A new study from WSU indicates that peas respond to herbivore damage differently depending on if they are attacked by pea weevil or pea aphid first. Transmission of the pea enation mosaic virus (PEMV) is also affected. These biologically relevant interactions have implications for management. A very interesting study, well done, Cougs! https://news.wsu.edu/2021/08/10/pest-attack-order-changes-plant-defenses/

The natural enemy of my enemy is my friend! We start seeing increased activity of beneficial insects this time of year. Everyone can identify a ladybug, a select few know what a lacewing looks like, but did you know that certain flies, beetles, and even yellowjackets also help to regulate pest populations?

CLICK TO VIEW a newly revised OSU Extension publication about natural enemies

READ RELATED POSTS here on the blog

and GO OUT and look on crops, wildflowers, and weeds (especially wild carrot right now) to see these “good guys” in action!

Doesn’t seem possible but we are in week 7 of the 2021 monitoring season. It has been a slow and rather uneventful start, compared to recent years, but predictions of extreme summer heat and drought could change that.

  • Data tables are available for week 6 and week 7
  • Looper levels remain VERY low
  • An early (Apr-May) boom of cabbage white butterfly means greenworms could be present in gardens and fields – scout accordingly
  • Aphid scouting will once again be part of VegNet’s regional monitoring effort. See the aphid profile page for more info
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Three years ago, my field season was so affected by yellowjackets (FIG. 1) that I decided to find out what I could learn about them. Their abundance, activity, what influences populations, etc. It was actually harder than I thought to find information! This was noted by a 2018 paper , where the team investigated 908 published papers over almost 40 years and yep – less than 3% of them were wasp-related (FIG. 2).

Despite the importance of both taxa, bees are universally loved whilst wasps are universally despised.”

Seirian Sumner et al., 2018
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While none of us have a crystal ball, especially in agriculture, I thought it might be fun to offer some thoughts / warnings of how this year might look for insect pests of vegetables. I predict* ……

  • “Flea beetles will be rampant.” In the spring, adult flea beetles emerge from overwintering, and are already causing some problems in radish. We’ve been told by both local and regional sources that it’s going to be a hot and dry summer = flea beetles’ favorite weather. I suggest early and often scouting in brassica crops. Starting now, begin to scout weedy areas around fields. Once the crop emerges, or shortly after transplanting, focus efforts on field edges. It may be necessary to scout daily – yes, daily. Be aware that these insects are easily disturbed (they jump), sticky traps placed ~10″ off the ground can help assess activity – place them near edges. You’ll recognize the distinctive ‘pitting’ on cotyledons and true leaves. Check stems for signs of damage as well, just above the soil surface. For more information, see the flea beetle pest profile page.

  • “Wireworms are a cryptic foe we should get to know.” They are a common problem in grass and potato production. Adult click beetles do not live for very long and do not cause damage. Larvae (wireworms), on the other hand, live for 2-6 years and damage can be extensive. Before planting, especially if you are coming out of a grass rotation, take my advice and place a few bait traps to assess larval activity. Instructions and more information is available at the wireworm pest profile page.

  • “Every other year, cabbage loopers cause fear.” Ok, I admit, this one is just a stretch to fit the rhyme scheme. However, it is true that in the Willamette Valley, we have had major looper outbreaks in 2017 and 2019… so 2021 is a possibility. Trap count data will be available soon.

* PLEASE NOTE: these are merely educated guesses. In fact, part of the fun of monitoring insects is that they are truly so unpredictable!

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I mentioned in last week’s newsletter that the Oregon Dept of Agriculture (ODA), Washington State Dept of Agriculture (WSDA), and Washington State University (WSU) are all active in their efforts to prevent and detect Japanese beetles in the region. Remember:

  • This Thursday, April 1st, at 9am, WSU/WSDA is offering a webinar. Click here to register and learn more.

