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
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
* Link to ID guide (Savage et al. 2016) but beware, it involves counting and measuring hairs on adult fly thoraces and legs – good times!
When people talk about beetle pests in corn, they’re usually referring to damage that occurs below the soil level. For many species, including western corn rootworm, wireworms, and white grubs, the common name refers to the immature stage that attacks corn roots underground.
So, when i saw this beetle-looking-larvae feeding ON developing kernels this week, I was intrigued and confused. And “well, maybe I was a little bit… ‘concerned'” [obscure movie quote, congrats if you know it ;)]
Coleoptera: Nitidulidae are small, oval to elongate beetles with clubbed antennae and shortened elytra (wing covers). Feeding habits vary, but adults tend to feed on fresh or decaying organic matter. Because of this, they are often called fungus or pollen beetles (e.g. Meligethes aeneus in brassica, canola, and clover production). Aethina tumida, the small hive beetle, is another example.
The specimen I found near Scio is probably Carpophiluslugubris, a N. American native and known pest of sweet corn.
Can be a problem in both processed and market corn, because larvae feed within the ear and damage is not always visible until after husking.
Beetles are most attracted to ears damaged by rodents, birds, deer, etc. or when harvest operations leave lower ears – can become a reservoir.
May have correlation with volatiles expressed by the plant after attack by corn earworm
Common in stored grains and nuts; feces can contaminate dried fruits
Larvae develop for ~ 3 weeks then pupate in the soil, adults can live up to 300 days, 1 generation/year
NOTE: Dusky sap beetles can also cause damage in TOMATOES, STRAWBERRIES, and other soft fruits – just don’t have time to elaborate on that today!
UPDATE: sap beetle found in large numbers contributing to onion rot – OCT 2020. Access the scouting report.
Growers and field reps throughout the region have been noticing issues with seed maggots. Similar to root maggots, these are the immature form of a certain type of fly (Diptera: Anthomyiidae: Delia spp.).
There are three species, in particular, that can be devastating in vegetable crops. The first, cabbage maggot (D. radicum) is well-known and tends to infest brassicas only. Use this link for more info on cabbage maggot.
“Seedcorn maggot” is the common name for what is actually a complex of two species – D. platura and D. florilega. “Bean seed fly” is another commonly used name for adults. These two species are remarkably similar, both as larvae and adults. For adult flies, color is variable and one must examine leg hair length and placement. Maggots are indistinguishable, even by experts.
Complaints so far have come from parsnip and snap bean fields, but dry beans, corn, peas, and squash growers should take note. If emergence is low, scout 2-ft row sections. Look for damage to seeds and white, tapered maggots. Maggots are legless and have a blunt posterior.
PHOTOS ABOVE ADAPTED FROM: Savage, J., Fortier, A-M., Fournier, F., Bellavance, V. 2016. Identification of Delia pest species (Diptera: Anthomyiidae) in cultivated crucifers and other vegetable crops in Canada. Canadian Journal of Arthropod Identification No. 29: June 29, 2016. doi:10.3752/cjai.2016.29
Brooks, A. R. 1951. Identification of the Root Maggots (Diptera: Anthomyiidae) Attacking Cruciferous Garden Crops in Canada, with Notes on Biology and Control. Can. Entomol. 83(5): 109-120.
Higley, L. G. and L. P. Pedigo. 1984. Seedcorn Maggot (Diptera: Anthomyiidae) Population Biology and Aestivation in Central Iowa. Environmental Entomology. 13(5):1436-1442.
Larvae of various Tortricid moths (Lepidoptera: Tortricidae) are well-known pests to fruit and nut growers, but less considered in vegetables. Here is a quick list of some economically important species in this group:
Light Brown Apple Moth (Epiphyas postvittana)
Fruittree Leafroller (Archips argyrospila)
Codling Moth (Cydia pomonella)
Filbertworm Moth (Cydia latiferreana)
Strawberry Fruit Worm aka Omnivorous Leaftier (Cnephasia longana)
These small, bland colored moths are nearly undetectable in the landscape, but their larvae can cause billions of dollars of economic damage. Leaves are rolled or tied to provide shelter for developing larvae. Crop damage from this group can occur ‘from root to fruit’. Read more and see photos below…
Another attention-grabber headline this month is the hatch of periodical cicadas in the eastern US. “Brood IX” is a 17-year assemblage that was expected, but there are “stragglers” from other groups of 13-year cicadas that are actually 4 years early. This year is unusual because the groups consist of many different species (all in genus Magicicada) and appear to be overlapping geographically. Confused yet? Me too, so I refer you to http://magicicada.org/magicicada/ if you’re interested.
Sounds are produced by specialized structures called tymbals, and can exceed 100 decibels! If you’ve never been lucky(?) enough to hear one, enjoy this video clip:
Cicadas are not ‘locusts’ ( which are a behavioral adaptation of grasshoppers). They’re more closely related to leafhoppers and spittlebugs.
