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Controlling the Sunflower Moth

Monday, March 26, 2018
filed under: Disease

Wherever sunflower is grown in Texas and the southern High Plains, a standard and essential part of managing the crop is controlling sunflower (head) moth. “This insect is probably why half the farmers should not consider sunflower,” notes Calvin Trostle, Texas A&M Extension agronomist, Lubbock. “I know that might be the wrong thing to say; but too often, new farmers to sunflower are not diligent in scouting at initial bloom. Or, they wait too long to spray.”
       Sunflower moth alone is not the complete story. When moth pressure and larval feeding is moderate, then damage to the sunflower head might be mild. But the same larval damage may result in the opportunistic Rhizopus head rot fungus infection, which can devastate yields.
       Ed Bynum, Texas A&M AgriLife Extension entomologist, Amarillo, agrees. “Sunflower moth is manageable. We know when to scout, what to look for, what to spray, how to get thorough coverage, and especially pinpointing the timing,” Bynum observes.
       Currently, for Texas sunflower areas and other southern High Plains regions, the recommended initial spray is based on a threshold of “presence” in the field — not a specific number of moths per five heads. “That timing for traditional pyrethroids has typically been at 10-20% bloom; or better stated, when 10-20% of the heads in the field are at any stage of bloom,” Bynum says. That includes heads that just opened that morning and a few florets with pollen around the outer rim.
       Trostle shares that since the 1990s, the sunflower industry in Texas has often stated, “If you have sunflower moth damage, then you probably sprayed too late.” What has evolved since then is that the technical spray based on Extension research may be 10-20% field bloom — but the practical recommendation may be to make the spraying decision a day or two sooner to ensure that sprays are timely.

A sunflower moth larva feeds on an immature confection sunflower seed.
(Photo: Calvin Trostle)

       In the past seven years or so, new products like Dupont’s Prevathon® (active ingredient chlorantraniliprole) and also an ingredient in Syngenta’s Besiege®, which is a mix with a pyrethroid) target the larval stage, but leave beneficial insects alone. This is good from the aspect of preserving pollinators (many species of bees), and that is environmentally — and publicly — beneficial. (As of 2018, Prevathon is now a product of FMC.)
       Though farmers often focus on which insecticide to use, Trostle and Bynum both steer the discussion back to timing. “What chemical you use might in fact be your third most important control decision for sunflower moth. Timing is first,” Trostle emphasizes.
       “Then we want farmers to ask, ‘Well, then what is second?’ Coverage! Poor coverage leads to poor control.”
       Both Texas Extension specialists note they are uneasy about some chemical labels permitting only 2.0 gal/ac carrier volume for aerial application. “A minimum of 3.0 gal/ac is better, and you may consider more than that — even if you need to pay the spray service an extra $1.00/ac,” Trostle suggests.
       “If you can spray with a ground rig, that is best. But it takes more time, and sacrificing timing may not be the right decision,” he adds.
       Recent National Sunflower Association-funded research conducted by Trostle, Bynum and Colorado State University Extension specialist Ron Meyer, Burlington, compared several products and timing (including pre-bloom sprays of Prevathon and Besiege, which some field chemical company staff were recommending), and one or two sprays.
       The primary conclusion emanating from six research sites over 2016 and 2017 in Texas and Kansas suggested there was never a benefit from a pre-bloom spray for chlorantraniliprole; and sometimes, sunflower moth control was reduced. The project’s staff tore apart several thousand heads while counting worms for the basis of this conclusion.
       For further resources on sunflower moth control (and other insects), consult the Texas A&M AgriLife Extension’s “Managing Insect Pest in Texas Sunflower,” E-479, click here.
       The Kansas State University guide to sunflower moth control can be found here.
       Producers and insect scouts who wish to learn more about sunflower bloom staging in relation to sunflower moth scouting and spraying are encouraged to review the sunflower growth stage and bloom guide at the above TAMU webpage.
       “Even though I am an agronomist, I have spent more time ‘cussing and discussing’ sunflower moth control with farmers than any other topic,” Trostle says. “But it may be the first thing a prospective first-time grower in the southern High Plains must understand before he or she plants sunflower.”
         Trostle notes that Dakota entomologists now report some sunflower moth in some years, and he recommends that growers in that region defer to their own state extension entomologists.