You’ll notice that we emphasize the importance of ‘scouting’ on this blog a lot, but what is one supposed to do when they find something? Lots of immature bugs can be found in the soil and it can be difficult to distinguish a “baby” beetle from a fly from a caterpillar, etc. This post might help…
Continue readingCategory Archives: pest ID
Sap Beetles in Corn
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 Carpophilus lugubris, 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.
Seed Maggot Problems
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.
Learn More About Seedcorn Maggot:
- PNW Handbook Sections
- Related blog post (Jan 25, 2021) – aka all about maggots on one page with link to a video by Dr. Nault, a SCM expert
- Related blog post (May 18th, 2018)
- 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.
Leafrollers & Leaftiers
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…
Continue readingThey’re boxelder bugs
We have received many emails this week about ‘home invasions’ of odd-looking bugs. In each case, the culprits were boxelder bugs. Although easily recognized as adults, the partially mature phase (nymphs) can be unfamiliar.
Nymphs and adults aggregate in large groups, especially on light-colored homes with a warm-facing side. The concern for damage on ornamental or fruit trees is low. Rather, these are considered a nuisance pest. The sheer and sudden numbers of them is what causes calls to come in.
FOR MORE INFO:
https://pnwhandbooks.org/node/6798/print
http://ipm.ucanr.edu/PMG/PESTNOTES/pn74114.html
Week 7 update
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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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.
Pest Report – Week 7
WEEK 7 –
- 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.
- 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.
They’re Leatherjackets
…the slimy worm-looking things covering the sidewalks around campus this week. They are the immature form of craneflies, commonly known as leatherjackets.
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)
Early Pea Problems
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.
The probable pest producing pack perturbation
IS ….
Pea Leaf Weevil !
(More info available in the pest profile section)
