LIMITS ON LATE WILD OAT HERBICIDE APPLICATION IN WHEAT

Delays in controlling wild oat in spring wheat may have occurred due to adverse weather conditions or other reasons. The following are the wheat and wild oat stage limits for post-emergence applied wild oat herbicides:

 

Wheat

Wild oat

Assert

up to jointing

4-leaf

Avenge

prior to flag leaf emergence

5-leaf

Achieve

up to boot

6-leaf

Puma

6-leaf (prior to jointing)

2-tiller

Tiller

up to 6-leaf (HRS only)

2-tiller

Cheyenne

end of tillering or 6-leaf (HRS only)

4-leaf

Hoelon

up to 4-leaf

4-leaf

Refer to herbicide labels and NDSU Extension Service circular W-253 '2000 ND Weed Control Guide' for required information on use.

LEAF RUST PRESENT IN WINTER WHEAT

Low levels of leaf rust were found in an area (Stutsman County) winter wheat field on June 1. Producers are encouraged to monitor winter and spring wheat fields for leaf rust, especially if susceptible varieties are grown. Most winter wheat varieties are susceptible to leaf rust, with the exceptions of Elkhorn (moderately resistant) and Ransom (resistant). Spring wheat varieties rated as susceptible to leaf rust include 2375, AC Barrie, 2398, and McNeal. Numerous other varieties are moderately susceptible to rust. Refer to NDSU Extension Service circular A-574 ‘2000 ND HRS and HRW wheat variety selection guide’ for leaf rust and other foliar disease ratings.

What impact does leaf rust have on yield? Based on Kansas State University data, wheat in the flowering stage with 10% severity on the flag leaf is predicted to cause 10% yield loss, 40% severity may cause 20% yield loss, and 100% severity may cause 35% yield loss. As wheat reaches later growth stages the impact of leaf rust on yield is reduced. For example, at the soft dough stage, 10% rust severity on the flag leaf is predicted to cause 1% yield loss, 40% severity may cause 4% yield loss, and 100% severity may cause 10% yield loss.

If use of a fungicide appears economical, refer to NDSU Extension Service circular PP-622 '2000 Field Crop Fungicide Guide' and fungicide labels for product selection and use.