ASK THE AGRONOMIST: Foliar Diseases

Posted By Gary Geske

Ask the Agronomist: Foliar Diseases

Read this week’s Ask the Agronomist to learn about which foliar diseases you should be looking for in your fields at this point in the growing season.

Q: Should I be thinking about spraying foliar insecticides yet?

A: We’re about midway through the growing season, and it’s the time of year when leaf diseases and insect pressure prevails.  Watch for these three situations in your corn fields:

  • Northern Corn Leaf Blight
  • Western Corn Rootworm
  • Eye Spot

Also check your soybean fields for Soybean Aphids, and all fields for redheaded flea beetles.

Q: What can you tell us about Soybean Aphids?

A: In last Wednesday’s weekly crop reports, none of our regional sales managers reported soybean aphids at threshold levels but aphid populations can double every two to three days! With the varying stages of soybean development due to an extended planting season and many late replants, continue scouting past your first insecticide application and all the way through pod development.

Q: Soybean Cyst Nematodes are the #1 yield robber of soybeans; are we seeing signs of SCN damage yet?

A: It’s a bit early for Soybean Cyst Nematodes to appear, especially for those late-planted fields and replants. However, farmers can dig roots to check for SCN presence before symptoms can be seen. Digging roots is the best way to monitor fields for SCN, and female SCN will be on soybean roots through early August.

Q: If symptoms aren’t present, why do you recommend checking for Soybean Cyst Nematode females on the roots?

A: Farmers should evaluate effectiveness of their seed treatments all throughout the growing season. The most effective way to manage SCN and many other diseases is by selecting quality soybean seed. At Latham, we urge our growers to consider selecting our unique IronClad™ Soybeans. To bear this brand, every variety must be SCN resistant and have an Iron Deficiency Chlorosis rating of 2.2 or better. It must also contain a Phytophthora-resistant gene as well as a 2.2 or better rating against Brown Stem Rot and either White Mold or Sudden Death Syndrome.

Q: On the corn side, what leaf diseases should farmers be scouting for, especially considering the high-moisture spring and humid summer we have had?

A: Plentiful moisture is ideal for fungal corn diseases. Check your fields weekly for these common diseases:

  • Gray Leaf Spot
  • Southern and Common Rust
  • Northern and Southern Leaf Blight
  • Eyespot

There are confirmed cases of Northern Corn Leaf Blight (NCLB). Now is a critical time to scout fields, especially for fields planted with NCLB-susceptible hybrids. If the disease is present on 50 percent of the field (one or more lesions per plant) at tasseling, a fungicide application may be warranted to protect yield.

Q: In the future, how can farmers lessen their chances of NCBL presence in their fields?

A: To prevent NCLB from becoming a larger problem in the future, rotate to a non-host crop. A two year rotation away from corn may be necessary in no-till and reduced tillage fields with a history of NCBL. Hybrid selection is also key for reducing future threats of NCLB

If you have a question about what you’re seeing in the fields, feel free to ask! Send your questions via Twitter to@LathamSeeds, in a private message on Facebook or call our office at 1-877-GO-LATHAM (1.877.465.2842).

Also be sure to check out TheFieldPosition.com for timely agronomic information. Crop reports From the Field® across Latham’s six-state marketing area are published every Wednesday during the growing season by Latham’s regional sales managers in each of those locations. New articles are posted each week day on our blog. You can even search for “topics” by simply typing key words into the search bar on the upper right-hand corner.

Thanks for tuning in to this week’s Ask the Agronomist. We’ll be back again next week to field all of your questions during #grow16.

Agronomics