Over the past few days, I have seen 300+ cabbage looper moths in traps next to fields that aren’t even out of the ground yet, and been texted twice about flea beetle damage. It seems it will be a busy year for brassica pests!
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WEEK 18 – Diamondback moths are exploding, and I try my hand at interactive maps!
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We monitor for cabbage loopers because they are pests of brassica crops. Feeding can occur on a wide variety of vegetable hosts including: beet, celery, cucumber, lettuce, pea, pepper, snap bean, spinach. Not all hosts are suitable for complete development of the insect, but feeding is feeding, from a grower or gardener’s perspective.
Flea beetles invade fields rapidly, and can cause substantial damage to newly emerged leaves. Scouting is simple, thanks to the characteristic leaf damage. See photos and learn more here.
Rootworm is the common name for larval Diabrotica beetles. They feed underground, but can be distinguished from maggots by the presence of thoracic legs and a brown sclerotized plate just behind the head.
Cabbage Looper moths continue to be very abundant in the landscape. There is no diapause in this species, so 6-7 generations per year are possible if environmental conditions are suitable. Although trap counts are way above normal, the effect on crops has yet to be determined, and depends on a variety of factors. We will be discussing some of these in the weeks to come.
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* Continued pressure of cabbage loopers. An outbreak occurred in the Valley in 2008, when trap counts reached 100+ per day. Review last week’s post for details, interpretation of looper flights, and recommendations for scouting.
* A diamondback moth ‘point-concern’ for the Corvallis location. More data will be available in the coming weeks.
* True armyworms (M. unipuncta) are not traditionally monitored by VegNet, because damage is most notable in grasses and forage crops. However, feeding on peas, beans, and brassicas can occur in outbreak years. Visit the armyworm page for more info.
WEEK 5: First of two looper flights. Read the full report HERE.
The most notable trend this week is the sharp rise in looper activity. As seen in the graph below, 2016 levels (blue bars) were well above the historical norm (gray shaded line), and they remained that way throughout the season. This early 2017 peak (orange dot), while alarming, just means we’ll need to keep an eye on activity. It is the 2nd flight (Jul-Aug) that causes the most damage, because larvae and pupae contaminate crops headed for the processor. A contaminated crop can mean load rejection.
Home gardeners should be wary of looper levels, because larvae feed on a variety of crops including lettuce, tomatoes, peas, and other garden favorites. If you are concerned about defoliation, begin scouting between May 18th and 23rd. Look for ‘windowpanes’ or ragged holes, depending on how big the larvae are.
Processed vegetable growers are mostly concerned with looper flights near button-stage, as the main concern of this pest is contamination.
Looper larvae are light green with a white lateral stripe down each side, and display characteristic movement – ‘looping’ along the leaf surface by gathering the rear legs to meet the front legs and then extending forward. More info on loopers is available here.