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Soybean Aphid Management in Ohio
Last year, parts of Wyandot County had very heavy infestations of Soybean Aphids. According to Ohio State University Specialists Ron Hammond and Bruce Eisley, as well as information gathered from the experiences of numerous researchers, extension agents, and consultants throughout the Midwest, the following guidelines should be used in determining the need for an insecticide application for soybean aphids.
Sampling for the soybean aphid should begin in mid-to-late June, and definitely be on-going during the R1 to early R2 (flowering) growth stages. Sample the upper leaves from 4-5 plants from 20 locations in the field, and rate the aphid infestation on a scale of:
0 = none
1 = 1-10 per single leaflet
2 = 10-30 per single leaflet
3 = 30-100 per single leaflet
4 = 100-300 per single leaflet
5 = >300 per single leaflet
An average rating of 3 or higher across the field suggests that soybean aphids are common and abundant, and treatment should be considered. At a rating of 3 or higher, you will probably also find aphids on the petioles and stems that suggest an increasing population. If honeydew is present in the field and noticeable, the aphid population is probably high.
Timing of the insecticide application will be very important in achieving good control. The current thought is that the late vegetative stages prior to flowering will be too early to spray. Other states have seen a rebound in aphid densities when an insecticide is applied this early because of the reproductive capabilities of the remaining aphids. However, detecting an early infestation in late June will alert growers to potential problems.
Most insecticide applications should occur in early to mid July during flowering or immediately thereafter. Observations from other states suggest that the greatest benefit from an insecticide application will come during this time period. The later in the summer an insecticide application is made, the less the benefit from that spray. Spraying late in the season after pods have filled or following dispersal of winged aphids in mid-to-late summer will be too late to prevent economic yield loss. During those times, an insecticide application will fall into the revenge category, and do little good.
The current thought, among Hammond and Eisley, is that best control will occur using ground equipment. Good coverage is essential and will be best achieved by spraying with higher pressures and higher gallons per acre. The following insecticides are labeled for soybean aphid control, although additional ones might be labeled later. The current insecticides are Asana XL (5.8 to 9.6 fl oz per acre), Furadan (0.25 to 0.5 pt per acre), Lorsban 4E (1 to 2 pts per acre), Mustang (3.4 to 4.3 fl oz per acre), Penncap-M (1-3 pts per acre), and Warrior (1.92 to 3.2 fl oz per acre).
Care should be taken during flowering if bees are actively working a soybean field. Although bees are not usually associated with soybeans, they do forage in soybeans and problems could occur if hives are nearby. Label directions pertaining to most of the insecticides and state regulations state that the insecticide should NOT be applied to blooming or flowering crops if bees are actively working in the target area. Thus, most materials for soybean aphid control should be applied in early morning or late day when bees would not be active in fields.
Also, Ohio regulations state in 901:5-11-04 of the Ohio Administrative Code "No pesticide which is required to carry a special warning on its label indicating that it is especially toxic to honey bees, shall be dispensed over an area of one-half acre or more in which the crop plant is in flower unless the owner or caretaker of any registered apiary located within one-half mile of the treatment site shall be notified by the person who applies for himself or engages a pesticide applicator no less than twenty-four hours in advance of such intended treatment; provided, however, that these locations are registered and identified as required by section 909.02 of the Revised Code of Ohio, and that such apiary locations have been posted with the name and telephone number of the owner or a responsible caretaker". The names and addresses of registered apiaries are available at the Ohio Department of Agriculture at 1-800-282-1955.
Growers should be advised to follow all label directions and state regulations; it is the soybean grower's responsibility!
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