
Damariscotta<\/th>\n153*<\/td>\n<\/tr>\n
Dover-Foxcroft<\/th>\n123<\/td>\n<\/tr>\n
Ellsworth<\/th>\n114<\/td>\n<\/tr>\n
Embden<\/th>\n137<\/td>\n<\/tr>\n
Farmington<\/th>\n151*<\/td>\n<\/tr>\n
Fort Kent<\/th>\n57<\/td>\n<\/tr>\n
Fryeburg<\/th>\n185*<\/td>\n<\/tr>\n
Greenville<\/th>\n75<\/td>\n<\/tr>\n
Katahdin<\/th>\n10<\/td>\n<\/tr>\n
Kittery<\/th>\n205*<\/td>\n<\/tr>\n
Lewiston<\/th>\n164*<\/td>\n<\/tr>\n
Lincoln<\/th>\n110<\/td>\n<\/tr>\n
Houlton<\/th>\n83<\/td>\n<\/tr>\n
Jackman<\/th>\n80<\/td>\n<\/tr>\n
Millinocket<\/th>\n105<\/td>\n<\/tr>\n
Newry<\/th>\n163*<\/td>\n<\/tr>\n
Northfield<\/th>\n91<\/td>\n<\/tr>\n
Portland<\/th>\n152*<\/td>\n<\/tr>\n
Sanford<\/th>\n205*<\/td>\n<\/tr>\n
Rangeley<\/th>\n79<\/td>\n<\/tr>\n
Thorndike<\/th>\n124<\/td>\n<\/tr>\n
Topsfield<\/th>\n85<\/td>\n<\/tr>\n
West Rockport<\/th>\n127<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/div>\n

The table lists GDDs from Maine Climate Office website<\/a> and numbers marked with an asterisk (*) indicate that sufficient GDDs have been met in that location for onion thrips to emerge, and regular scouting is warranted.<\/p>\n

Now is the time to look out for leek moth<\/h3>\n

We are continuing to monitor for leek moth around the state and have yet to find any signs of this invasive pest. However, since leek moth has already been reported in New Hampshire this year, it is advisable to keep an eye out for it, especially in western Maine. Adult moths emerge in spring when temperatures reach 50\u00b0F and lay very small eggs on allium leaves – often garlic, since it is one of few alliums in the field at this time. When larvae hatch, they feed on and mine through leaves and sometimes scapes; this feeding damage is often the first sign of this pest since the moths are nocturnal. In onions and other alliums with hollow leaves, feeding from inside the leaves creates a “windowpane” effect since larvae do not eat the outermost layer. Larvae continue to feed for about 2-3 weeks before pupating in cocoons that look like cargo nets.<\/p>\n

Larvae<\/h4>\n