Additional Information on Stripe Rust Fungicides, Other Diseases, & Cereal Leaf Beetle

Randy Weisz, Small Grains Specialist, is providing additional information on stripe rust and other diseases – see his information below:

Stripe Rust & Fungicides: Questions are coming in about using protectant strobilurin fungicides to prevent the wheat crop from stripe rust, as an alternative to watching for a stripe rust hot spot and then spraying a triazole containing fungicide. A strobilurin fungicide will protect a wheat plant from fungal infection as long as it continues to cover the tissue. This could be as long as several weeks. If there is lots of rain the time frame may be shortened. If the plants are actively growing the time frame may be shortened. As of this week, much of the NC wheat crop has not headed out and some acres don't even have the flag leaf extended. I talked with a grower a few days ago who had just barely two joints on his wheat. Additionally, the weather continues to be cool and wet. Growers in this situation could see four to six more weeks of important growth before the crop is made. If they sprayed a protective fungicide now (in mid April), it might run out while the crop is still at risk to stripe rust.

Other Diseases: Current weather conditions are also ideal for the development of Powdery Mildew. So far we have seen little to no Powdery Mildew in the wheat crop but it could develop over the coming weeks.

Cereal Leaf Beetle: We are just starting to see cereal leaf beetle larvae at very low numbers. It appears to be too early to spray for cereal leaf beetle, but another 10 days or so might see more larvae in the crop.

Recommendations: If a grower has stripe rust in a field, or powdery mildew covering 5% of the upper leaf area, or large Cereal Leaf Beetle larvae s/he needs to spray whenever that happens. But at this time, most growers will not be in that situation. Given the extended growing season it looks like we might have… if a grower wants to spray a protectant pesticide (either for disease or cereal leaf beetle) it might be best if they hold off for another 10 to 14 days and then consider which chemistries are still on label given the growth stage their wheat is in at that time.

The fungicide table can be found on-line at:
http://www.smallgrains.ncsu.edu/_Pubs/Xtrn/FungicideTable.pdf