Weeds have continued to develop despite the inclement weather. The saturated soil will make it difficult for ground application equipment to apply herbicides in the near future, particularly in southern Iowa. Thus, growers and agrichemical dealers are considering the use of aerial applications to deter weed interference. However, there are several important considerations that should be made prior to making an aerial application.
The first is whether or not the herbicide that has been selected can legally be applied with aircraft. A second consideration is whether or not the weeds and crop are within the guidelines suggested by the label. In most cases, the weeds are probably larger than the label stipulates and thus control expectations must be reconsidered. And third, herbicide drift potential must be evaluated. Drift typically is greater with aerial equipment compared with ground equipment, but with either type of application, drift management is imperative. See the table for herbicides that can be legally applied with aerial equipment. According to the Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA), unless a pesticide is specifically restricted for a particular application technique, and if the application technique is a standard practice, the pesticide can legally be applied in that manner. Also, with the recent high humidity and temperature, herbicides are likely to be extremely active. Choice of rate and adjuvant will be important considerations when attempting to optimize weed efficacy and minimize crop phytotoxicity.
| Herbicide |
Aerial application |
Comments |
| Soybeans Assure II |
Yes |
Assure II is rainfast within 1 hour of application. Do not use vegetable-based adjuvants. |
| Basagran |
Yes |
Apply when weeds are within the label restrictions. Basagran is labeled for rescue treatments for common cocklebur and velvetleaf. |
| Blazer, Status |
Yes |
Observe the weed size restrictions on the label. Apply within 50 days of soybean harvest. Soybean injury is likely. |
| Classic |
Yes |
Classic can be applied to actively growing weeds after the first soybean trifoliate until 60 days before harvest. |
| Cobra |
Yes |
Observe weed size listed on the label. Apply until 45 days prior to harvest but not after soybeans have reached R6 (full seed) stage of development. Soybean injury is likely. |
| Concert |
Yes |
Apply after the first trifoliate has fully expanded but no later than 60 days prior to harvest. |
| Flexstar, Reflex |
Yes |
Apply to actively growing weeds within the labeled size restrictions. Apply prior to soybean bloom. |
| Fusilade |
Yes |
Apply to actively growing weeds within the labeled size restrictions. Apply prior to soybean bloom. |
| Fusion |
Yes |
Apply to actively growing weeds within the labeled size restrictions. Apply prior to soybean bloom. |
| Galaxy |
Yes |
Do not apply by air if sensitive plants are within 200 feet. Do not apply within 50 days of harvest. Do not apply to stressed soybeans. |
| Pinnacle |
Yes |
Apply after the first trifoliate has fully expanded but no later than 60 days before harvest. The use of crop oil concentrates increase the potential for soybean injury. |
| Liberty |
Not restricted |
Do not apply within 70 days of harvest. |
| Poast Plus, Prestige |
Yes |
Apply to actively growing grasses within the recommended stage of growth indicated on the label. Do not apply if rain is expected within one hour following application. Do not apply to soybeans within 75 days of harvest. |
| Pursuit |
Yes |
Apply prior to soybean bloom. Do not apply within 85 days of harvest. |
| Resource |
No |
Do not apply within 60 days of harvest. Apply to actively growing weeds within the size recommendations contained in the label. Resource is registered for a rescue application on tall (up to 30 in.) velvetleaf. |
| Rezult |
Yes |
Apply when weeds are small and actively growing. There are not restrictions on crop size. Do not apply within 75 days of harvest. |
| Roundup Ultra |
No |
Ground application only. May be applied through full flowering stage of soybean development. Observe precautions for drift management. |
| Scepter |
Yes |
