Pleased to announce I was invited to participate in a nationwide analysis of corn earworm trends. This new study from Dr. Lawton (NC State) et al. takes a look at decades-long trapping and soil temperature data to provide some insight into overwintering potential of H. zea, and how we might use models to predict pest abundance. Highlights from the article:Continue reading
Category Archives: degree-days
A Slow Start!
Unseasonably cool and wet conditions have delayed the start of VegNet this year. Because insects are poikilotherms, their development is directly related to temperature. Some insects are also reliant on adequate moisture. The percentage of armyworm eggs that hatch, for example. We certainly have had ‘adequate’ moisture this spring (!), which could mean more armyworm pressure into the summer and fall.
Maggots: gross impact of a gross group
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 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
Wireworms in W.OR?
(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.
Precision Ag Tools
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.
- Oregon State University Croptime (web app) and Jan 2021 publication re: using it for “Vegetable Degree-Day Models“
- Louisiana State Univ. Spreader calibration (.xls)
- Univ. of Florida Irrigation scheduler (.xls)
- WSU’s project on robotic arm harvesters for apple orchards. PI: Dr. Manoj Karkee (online news)
- “Driverless Farm Machinery May Lead to New Business Model” – Capital Press article, Jan 22 2020 (online news)
- TerraSentia robots deployed to collect seed and canopy data – AgProfessional news, July 9 2020
- “Prospects for Remotely Piloted Aircraft Sytems (RPAs) in IPM” discusses the opportunities, current technical and legal constraints, and applications such as: targeted insecticide applications, and aerial releases of sterile insects and parasitoids (book chapter) 2020
- WSU researchers using drones and enhanced satellite imagery for riparian scouting “Eyes in the sky”, Feb 2021
- MDPI’s “Agriculture” journal is open access, and has over 300 articles about Digital Agriculture. Papers include research on imagery and detection systems, using neural networks to predict seed yield, all kinds of cool stuff!
Cabbage Maggot – a summertime problem?
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.
- There are presumably two distinct peaks of CRF activity 1:
HOWEVER: Summer activity is measured by pan traps, and
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.
1According to a regional model (Dreves 2006), and current 2018 data (Agrimet station CVRO)
Squash Bug season
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.
** 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
2 PNW Insect Management Handbook section
3 This page shows how to differentiate squash bug, BMSB, and others
BMSB in Veg Crops
Tis’ the Season! According to a pest model for this region, the summer generation of brown marmorated stink bug (BMSB) adults start appearing this week. This pest is very mobile, and will move into fall crops readily. I caught a glimpse of an egg mass in sweet corn today (photo below), and nymphs are expected to peak within the next few days.
Bell pepper, sweet corn, and tomato are all considered desirable hosts. Symptoms include sunken kernels, whitening on fruits, and spongy tissue. Rather than re-invent the wheel, I decided to direct you to some GREAT resources (see list below) for BMSB ID and management in vegetables.
FOR MORE INFO:
Wiman lab page – Oregon State University – Identification, monitoring efforts, and resource list
Neilsen et al., 2008 – Rutgers University – Developmental details
BMSB info for vegetable growers – great photos of injury, explanation of life cycle, etc.
Pest Report – Week of August 21st
WEEK 20 – Diamondbacks continue to hatch; corn earworm flight; beneficial insect tracking. Perhaps most importantly: we found 5 Large Yellow Underwing Moths (the adult phase of winter cutworm)in traps this week. More information is available here.
Read the full report here: http://bit.ly/VNweek20 and subscribe on our homepage to receive weekly newsletters during field season. Thanks!
Rise of the Predators
SURVEY QUESTION: What’s this bug?
ANSWER: A lady beetle pupa, which is the life stage between larva and adult. Ladybug pupae affix themselves to a leaf surface to complete development. Do not try to control them – these are good guys!
All this talk about crop PEST insects should not go unaccompanied by at least a brief mention and applaud for those silent heroes, the BENEFICIALS!
Biological control by generalist predators can be quite effective at mitigating pest insect populations, depending on the circumstance.
Two of the most common predators that we see in vegetable crops are ladybird beetles (ladybugs) and lacewings. I decided to track activity of these two groups this year, just to see if any activity patterns would be evident.
Ladybugs and lacewings can be passively sampled with yellow sticky traps. Although, for a more detailed study, one would want to incorporate sweep net sampling, increase trap numbers per acre, etc.
The convergent lady beetle (Hippodamia convergens) is a native species. They overwinter as adults, mate, and then lay eggs in the spring. A study from Corvallis using field-collected H. convergens found that 228 growing degree-days (above a threshold) are required for development from egg to adult, and that this heat-unit requirement is rather consistent throughout North American populations (Miller 1992 Env. Ent. 21).
These graphs show a clear pattern of increased ladybug activity (adults on sticky cards) beginning around late June-early July. Sure enough, the increase correlates with published heat-unit requirements, and is confirmed by a degree-day model and online phenology tool (uspest.org, check it out!)
Cool! But what does all this mean? Well, it suggests that passive sampling is a good way to estimate ladybug phenology, and could provide us with comparative data on predator activity differences between years.
Perhaps more importantly: recognize that while it takes ~230GDD to detect ADULT ladybugs, the larvae are predacious too and have been busy in your fields and gardens all spring!!