Common cicadas have life cycles between 3 and 5 years. Nymphs (immatures) live underground and feed on tree roots.
If you see a green cicada, it is not a periodical species.
Emergence in the PNW may be related to rainfall: Chatfield-Taylor, W. and Cole, J.A. 2017. Living rain gauges: cumulative precipitation explains the emergence schedules of California protoperiodical cicadas. Ecology 98: 2521-2527.
We do, in fact, have cicadas in Oregon, but they do not occur at nuisance levels. There are ~ 30 species in our region; one of the most encountered is Okanagana oregona (pictured at right).
News & Updates re: Brood X
ARTICLE A great summary by the Entomological Society of America re: Brood X impact, coverage by media, tracking apps, interviews with leading experts, and even a music video! Aug 12, 2021, ESA
VIDEO (00:02:30) Great quality footage and overview, and a University of MD. Emeritus professor describing them as ‘delightful‘. SOURCE: May 17 2021, Reuters
One of my favorite other ‘hats’ is being an Entomology educator for K-5 and guest speaker for Education students who are doing their teaching practica. I was serving in this role last week, and thought I should mention cicadas to the kids, just in case. The morning after our Zoom visit, the teacher sent this picture of a newly eclosed cicada they spotted on a tree. Great catch, Little Wolverines, and I’m so proud of you for being observant!!
There are many black and yellow wasps in Oregon. Proper identification is important before reporting. Here are some ID tips:
This wasp is very LARGE! 1.5″ to 2″ long
It has a striped abdomen, yellow head, and black eyes
The thorax (where wings attach) is black
Predator of many large-bodied insects (grasshoppers, beetles, etc.)
Potential serious threat to honeybees
Ground-nesting, active from May to August
Detected in August 2019 British Columbia (eradicated); 0 confirmed sightings to date in Oregon. 4 confirmed sightings (dead) in Washington state + 1 active nest – read news articles from October 2020;
OTHER REGIONAL RESOURCES
There are a number of regional experts who can offer advice, answer questions, and field suspected reports of sightings. Please consult the OSU Extension publication for ID tips, answers to common questions, etc. Early detection is key to limit the effects of invasive species.
Ask-an-Expert – Featured question from homeowner, answered by OSU faculty (AUG 2022)
This is a summary of an article published in the Winter 2020 issue of the Oregon Small Farm News. The article was written by Dr. Toshihiko Nishio and translated and edited by Shinji Kawai and Abigail Hunter, OSU Dept. of Horticulture. The article is available as a .pdf by using the link below.
In 1967, an ocean vessel was in the East China Sea conducting standard atmospheric and marine environment monitoring when, all of a sudden…
Little did the ship’s crew know – that experience would help scientists learn more about a very serious pest problem in rice. In fact, rapid invasions of planthoppers is thought to be one of the major causes of historical famines in Japan.
Ryoichi Kishimoto, who worked at a local agricultural research station formed a group to intensively study the planthoppers. They set up light traps, pan traps, and even windsocks to monitor at different locations throughout the region. In 1971, Kishimoto published his theory about long-range migratory patterns of the pest, which ignited international interest.
20 years after the original observation, another researcher from the same experiment station proved that the planthopper’s migration corridor includes a low-level jetstream from southern China to western Japan. This is how they are able to travel such massive distances in just a few days, and why they would’ve been observed by the ocean vessel.
Some growers tend to think of birds as chronic annoyances. Solutions range from preventative tactics (netting and birddogs) to scare tactics such as artificial predator calls and driving around the farm firing empty shells at murders – sound familiar?
But a new study suggests that certain birds can – and should – be welcomed as a part of an overall sustainable farming strategy. The link below explains:
The email that went out to subscribers Monday clarified that yes, we are done monitoring and reporting for the 2019 season. You can read that message here.
But please do continue to visit this blog for these and other updates:
Summarizing 2019 pest trends
A comprehensive written report will be available at the vegetable grower’s meeting and OPVC website by Jan 2020.
Investigating why corn earworm was so minimal in W. Oregon but very abundant E. of the Cascades and also in the midwest.
Cabbage looper outbreak: if it affected load rejections; possible prediction of outbreaks; how new methods of counting became necessary due to 1200+ moths per trap (see photo below)
Continued armyworm trapping
Cooperators in Tillamook county will continue to operate pheromone traps and scout fields through October because fall activity is common.
Trap counts are updated each week http:// beav.es/ZY3 and we are in the process of mapping them to examine if any geographical patterns are evident.
23 years of a darn-solid phenology dataset is nothing to scoff at. I have spoken with some of you about collaborating on a journal article. Dan would be proud, and I…well..need to. Maybe we’ll have enough rainy days this winter to actually accomplish it. Contact me if you’re interested.