Statewide
Fungicides are typically used in grain sorghum to control foliar disease when the potential for yield loss is significant. However, some suggest fungicides should be used to improve “plant health”, regardless of disease presence. This preemptive application is thought to improve physiological function of the plant, improve stress tolerance and standability of crop. The actual benefits of these applications are uncertain.
Texas A&M AgriLife has conducted several on-farm trials over multiple years on the Upper Gulf Coast of Texas to evaluate fungicide use in grain sorghum. Trials include several strobilurin type fungicides. Headline (6 oz/ac), Topguard (14 oz/ac), Quadris (6 oz/ac), Quilt (14 oz/ac) and Quilt Xcel (10.5 oz/ac) were applied in early bloom stages and compared to untreated checks. Plant health measurements included SPAD readings (leaf greenness), leaf temperature, and lodging along with yield, grain moisture, and test weight. Disease was present at most test locations but at very low levels of severity. None of the tested products produced measurable differences in plant health or yield. Lack of yield response certainly limits justification for application of the fungicides, given disease presence and severity was low.
Similarly, trials at the University of Nebraska evaluated the effects of several strobilurin fungicides, including Headline (6 oz/ac), Quadris (6 oz/ac), Quilt (14 oz/ac) and Quilt Xcel (10.5 oz/ac) applied at early flowering. The fungicide applications did reduce the incidence of disease (leaf spot and bacterial leaf stripe) compared to untreated checks, although severity levels were very low overall. They also showed that the fungicide treatments improved plant greenness or stay green. However, the fungicide treatments did not increase yield or test weight compared to untreated checks and did not affect moisture at harvest. In the end, the plants looked better but did not yield better.
Bottom line. Only apply fungicides when disease is present and has crossed established agronomic and economic thresholds. Strobilurin fungicides are very effective in controlling labeled diseases. Fungicides applied to improve plant health may result in a “better looking” crop. However, the applications are not justified if disease is not present and significant yield losses are not eminent.
If you have questions about grain sorghum and plant health, consult our Texas A&M AgriLife plant pathologists working in grain sorghum: Dr. Gary Odvody, Corpus Christi; Dr. Tom Isakeit, College Station; Dr. Ron French, Amarillo.
This tip was submitted by Dr. Ronnie Schnell, Ph.D., ronnie@ag.tamu.edu (Cropping Systems Specialist, Texas A&M AgriLife Extension – College Station) and by Dr. Dan Fromme, Ph.D., d-fromme@tamu.edu (Extension Agronomist, Texas A&M AgriLife Extension – Corpus Christi)
