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!
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.
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. So many acronyms! Other PATs include robot weeders and mechanized transplanters.
Check out The University of Sydney’s Australian Centre for Field Robotics promo video:
Resources closer to home include the UAS at OSUprogram, 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.
WEEK 23 – Corn earworm flights have been consistently high, and scouting this week revealed late stage larvae, pupal exit holes, and newly-emerged adults that will lay eggs within 3-5 days. This diversity makes control difficult, and scouting is recommended. Spotted cucumber beetles do become active in the fall, but levels this year are about 500% higher than historical norms.
Read the full report here: http://bit.ly/VNweek23 and subscribe on our homepage to receive weekly newsletters during field season.
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
Western Corn Rootworm (WCR) is considered the most important corn pest in the U.S.1 . Most of this damage occurs in the Midwest, where corn acreage dominates the landscape. Over the last 50 years, farmers have used cultural, genetic, and chemical control strategies to lessen the effect of WCR and protect yields.
In comparison, the PNW produces a very small amount of corn (<5% of all regional farmland). Therefore, western corn rootworm has not been a problem for us so far2, and growers are much more accustomed to 12-spots (which is a western variant of the southern corn rootworm – confused yet?!)
Life histories are similar: larvae chew on roots, adult beetles attack foliage and can clip silk if populations are high enough. This interferes with pollination and can lead to poor tip fill.
Q: So why mention WCR if it’s not yet a problem here? A: This species is worth monitoring because it has been moving westward for the past 10+ years, and could become more abundant if corn production increases in the PNW. Yellow sticky traps are great passive sampling tools for many pests, so in short…might as well.
Gray, M. E., Sappington, T. W., Miller, N. J., Moeser, J., & Bohn, M. O. (2009). Adaptation and invasiveness of western corn rootworm: Intensifying research on a worsening pest. Annual Review of Entomology 54: 303-321.
Murphy, A., Rondon, S., Wohleb, C., and S. Hines. (2014). Western corn rootworm in eastern Oregon, Idaho, and eastern Washington. PNW Extension Publication 662. 7 pp.
WEEK 13: Early earworms; diamondback overlap – FULL REPORT HERE
Diamondback Moths are one of the smallest crop pest moths one is likely to encounter, but damage can be extensive. Part of the problem is their capacity to reproduce quickly, which leads to population buildup in a very short time. This is temperature-dependent and if not monitored, can catch growers off guard.
Corn Earworm is normally considered a late-season pest, but trends so far this year suggest a pattern similar to 2014, which resulted in a boom of moths in August, just as corn is silking. Larvae feed on corn silks and burrow into the ears. The resulting damage and frass (insect poop!) can cause delays in processing, or reduction of fresh-market value. This page shows how to identify corn earworm adult moths.
VegNet was featured in the July-Aug issue of OSU Linn & Benton Cty Extension’s Newsletter! Click photo to read the article.
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