WEEK 24 – Cabbage maggots are one of the most challenging pests for brassica growers. They tunnel through root tissue and increase the risk of exposure to plant pathogens Read this cabbage maggot page, which includes more info on biology and how to sample for them. Another late season pest is diamondback moth. Many sites are listed as "n/a" this week, because fields have been harvested and traps are being removed.
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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.
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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
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.
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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!!
WEEK 18 – Diamondback moths are exploding, and I try my hand at interactive maps!
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We monitor for cabbage loopers because they are pests of brassica crops. Feeding can occur on a wide variety of vegetable hosts including: beet, celery, cucumber, lettuce, pea, pepper, snap bean, spinach. Not all hosts are suitable for complete development of the insect, but feeding is feeding, from a grower or gardener’s perspective.
Plants, like insects, are ectotherms, which means that their rate of development depends on external conditions. Sure, most companies put ‘days-to-harvest’ on the seed packet, but we all know that is just an estimate, and can vary widely by region. It’s greatly influenced by temperature; especially if we encounter variations from the ‘normal’ levels of heat and/or rainfall.
Faculty at OSU Extension’s Small Farms Program and the Integrated Plant Protection Center have developed an online, predictive tool to help guide grower decisions and crop planning. The resource is called CROPTIME, and it provides models for a few of the crops grown in Oregon, with aims to develop 50 models (vegetables and weeds) eventually. Here is a 9-minute video that describes how to use the program.
This tool can greatly aid vegetable growers in estimating regional, temperature dependent phenology for a specific variety. For instance:
Broccoli Harvest Estimates - 2017
This information is collected from an online prediction tool, Croptime, from Oregon State University. The program is free to use and publicly available. Planting dates and varieties can be adjusted by the user and models are available for broccoli, sweet corn, cucumber, and sweet pepper.
*Estimates are accurate for W. Oregon only, these particular values are based off weather data near Keizer, OR.
50% head initiation
For more information, visit http://smallfarms.oregonstate.edu/croptime
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 16 – Two types of rootworm are now widely present in the Valley. See this page to learn how to ID and differentiate between them. Another, third species, may be on its way. Western corn rootworm has been moving westward since 2004.
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