For those of you I met at the OSU Extension Annual Conference in Corvallis (Dec 3-6 2018), it may be helpful to click here to learn more about the VegNet program, or feel free to contact me if you have questions.
Armyworms may be a problem in grass seed, pastures, fall-seeded brassicas, etc. this winter. Some species overwinter as larvae and can continue to feed if temperatures are mild enough. Check out the recent articles on our sister blog, Cutworm Central.
Continued and planned updates to the pest profile page, including Lygus bug…coming soon!
Some current hypotheses (from processors, OSU plant clinic, researchers, growers, field reps):
1. The damage may have been caused by heat stress during a critical time of development. In May and again in July, there were extreme variations of temperature:
Max daily temperature fluctuation in critical periods of seedling/transplant development likely contributed to poor growth observed this season
2. Auxins are phytohormones known to regulate growth processes in plants, and can spike rapidly in response to heat-shock. Increased auxin levels can ‘present’ as abnormal root growth or phototropism, which was noted at some of the sites:
As auxins move throughout the plant, the gradient shifts and, at least in other types of plants, declining levels causes leaves or petioles to break off. I don’t know much about abscission zones in broccoli, so if you are still reading, please know that these are just my rambling thoughts, and not an official diagnosis. 🙂
3. Another possibility is that young plants were sensitive to residual carryover from synthetic auxin herbicides (2,4-D, Dicamba, Fluroxypyr) remaining in the soil, which is possible with a grass-brassica rotation.
Recently, there has been some concern about odd symptoms of wilting and reduced stands in broccoli and cauliflower here in the Willamette Valley. See photos below.
Symptoms include: Weakened stems – necrosis of lower leaves – poor stand – girdling/calloused tissue at soil level – stem breakage – possible association with weed hosts – abnormal root growth
NOTE: AT THIS TIME, I HAVE ONLY EDUCATED GUESSES OF WHAT MIGHT BE CONTRIBUTING FACTORS TO THE FOLLOWING SYMPTOMS IN BRASSICA FIELDS. THIS ISSUE IS CURRENTLY UNDER INVESTIGATION IN CONJUNCTION WITH FIELD FACULTY AND DIAGNOSTIC LABS.
Cabbage rootfly (CRF-Delia radicum) is a well-known foe for brassica growers in this region. Normally, we do not expect them to be an issue mid-summer because
There are presumably two distinct peaks of CRF activity 1:
Spring – newly emergent adults; ~330 GDD = Mar 11th, 2018
CRF prefers cool weather and activity tends to diminish during the summer heat.
HOWEVER: Summer activity is measured by pan traps, and
Eggs were detected 4WAP and continued to be evident throughout the summer. There was a clear and steady increase in root damage starting at 3WAP in summer. Eggs were present in the fall as well, but the level of root injury was more gradual. (EGG count = top graph each season; ROOT damage rating = bottom) FROM: S.V. Joseph, J. Martinez / Crop Protection 62 (2014).
the authors of the model above agree that summer activity might have been underestimated because of ‘visible competition’ and attractiveness of blooming crops and weeds vs. yellow traps. The spring generation can be extended up to 3 weeks or more, depending on how long rainy, cool weather conditions persist. Also, we know that there are overlapping generations of CRF, and a study from California suggests that egg-laying behavior and subsequent damage during summer months is markedly different than fall:
ANOTHER FACTOR is that Delia radicum is actually part of a much larger ‘rootfly complex’, and different species have different ecological niches, behavior, and activity periods. This tableexplains some of those differences. Identifying rootflies is hard enough when they are adults, and nearly impossible as maggots and pupae. Thus, they are referred to as a pest complex that can affect growers year-round.
This puparium was found 27-Jul-18, suggesting that rootfly activity continues yearround in the PNW. It may be seedcorn maggot, radish maggot, or turnip maggot, as all are known to infest brassica roots.
1According to a regional model (Dreves 2006), and current 2018 data (Agrimet station CVRO)
Squash bugs have an elongated body shape and striped abdomen. Eggs are red and laid in clusters. Nymphs are gregarious, and progress in color from light gray to dark.
Anasa tristis is one of the squash bugs common in the PNW.
This pest is notoriously hard to detect, because they can hide on the underside of foliage, on plant stems, near irrigation lines, or even under fabric mulch.
Squash bugs use their piercing-sucking mouthparts to feed on leaf tissue and inject their saliva, which causes wilting of leaf tissue and, depending on the species, vectors cucurbit diseases.
Damage tends to be localized but can occur quickly because nymphs are gregarious, and feed alongside adults. If left undetected, vines eventually wilt and die.
Squash bugs have been a problem this year in the southeastern U.S., as noted by this news article.
[2018] According to a laboratory-based estimate, nymphal instars may be present in July, with a possible 2nd generation of adults in early August (model source: GDD58 single-sine, Fargo and Bonjour, 1988).
