{"id":179,"date":"2025-06-01T23:28:46","date_gmt":"2025-06-02T03:28:46","guid":{"rendered":"https:\/\/blog.uvm.edu\/vepart-scouting\/?p=179"},"modified":"2025-06-01T23:32:07","modified_gmt":"2025-06-02T03:32:07","slug":"vvbga-pest-and-scouting-report-6-1-25","status":"publish","type":"post","link":"https:\/\/blog.uvm.edu\/vepart-scouting\/2025\/06\/01\/vvbga-pest-and-scouting-report-6-1-25\/","title":{"rendered":"VVBGA Pest and Scouting Report (6\/1\/25)"},"content":{"rendered":"

Hi all,<\/span><\/p>\n

The rainy and cool weather continues to dominate throughout the region and has shaped pest populations here in Vermont. Many pests are persisting that, in previous years, may have waned in their damage, while others seem to be arriving later than usual.<\/span><\/p>\n

Some of the more persistent pests this season are the root maggots, particularly seed corn maggot<\/a>, cabbage root maggot<\/a>, and onion maggot<\/a>. These pests are currently being reported and\/or observed on various farms and seem to be causing significant damage. Seed corn maggot is the earliest to emerge in the season, while onion maggot is the latest (see degree day benchmarks below. According to degree-day models, onion maggot is currently at 50% peak emergence or less in Vermont. Fortunately, with the upcoming forecast of rising temperatures, we\u2019re hopeful we\u2019ll begin to transition out of this high-pressure period. Typically, warmer and drier soils reduce the viability of maggot eggs.<\/span><\/p>\n

\u00a0\u00a0 Degree-Day Thresholds for Maggot Pests<\/strong><\/span><\/p>\n

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Similar to the root maggots, slugs<\/a> and isopods (a.k.a. rollie pollies) are also thriving in these cool, wet conditions. These non-insect pests require very high humidity to survive\u2014which is nearly impossible to avoid right now. Sluggo is a highly effective organic option for slug control, and some growers report that it can help reduce isopod pressure as well.<\/span><\/p>\n

We\u2019ve received several questions about allium pests over the past week.<\/span><\/p>\n

Allium Leaf Miner (ALM):<\/a> This pest hasn\u2019t historically been a major issue in Vermont, as it typically emerges in late April and enters its \u201csummer hibernation\u201d by early June. Since the fly spends most of the summer (June\u2013September) in the soil as a pupa, it usually isn\u2019t a major concern for onion growers. However, it can affect scallions or leeks later in the season. A telltale sign of ALM is a line of small white dots on the foliage.<\/span><\/p>\n

Leek Moth<\/a>: As mentioned last week, the leek moth flight appears to be ending, meaning most of the population is likely in the egg stage on alliums. We\u2019ll be actively scouting garlic over the next couple of weeks for signs of caterpillar feeding and will report as soon as we see any. Typically, leek moth does not cause serious yield losses in onions or garlic, but it can be problematic if brought into storage on the foliage. Topping onions or garlic is a relatively effective, low-cost method to reduce their impact. Leeks, however, can be more significantly affected.<\/span><\/p>\n

Finally, with potato planting season underway for many farmers, we wanted to share some recent research findings on Colorado potato beetle<\/a>. In our delayed planting trials, we observed increased yields and reduced damage with plantings in late June to early July. The graph below shows results from a fully replicated trial at the UVM research farm. On-farm trials are currently underway, and we\u2019re always looking for volunteers\u2014or hearing from folks already trying some version of \u201cdelayed planting.\u201d<\/span><\/p>\n

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Be on the lookout of the following pests:<\/span><\/p>\n

Some pests that are being reported in more southernly and warmer regions are:<\/span><\/p>\n