Wednesday, April 29, 2015

Cereal Leaf Beetle in Winter Wheat, Canyon County




Cereal leaf beetle (Oulema melanopus) infestation was identified in winter wheat experimental plots at the University of Idaho Parma Research and Extension Center as well as in surrounding grower fields in Canyon County. The typical feeding patterns, eggs and larvae have been confirmed by Dr. James Barbour, UI IPM Specialist. The first symptoms of infestation became apparent last week. Currently, most plants have at least one leaf with obvious feeding damage. The cereal leaf beetle has a variety of hosts among cereals and grasses with preference to oat, barley, wheat, rye, timothy, fescue, grain sorghum and corn. Substantial crop yield loss and quality decrease can be expected due to lost photosynthetic activity resulting from the feeding damage.

Cereal leaf beetle is a quarantined insect the U.S., which means that the presence of beetles in grain restricts exports to uninfested areas. Fumigation is required to prevent the spread of beetle infestation.

Scouting of fields is vital both before and during the boot stage to assess for cereal leaf beetle presence and damage. It is recommended to scout weekly by walking through the field in a “W” pattern for best coverage. Stop at 5-10 locations depending on field size and examine 10 plants per location. Count the number of eggs and larvae per plant for smaller plants or per stem for larger plants.

 Winter wheat leaves affected by cereal leaf beetle, University of Idaho Parma R&E Center, Parma, ID, April 2015.





Treatment thresholds:  3 larvae per plant and/or 3 eggs per plant before boot stage, and 1 larva per flag leaf after boot stage.



Management-chemical control (From PNW Insect Management Handbook)

  • bifenthrin (BrigadeƆ 2EC and WSB) at 6.4 fl oz/a (0.1 lb ai/a). Apply in spring if one or more eggs or larvae are detected or in late summer if beetles are defoliating seedling stands. Maximum amount allowed 12.8 fl oz/a (0.2 lb ai/a) per season but no more than once every 12 days. PHI 30 days prior to harvest for forage, hay and seed.
  • cyfluthrin (Baythroid XL) at 0.013 to 0.015 lb ai/a. PHI 0 days. REI 12 hr. Maximum amount allowed per 5 day interval is 0.022 lb ai/a. Maximum amount allowed per crop season is 0.089 lb ai/a.
  • lambda-cyhalothrin (Warrior) at 0.02 to 0.03 lb ai/a. PHI 0 days for grazing and forage, 7 days for straw and seed crop. REI 24 hr.
  • zeta-cypermethrin (Mustang MAX) at 0.0175 to 0.025 lb ai/a. PHI 0 days forage, hay; 7 days straw and seed screenings. REI 12 hr. For forage and hay use no more than 0.10 lb ai/a per season; make subsequent applications no closer than 7 days. For straw and seed screenings use no more than 0.125 lb ai/a per season; make subsequent applications no closer than 17 days.

 
Cereal Leaf Beetle eggs. Phillips et al., 2011 (http://jipm.oxfordjournals.org/content/jipm/2/2/C1.full.pdf)   


 
Windowpaning.  One side of the leaf is scrapped off leaving the other side intact and translucent.  This gives the feeding lesion a window-like appearance.  Primarily caused by some young beetle and moth larvae. (University of Kentucky,
http://www.uky.edu/Classes/ENT/530/Exam1slides.ppt. )
University of Idaho CIS on cereal leaf beetle: http://www.cals.uidaho.edu/edcomm/pdf/CIS/CIS0994.pdf



 

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