There are many different seed treatments available for wheat (see table at the end of this article). Although most seed treatment ingredients are fungicides, lindane and imidacloprid are insecticides. Each ingredient has certain strengths and weaknesses that may depend on the particular rates used. Many commercial formulations are complementary combinations of ingredients to provide a broader spectrum of protection. Carboxin, difenoconazole, imazalil, imidacloprid, metalaxyl, tebuconazole, thiabendazole, and triadimenol are systemic whereas the others are surface-acting protectants.
A major use of seed treatments is control of seedborne smuts and bunts. Loose smut control requires a systemic fungicide such as carboxin, tebuconazole, difenoconazole, or triadimenol. Common bunt can be controlled with most commercial treatments. Recently, a disease called Karnal bunt was detected in the southwestern United States. Quarantines are established to keep Karnal bunt out of the Great Plains. The use of certain seed treatments could help reduce the spread of this seedborne disease. No products can control Karnal bunt after it becomes established in the soil.
A second major use is to improve stand establishment. Most treatments do at least a fair job of controlling seed rots and seedling blights. Scab and black point are two seedborne diseases that can reduce seed germination. If seed has either of these diseases, it should be cleaned to remove all light seeds, then tested for germination rate. If germination is low (less than 90 percent), a seed treatment could help raise the germination rate. Several treatments are available if wireworms are expected to be a problem in stand establishment.
Some common wheat seed treatments in Kansas 1997-98
A E = excellent, G = good, F = fair, S = low level suppression, - = not recommended or insufficient information, (H) = hopper box treatment.
B Dryland foot rot (also called Fusarium crown rot), common root rot, or Rhizoctonia root rot.
C Powdery mildew, Stagonospora nodorum leaf blotch, or leaf rust controlled in the fall. Control may or may not carry through to spring depending on year.
D Greenbugs, Russian wheat aphids, English grain aphids plus bird cherry-oat aphids and BYDV (barley yellow dwarf virus), which they carry.
E Dividend now combined with Apron to improve control of Pythium seed rot and seedling blight. Hopper box formulations available.
F Fall control of insects and BYDV depends on rate. Use high rate for best control. Control may or may not carry through to spring depending on year.
G RTU-Vitavax Thiram (6.8 fl. oz./cwt) must be combined with RTU-PCNB (3.0 fl. oz./cwt) for reduction of seedborne Karnal bunt teliospores.
Information provided by Robert Bowden, Kansas State University Plant Pathology Extension.