Author Archives: greenje

Caution for Cucurbits

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This “CAUTION” post is similar to one I made a few weeks ago for cole crops; a quick way to highlight a potential problem, in hopes that consultants, gardeners, etc., will do some scouting to investigate if/to what extent they may be affected.

We saw, for the first time this season, some western striped cucumber beetle (Acalymma trivittatum) activity on both both weedy volunteer and cropped cucurbits.

This pest is of particular concern because it vectors bacterial wilt, a plant pathogen caused by Erwinia tracheiphila bacteria. Researchers now suspect that, rather than overwintering in the intestinal tract of adult beetles, the bacterium overwinters in the sap of alternate host plants (i.e. volunteer and weedy cucurbit species). The alternate host plants may not show symptoms of being infected, which can make management difficult.

As adult cucumber beetles feed, the beetles become infected with bacterial wilt, and then transmit it to crops. This infection can be direct (feeding on one host then another), or secondary (fecal contamination of already wounded tissue). Once the disease is established, it cannot be managed with pesticides, so ‘awareness’ of cucumber beetle activity levels, and subsequent control if necessary, is considered the best preventative tactic.

A few tips for scouting bacterial wilt in cucurbits:

    • Melons, squash, and cucumber are considered more susceptible than zucchini and watermelon, but all related plants (Cucurbitaceae) are at riska
    • Damage can occur quickly – scout 2-3X/week for beetle pressure and wilt symptoms
    • Symptoms can be immediate on some plants, and not occur until after fruiting on others
    • Leaves may look dull green, yellowing at leaf margins
    • Vines wilt during the day, but seem to recover at night
    • Quick diagnostic test (photos below): stems/vines are cut close to the crown, and a ‘stringy’ sticky substance appears when the two halves are pressed then pulled apart from each other. b
erwinia_knifecutting
1. make a clean, vertical cut close to the crown
2. push segments together then slowly pull apart

PHOTO CREDITS: Gerald Holmes, California Polytechnic State University at San Luis Obispo, Bugwood.org

 

 

There is a great new eXtension article about biology and management of cucumber beetles in organic farming systems available at: https://beav.es/ZYJ (it’s ok – we’ll use a Beavs shortlink to promote WSU just this once…there’s some great people/research going on up there!)

 

aDISCLAIMER: regional differences in pathogen expression are likely, do not rely on literature from other areas
bDISCLAIMER: may not work for all species or all cases

 

Week 7 update

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If you read this title and wondered “where are weeks 1 thru 6?” .. you need to subscribe! Weekly reports are sent directly by email, but sometimes there is so much happening, I have to do a mid-week update via blog. This is one of those weeks!

  • The cabbage looper outbreak continues, with trap counts averaging 1000 times higher than normal. Yes, you read that right.
  • 12-spot beetles. You see ’em, you know ’em, but did you know they can be devastating underground pests? The pictures below were taken this week on spinach for seed and seedling spinach (yes, there’s a difference).
    • As adults, beetles chew on foliage, flowers, fruit, corn silks, etc.
    • As larvae, grubs chew on and tunnel through roots.
    • For more info about 12-spots, click here; or branch out a bit and learn about the whole rootworm complex that plagues regional growers and gardeners.

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Caution for cole crop plantings

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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!

cone trap with about 60 visible looper moths inside
First indication of probable outbreak – May 8th 2019: too early to see this many

All the more reason to subscribe! Stay informed by clicking here. We do not share your information, and many of the pests we report on have wide host ranges, which means the data are relevant for home gardens, nurseries, and many commodity crops.

An example pest report can be seen here: https://mailchi.mp/f504f1497d5b/pest-report-week-4

Update: May 16th

Wireworms in W.OR?

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(Coleoptera: Elateridae) Agriotes spp.
Adults = click beetles; Larvae = wireworms

Spring is a critical time to assess wireworm populations because when soil temperatures warm to 50°F, larvae begin to migrate up within the soil column and seek underground plant tissues to feed on. Root crops are most commonly damaged, but chewing on seeds, seedlings, and fruit also have been reported.

I am coordinating a pitfall trapping effort to determine if non-native adult click beetle species are present in western Oregon (contact me if you’d like to participate). To monitor your own fields, bait stations are recommended, because they are a better indicator of actual, larval (wireworm) pressure.

I will post a more detailed pest profile page in the coming weeks, but for now:

For more information, click the link to read a publication by Nick Andrews et. al re: Biology and Nonchemical Mgmt. in PNW potatoes.

2-may-19 update: the PEST PROFILE PAGE is ready, and has more details about how to monitor, ID, etc.

