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      Oklahoma Sorghum: Chinch Bug, Corn Leaf Aphids Are Plentiful

      Sorghum producers were careful in selecting sorghum hybrids to grow that have resistance to sugarcane aphid. They have also been vigilant in scouting their fields for buildup of sugarcane aphids this year. Their reward has been lower numbers of sugarcane aphids being present in their fields, and fewer acres needing treatment.

      However, this summer has been one for the books with regard to chinch bugs and corn leaf aphids. Both have been very active in sorghum this year.

      Chinch bugs are noticeably active and they are causing some injury to sorghum plants. Unfortunately, their habits make them very difficult to control. They prefer to live at the base of the plant and lay eggs behind the lower leaf sheaths. Upon hatching, nymphs live in the space between the stalk and the leaf collar.

      I have been asked, “Why do we have so many chinch bugs in sorghum this late in the year?” My best answer is that they are simply increasing because Mother Nature provided optimal conditions for them to reproduce without their normal population “checks” which includes the fungal pathogen Beauveria bassiana. We typically see population numbers cycle over a 7-10 year period.

      Chinch bug management is difficult under any circumstance. Insecticide control on mature plants is often ineffective. Why? For two reasons: the spray is difficult to cover the lower parts of the plant, and most insecticide active ingredients do not move through the leaf tissue, so the nymphs can avoid exposure to the insecticide.

      If close to harvest, do so as soon as possible, because chinch bug feeding can weaken stalks, making them more prone to lodging. For late-planted sorghum intended for a dual crop, insecticide treatment is suggested when chinch bug numbers reach 50 per plant. Apply registered insecticides at the full-recommended rate, delivered in at least 20 gallons of water per acre.

      Use either cone nozzles designed to provide high pressure for canopy penetration or through double-swivel drop nozzles targeted to the base of the plant. Morning applications are most effective because that is when the bugs are more exposed. Check OSU Current Report CR-7170 Management of Insect and Mite Pests of Sorghum for suggested insecticides.

      What about Corn Leaf Aphid?

      Corn leaf aphids are also very prevalent in sorghum, usually in the whorl. They can build into large numbers, and they produce honeydew. Control of corn leaf aphids seldom is justified.

      While they can “make a mess” in a sorghum whorl, research out of Texas suggests that they rarely cause significant yield loss and they serve as a great source of food to attract natural enemies such as lady beetles, lacewings, syrphid larvae and parasitic wasps.

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