WEEK 23 –
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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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.

poor tipfill of corn
Poor pollination during silking affects tip fill. This picture is from the Midwest, where WCR is a much bigger issue than it is in the PNW. PHOTO CREDIT: J. Obermeyer

 

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.

Expansion of WCR in 10 years. Based on C.Edwards and J. Kiss (Purdue Field Crops IPM) and A. Murphy (OSU, PNW 662)

RESOURCES:

  1. 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.
  2. 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.

Read the full report here: http://bit.ly/VNweek16 and subscribe on our homepage to receive weekly newsletters during field season. Thanks!

WEEK 15 full report available here:

  • Black cutworms will be large now, and can cause major root damage in corn. Consult the PNW insect management handbook for possible rescue treatments.
  • Diamondback pressure is still very high at remaining production fields.
  • Corn earworm – If chemical controls are needed, they must be applied before larvae move into developing ears.

WEEK 14:

    • The 2nd generation of 12-spot beetles has emerged, and activity will likely remain high through September. Sweep fields with a sweep net to accurately assess population levels. Take a minimum of four samples (ten arcs of the net per sample) from different parts of the field. Beetles tend to concentrate on field edges. At this time of year, adult beetles are pests within snap bean and squash fields. They feed on folliage and developing pods.

     

    • There has been a boom of adult diamondback moths detected in pheromone traps. Development will be rapid under warm temperatures. Intensify field scouting so that treatments can be applied to avoid contamination.

    Read the full pest report HERE and subscribe to receive alert updates.

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WEEK 7:  Flea beetles above, rootworms below, loopers everywhere

Let me explain:
  • Flea beetles invade fields rapidly, and can cause substantial damage to newly emerged leaves. Scouting is simple, thanks to the characteristic leaf damage. See photos and learn more here.
  • Rootworm is the common name for larval Diabrotica beetles. They feed underground, but can be distinguished from maggots by the presence of thoracic legs and a brown sclerotized plate just behind the head.
Rootworm. PHOTO CREDIT: Ken Gray, OSU
  • Cabbage Looper moths continue to be very abundant in the landscape. There is no diapause in this species, so 6-7 generations per year are possible if environmental conditions are suitable. Although trap counts are way above normal, the effect on crops has yet to be determined, and depends on a variety of factors. We will be discussing some of these in the weeks to come.

Read the full pest report HERE and subscribe to receive alert updates.

WEEK 4: Moth movement is low, rootworms in the landscape.

Don’t worry if you’re getting a late start to the planting season. So are the bugs. Many of the pest moth species we track are LOWER than normal for this time of year.

You may start to notice those familiar 12-spot beetles around, particularly on the dandelions in your yard or garden. These are the overwintered females, looking for suitable egg-laying sites (seedling corn, cucumbers, beans).

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