Aphids showing up on winter and spring wheat     | Printer-Friendly Format |

BROOKINGS, SD - Winter wheat and spring wheat must be scouted for aphids as soon as possible.

There are reports of significant aphid infestations from Brown, Davison, Faulk, Hand, Hughes, Hyde, Jerauld,
Roberts, and Sully County.

Ray Gosmire, Davison County Agronomy Educator reported last Tuesday (May 29) that some wheat growers
in Davison County have already started spraying for aphids.

Gary Erickson, Brown County Agronomy Educator reported last Friday (June 1) that he was finding aphids in
most winter and spring wheat fields that he had inspected; Erickson predicts that economic threshold levels of
five bird cherry-oat aphids per tiller may be reached by the time the winter wheat reach the flowering stage.

Aphids are insects with syringe-like mouthparts and feed on the sap of plants.  Although small in size (1/16 to
1/8 inch), they multiply very fast and their collective feeding can reduce crop yields.  They are also known to
transmit diseases such as barley yellow dwarf virus.

The two aphid species currently being found on wheat in SD are the bird cherry-oat aphid and the English
grain aphid.  Bird cherry-oat aphids are dark olive green and broadly oval in form; English grain aphids are
bright green in color, with dark skinny legs, antennae, and cornicles or “tail pipes.”  Bird cherry-oat aphids
can be found mainly underneath the leaves while English grain aphids congregate on the head at flowering.

The economic thresholds for bird cherry-oat aphids are 20 aphids per tiller during the seedling stage, 30
aphids per tiller from boot to heading stage, 5 aphids per tiller during the flowering stage, and 10 aphids
per tiller from milky ripe to dough stage.  The economic thresholds for English grain aphid are similar to the
bird cherry-oat aphid except for seedling and boot to heading stages when its economic thresholds are 30
and 50 aphids per tiller, respectively.

Insecticides labeled for use against aphids on wheat in SD and their recommended rates and pre-harvest
intervals (PHI) are as follows:  Baythroid XL (1.8 to 2.4 fluid ounces per acre, 30 day PHI); Lorsban 4E
(0.5 to 1.0 pint per acre, 28 day PHI); Mustang Max (3.2 to 4.0 fluid ounces per acre, 14 day PHI);
Penncap-M (2 to 3 pints per acre, 15 day PHI); Proaxis (2.56 to 3.84 fluid ounces per acre, 30 day PHI);
Warrior (2.56 to 3.84 fluid ounces per acre, 30 day PHI).  Always read and follow label directions.

Links to University of Nebraska Entomology:  Biology | Economic Thresholds

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 Web Posted on Monday, June 4, 2007 by Mike Catangui. Last Updated on Monday, June 4, 2007.