Too Much Water

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…An uncommon phrase to hear in agriculture, but recent floods will have a dramatic effect and have already caused an estimated $12.5 billion dollar loss in the Midwest. Impacts include crop damage, inability to access fields to work ground or plant, and water contamination.

Here at home, the mainstem of the Willamette River and its tributaries (Long Tom, Mary’s, Callapooia) are in huge swells, with property flooding and road closures abundant. For current updates, check Benton and Linn County webpages or ODOT TripCheck.

High Water 02
A South Willamette Valley property was flooded Tuesday morning SOURCE: Andy Cripe, Mid-Valley Media / Corvallis Gazette-Times

From an insect pest point-of-view, the changes that may come about are uncertain, but I will be keeping a close ‘eye to the ground’. Flooding could cause mortality for some species (onion bulb mite, beetles, sawflies), promote growth in others (armyworms, mosquitoes), and have little effect on bugs that overwinter in sheltered areas (BMSB and ladybugs).

 

‘Twas a dreary day when I could finally get out to our research farm to assess damage to fields. However, our farm manager is resilient and those that have lived here longer say it’s “not that big of a deal”. I guess when you live in Oregon with 300 days of rain, you make your own mental sunshine.

Precision Ag Tools

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The definition of Precision Agriculture has evolved over 22 years and has more than a few associated acronyms (PA; SSCM=site-specific crop management; VRT=variable rate technology).

If one were to attempt to summarize the definition of PA: it involves awareness of growing conditions within a field and the use of technology as a decision support tool to maximize production efficiency while minimizing environmental impact of agricultural inputs.

We may be most familiar with PATs (Precision Agriculture Technologies) such as:

  • GPS-guided tractors or the use of
  • UAVs (unmanned aerial vehicles AKA “drones”) as imagery sensors or product applicators
  • Other PATs include robotic weeders and mechanized transplanters.
  • So many acronyms!

Check out The University of Sydney’s Australian Centre for Field Robotics promo video:

Resources closer to home include the UAS at OSU program, and a fellow Beaver blogger who has a great annotated resource list about Drones in Agriculture here. UAVs are even being used for restoration seeding efforts in Oregon rangelands.

Perhaps you’re not quite ready for autonomous tech. One simple and easy way to jump on the PA bandwagon is to use calibration tools. These are based on mathematical models of soil and crop parameters for a specific latitude, soil type, etc.. At the click of a button, they provide output estimates to help schedule irrigation, determine fertilizer needs, or predict harvest dates. These are in addition to the MANY mobile apps now available.

Another new trend (and a way to sneak in one last acronym) is for companies to offer SaaS: Software as Service, like our friends at Valley Agronomics.

As you go about planning and planting this year, why not give these PA tools a try. The program developers are usually very receptive to comments, as it helps them improve the models, or know that they are working adequately.

DISCLAIMER: Mention or links to any of the products or services on this page do not imply endorsement.
Computerized vision robot picker view of a mapping system to identify and target specific branches. credit: F. Moore
A grasshopper swarm detected by Nat’l Weather Service radar – Northern Montana, July 2021. View tweet

A word about IPM and MoA

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wordcloud of IPM terms
Aspects of Integrated Pest Management

Insecticides should not be the only plan of action when trying to control insect pests. But they are also an important and valuable tool. The National Roadmap for IPM supports chemical management as an option, but a main focus is to reduce the risk of resistance that may develop when a system relies too heavily on chemical management strategies.

Active ingredients in pesticides target different aspects of an organism’s growth. So, when implementing an insecticide use plan, it is very important to try to rotate chemistries, also known as modes of action (MoA).

Familiarize yourself with pesticide ‘group numbers’, and try to make choices that AVOID repeated use of the same product or MoA group. Otherwise, you may inadvertently be contributing to insecticide resistance, which means that sprays will be less effective, wasting your time and money. Group numbers are usually shown on a product’s label.

If you want to know more about this concept, may I suggest this video and other material available from the Int’l Resistance Action Committee (IRAC-online(dot)org). Other great resources include OSU’s Integrated Plant Protection Center (IPPC) and the National Pesticide Information Center (NPIC).

Mid-winter update

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A busy and wonderful few weeks!

  • 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!

 

What’s wrong with the broccoli? – UPDATE

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UPDATE 23-AUG

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.

Thanks for your interest/input.

 

Cabbage Maggot – a summertime problem?

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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
      • Fall – breeding flight; ~ 2400 GDD = Jul 14th, 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 table explains 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)