** 2019 Degree-Day Model Update**:
Adults noted East of the Cascades: June 27th (see report)
Eggs (predicted with GDD model, Corvallis): June 1st
Nymphs (predicted with GDD model for Corvallis): July 17th
Adult 2nd gen. (predicted with GDD model for Corvallis): Aug 4th
FOR MORE INFORMATION 1 H. B. Doughty, J. M. Wilson, P. B. Schultz, T. P. Kuhar, Squash Bug (Hemiptera: Coreidae): Biology and Management in Cucurbitaceous Crops, Journal of Integrated Pest Management, Volume 7, Issue 1, January 2016, 1, https://doi.org/10.1093/jipm/pmv024
Seed corn maggot – Poor emergence may be a sign of underground feeding by seedcorn maggots, which are the immature stage of Delia platura. Plants are most susceptible at seedling stage. Host plants include: corn, green and broad beans, onion, brassicas, peas, pepper, potato, spinach, and beet.
SCM is especially attracted to newly-tilled soil with high organic matter / manure inputs.
They have multiple, overlapping generations per year. This image by U. of Illinois highlights how adults, eggs, and maggots may all be present at the same time.
If emergence is low, scout 2-ft row sections for seed damage and white, tapered maggots that look very similar to cabbage maggot. Both species favor cool conditions for egg-laying, but D. platura are more active as adults in warm weather.
There is a fascinating biological (fungal) control for SCM that alters the fly’s behavior: It causes the flies to settle on tips of grain stems or high-up flowers and die, which increases dispersal of the fungus to spread farther.
Seed bugs– There have been recent complaints of high numbers of ‘small, flying insects’ in both urban and rural areas since mid-April. The bugs are 3-4mm with elongate bodies and wing covers with 4-5 veins. Experts agree that the taxonomy of this group is in need of a major revision, so they are usually referenced to genus level only.
More than half of all known Nysius species are from Hawaii, including the endemic wēkiu bug, that migrates to the summit of Mauna Kea each year.
Nysius spp. are seed predators and tend to be less selective then other, related Lygaeidae. Extensive damage can occur in wheat, quinoa, canola, and sorghum. Occasional feeding can occur on ornamentals, other cereals, and tomatoes.
Similar to boxelder bugs, they are attracted to large, sunny, white buildings, which has led to nuisance reports by homeowners. Various Ask-an-Expert questions have been submitted, one of which I was able to identify last week as Nysius, probably N. raphanus. The high numbers we are seeing now is likely the result of overwintered nymphs maturing into active, winged adults. There are 4-7 generations per year.
…the slimy worm-looking things covering the sidewalks around campus this week. They are the immature form of craneflies, commonly known as leatherjackets.
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I’m hoping it’s not too late to save our campus lawns, but by the time this kind of damage is apparent, insecticides may not be effective. By mid-May, the leatherjackets will pupate then hatch into adults. Adults are harmless (other than a nuisance).
Maintaining grass health is the best defense against craneflies. Monitoring should be done from January to March, when larvae are feeding underground. More information is available at: http://whatcom.wsu.edu/cranefly/Index.htm
NEW! OSU EXTENSION PUBLICATION (Sept. 2020): Managing Crane Fly in Lawns (EM9296)
Heavy infestation of leatherjackets (marker = approx. 2″)Grass can be pulled up like a carpet if severe cranefly damage has been done (CLICK FOR VIDEO).
Participating in the OSU Extension Open House last night was fun and rewarding (thanks, staff!!). I enjoy outreach events and inevitably learn something from interacting with the public.
Yesterday’s conversations led to today’s topic: “Problems with my PEAS”
In the span of two hours, three different citizens came to me wondering why their early-planted peas are being “attacked by an unidentified marauder” (direct quote).
All 3 inquiries were similar and there were some important clues present: leaves are being damaged from the edge inward (chewing mouthparts); not cut off at soil level (cutworm); nothing obvious when scouting at night.
WEEK 0: Spring has sprung and we need field sites. Broccoli plantings will be starting soon, cooperating growers are encouraged to contact me to reserve their spot. Cutworms and armyworms are likely going to be a problem this year.
Many have been spotted already, even on campus sidewalks (see below)! This species is especially fond of ryegrass and orchardgrass, and outbreaks have occurred in western Oregon.
So..why did the caterpillar cross the road? Because it overwinters as a partially mature larvae and peristaltic searching mobility increases when ambient temperatures exceed 10°C, of course!
**NOTE: this blog site will be used for extended story content, photos, etc. To access weekly pest reports and data (APR-SEPT), please subscribe to the email newsletter using the box at left**
In anticipation of this month’s release of Oregon’s Agricultural Progress research magazine, I wanted to put a brief post up to help orient OAP readers.
As you saw in the article, VegNet uses an email marketing platform to inform program subscribers about insect pesttrends throughout the Willamette Valley. Our readership includes vegetable growers, crop consultants, and home gardeners from across the country.
This program has been operational for 20+ years (!) and is truly a community resource.
The blog now has a ‘search by category‘ function located at left, if you are interested in a particular insect, or just want an easy way to browse through content. There is also an FAQ page. Or, you could go here to view all the reports from last year.
If this program interests you at all, please do join the mailing list to be included this season. Pest reports are delivered straight to your inbox, once a week, and only between April and October. The program is free, and you can unsubscribe at any time.
 
  
