Hi all,
As we enter the second week of May and fields begin filling with transplants and direct-seeded crops, several insect pests are emerging from their overwintering sites and searching for suitable host plants.
You can access our website via this link: https://go.uvm.edu/vpart. Also, in an attempt to improve communication with our team, we have added a couple of web forms on our webpage that will allow growers to directly submit any pest sightings or questions to our team. Direct emails from the VVBGA listserve are acceptable as well. As always, you can access our pest reports on our website or by directly navigating to the scouting blog.
Three of the most common maggots that we look for in the region are seedcorn maggot, onion maggot, and cabbage maggot. All of these pests emerge relatively early in comparison to other vegetable pests and are particularly troublesome as they can quickly damage young seedlings, roots, and developing stems before plants become established. Monitoring and early intervention are therefore critical during this early spring period for susceptible vegetable crops.
While direct scouting for eggs or adults can be difficult for these pests, as they can be quite small. A useful tool for monitoring and predicting the risk level for spring maggots is the Network for Environment and Weather Applications (NEWA) IPM tools website. This site allows you to track the emergence of important pests and diseases using their respective degree-day development models. The number of models available for vegetable production is somewhat limited, but many important fruit pests are included.
According to the current models, we should be seeing adult flies laying eggs in much of the Champlain Valley, as the overwintering generation is between 50% and 100% peak emergence. Cooler central and northern areas have likely not yet seen much emergence, but with warmer temperatures on the horizon, it is important to consider the potential risk. The most important time to protect crops is during the peak emergence of the overwintering generation, especially when plants are small and vulnerable. Growers can target larvae with insecticide-treated seed or an insecticide drench, or prevent damage altogether by keeping egg-laying female flies off plants with row covers. Row covers need to be in place before adult flies begin emerging.
Flea beetles are making their way into brassica crops here in Burlington and across the southern part of the state. Similar to root maggot flies, row covers for small seedlings can be an effective strategy for reducing their impact on the sensitive plants.
In addition to maggots and flea beetles, leek moth adults are also currently flying, as adult moths are being found in relatively high numbers on both sides of Lake Champlain in baited traps. Generally the emerging generation of leek moth seems to inflict less damage than the second generation typically flying in mid-June. This is the result of a combination of few available cultivated hosts and smaller overwintering populations. That said, if you have overwintered onions or other alliums in an area where you’ve had leek moth pressure in previous years it might be useful to take some action to protect smaller plants.
As a reminder you can access our website via this link: https://go.uvm.edu/vpart. Also, there are a couple of web forms on our webpage that allow growers to directly submit any pest sightings or questions to our team. Direct emails from the VVBGA listserv are acceptable as well. As always, you can access our pest reports on our website or by directly navigating to the scouting blog.
For detailed management information about these pests, as well as a comprehensive guide to current production and pest management techniques for commercial vegetable crops, check out the New England Vegetable Management Guide. And, as always feel free to reach out to us if you have any questions.
| Pest | Crop | Observations |
| Cabbage root maggot: | Brassicas | NEWA degree day models suggest that flies are currently laying eggs in the Champlain Valley and warmer areas |
| Leek Moth | Garlic | Adult flies are being trapped in western VT and eastern NY |
| Flea Beetle | Arugula, kale | Beetles are being found brassica crops. Row covers can be an effective strategy for protecting vulnerable brassica seedlings. |