Also be sure to check out the OSU Extension publication that includes information on identification, life cycle and scouting, damage, control measures, and how to report a suspected Japanese beetle. EM 9158    Published April 2017 4 pages https://catalog.extension.oregonstate.edu/em9158

Please help us get valuable information about chlorpyrifos 

  • Restrictions on the use of chlorpyrifos and the complete revocation of its registration are underway.
  • An ODA specialty crop block-funded project involves a cross-commodity collaboration to identify viable options as alternatives to chlorpyrifos.
  • The research will be conducted at several locations in Oregon to determine the efficacy of currently registered chemistries and newer products in onion, corn, cherries, grass seed, and clover seed.

Your responses to this survey help us identify critical issues that can improve the development of our research. Please participate in this 10-minute survey and enter for a chance to win one of ten $25 gift cards. 

If you have questions or comments about the project, please contact Silvia Rondon, Project Leader, OSU Hermiston Agricultural Research and Extension Center, 541-567-8321, silvia.rondon(AT)oregonstate(DOT)edu. Sent on behalf of Silvia Rondon, Dani Lightle, Navneet Kaur, Chris Adams, and Stuart Reitz.

Please use the link below to participate.

Thanks in advance for your time and feedback!

https://beav.es/JaP

After this morning’s invited speaker talk (OPVC Annual Grower Meeting), I thought it might be helpful to assemble some existing resources we have about Delia spp. in the PNW. Browsing these links could help you better prepare for the planting season. Also feel free to leave a comment with any specific concerns or impact you’ve experienced. Thanks to Dr. Nault for a great presentation this morning!

  • ** VegNet alert – late June 2020 – Seedcorn maggot issues reported/confirmed in snap bean and parsnip
  • ** Pest profile page – Seedcorn maggot species complex, literature
  • ** Pest profile page – Cabbage maggot overview, ID, management
  • Temporal trends – late July 2018 – Temporal trends and species complex info
  • Scouting report – mid Oct 2020 – Maggot complex found in stored onion
  • Research report (pdf) – 2016 maggot trial in direct-seeded radish, chlorpyrifos alternatives
  • VegNet alert – May 2018 – Poor emergence, general info seedcorn maggot
  • U. of Mass. factsheet – Seedcorn maggot
  • Dr. Brian Nault, lab site – Cornell Entomology (pdf) – Delayed planting to help manage onion maggot

Root maggots are creamy white to yellow, opaque, and legless. They are tapered; blunt posterior end. Determining species is difficult and requires examination with a microscope.

Root Maggots of the PNW – Overview

Delia species (Diptera: Anthomyiidae). Small (5-8mm) flies – black, brown or grey – the immature phase are called maggots – they feed on root and sometimes stem tissue – identification technical and difficult* – often referred to as a rootfly ‘complex’. Adults do not cause damage. Eggs are laid at the base of plants. Maggots tunnel into tissue which causes direct damage and also increases the risk of infection by plant pathogens..
D. radicum: Cabbage maggot
Our most familiar regional issue. Adults prefer cool weather and maturing (4-7 leaf) brassica plants to lay eggs. Flight period well-documented and can be useful for predicting timing of egg-laying pressure.
HOSTS: weedy mustards, broccoli, cauliflower, etc.
.
D. platura: Seedcorn maggot
Attracted to organic matter and decay. Sometimes worse in fields that have been cover cropped to increase N. Often a secondary pest (invades after initial decay of tissue due to other factors). Active earlier than other species.
HOSTS: many, but especially large seeded vegetables like corn, peas, dry beans, snap beans
.
D. florilega: Bean seed maggot
Nearly indistinguishable from D. platura, often occur together.
HOSTS: association is broad, but mostly a problem in turnips, radish, canola
.
D. planipalpis: Western radish maggot
Similar in appearance to D. radicum, but different leg hair arrangement.
HOSTS: radish and canola (verified in literature); also probably other crucifers
D. antigua: Onion maggot
A major problem in onion production. Many good resources available.
HOSTS: onions, garlic, chives, etc.
.
D. floralis: Turnip maggot
Similar in appearance to other species; different leg hair arrangement.
HOSTS: turnip and radish
* Link to ID guide (Savage et al. 2016) but beware, it involves counting and measuring hairs on adult fly thoraces and legs – good times!