VegNet Regional Pest Trends for the Week of May 11th, 2015

VegNet is an insect pest monitoring program funded by the Oregon Processed Vegetable Commission and managed by the Oregon State University Department of Horticulture. To add your name to this newsletter, please click the ‘subscribe’ button on the homepage.

Black Cutworm (Agrotis ipsilon)

If you are a “VegNet Veteran”, you may recall that black cutworm numbers were higher than normal in 2013 and 2014. At the end of last year, we cautioned that levels may be high again in 2015 due to a combination of overwintering pupa and migratory adults. To have the Valley average be at more than 2 moths per day this early in the season is alarming (FIG. 1). Although our BCW pheromone traps are placed at corn fields, this species has a wide host range and can injure cole crops as well as solanaceous vegetables (peppers, tomatoes, etc.). Adult moths are laying eggs now (even on our cone traps! (FIG. 2)), and larvae will develop over the next 20-30 days. As larvae progress, they become more damaging and less easy to control due to their subterranean feeding habits. Therefore, we recommend intensified field scouting over the coming few weeks. Foliar spray applications can be effective if they are applied soon enough. Consult the black cutworm pest page and the PNW Insect Management Handbook for more information about this pest.


FIG. 1 – Black cutworm moth trap counts are above normal for this time of year. FIG. 2 – Eggs are laid in clusters and hatch in 3-5 days.


Western Yellowstriped Armyworm (Spodoptera praefica G.)

Although not traditionally a pest that we monitor, appearances of this moth over the past 2 years have caught our attention. This species is native to Western states and according to some experts, populations are increasing in the PNW due to mild winters. The name of this insect refers to the broad yellow stripe visible on each side of the larvae. Adult moths have a characteristic wing pattern (FIG. 3), and there are 2+ overlapping generations per year. This species is a generalist feeder and skeletonizes leaf tissue. Population levels are usually kept in check by parasitoids and natural enemy predators. However, larval feeding can be significant on mint, beans, peas, potatoes, sugarbeets, and especially alfalfa, where it is considered a major pest. More information about this regional moth species can be found here.


FIG. 3 – Western yellow-striped armyworm has a distinctive pattern and can feed on a wide variety of host plants.

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