Do not apply within 90 days of soybean harvest. Apply to actively growing weeds within the size recommendations suggested on the label. |
| Select |
Yes |
Apply prior to 60 days before harvest. Do not apply under conditions that cause stress on the soybeans and weeds. |
| Stellar |
No |
Apply to actively growing weeds within the size restrictions on the label. Do not apply after pod-set or within 60 days of soybean harvest. |
| Synchrony STS, |
Yes |
May be applied after the first trifoliate has opened but no later than 60 Reliance STS days before soybean harvest. Apply to actively growing weeds within the recommended growth stage. Use only on soybean varieties designated as STS in the variety name. |
| Corn Aatrex, Atrazine |
Yes |
Apply before broadleaf weeds are 4 in. in height, grasses exceed 1.5 in., and corn 12 in. |
| Accent |
Yes |
Apply broadcast on corn up to 24 in. in height or exhibiting 6 or fewer leaf collars. Use drop nozzles for corn from 24 to 36 in. or exhibiting 10 collars. |
| Banvel, Clarity |
Yes |
Extreme caution must be taken to eliminate drift. Clarity is less prone to volatilization. Soybeans and ornamentals are extremely sensitive to dicamba. Use drop nozzles on corn taller than 6 in. (ISU recommendation). |
| Basagran |
Yes |
Apply when weeds are within the label restrictions. Basagran is labeled for rescue treatments for common cocklebur and velvetleaf. |
| Basis |
Yes |
Apply to corn from spike to 2 collars. Application to larger corn will increase injury potential. |
| Basis Gold |
Yes |
Apply to corn up to 12 in. in height. Do not apply to corn with 6 or more collars. |
| Beacon |
Yes |
Apply broadcast when corn is from 4 to 20 in. in height. Can be applied to corn taller than 20 in. to tassel with drop nozzles. Do not apply after tassel. |
| Bicep (all formulations) |
Yes |
Apply before weeds are past the 2-leaf stage and corn exceeds 5 in. in height. Directed applictions can be made to corn from 5 to 8 in. in height. |
| Bladex |
No |
Apply before corn is in the 5-leaf stage but before weeds are 1.5 in. tall. Crop injury is likely when conditions place the corn under stress such as cool, wet conditions. Do not apply the 4L formulation postemergence. |
| Buctril, Moxynil |
Yes |
Apply to corn between the 3-leaf stage and tassel emergence. |
| Buctril + Atrazine, Moxynil + Atrazine |
Yes |
Apply to corn between the 3-leaf stage and 12 in. in height. |
| Contour |
Yes |
Apply before the corn reaches 12 in. in height. Apply only to imazethapyr-resistant hybrids. |
| Exceed |
Yes |
Apply to corn from 4 to 30 in. in height. Use drop nozzles when corn is 20 in. or taller or exhibits 6 collars (V6). |
| Extrazine II |
No |
Apply before the corn is in the 5-leaf stage but before corn exceeds 12 in. in height. Crop injury is likely when conditions place the corn under stress such as cool, wet conditions. Do not apply the 4L formulation postemergence. |
| Hornet |
No |
Apply to corn that is from 3 to 24 in. in height. May be applied to larger corn as a directed spray. Weeds, depending on the species, should be from 2 to 8 in. in height. |
| Laddok S12 |
Yes |
Do not apply after the corn exceeds 12 in. in height. |
| Liberty |
Not restricted |
Apply until corn is 24 in. tall or in the V-7 stage of development. Do not apply within 60 days of harvest. Do not add surfactants. Apply only to Liberty Link hybrids. |
| Marksman |
Yes |
Apply from corn emergence through the fifth-leaf stage but before corn reaches 8 in. in height. |
| Permit |
No |
Apply over the top or with drop nozzles from spike through layby stage of corn development. |
| Poast Plus, Prestige |
Yes |
Apply postemergence when weeds are actively growing and at the label recommended growth state. Use only on SR or Poast Protected hybrids. |
| Pursuit |
Yes |
Apply postemergence to weeds within the suggested heights but before the corn exceeds the 8-leaf stage. Use on imazethapyr-resistant hybrids only. |
| Resolve |
Yes |
Apply postemergence when weeds are actively growing and within the suggested size restrictions on the label. Do not apply in the vicinity of sensitive plants if the corn is more than 12 in. tall, soybeans are more than 10 in. tall, or have begun to bloom. |
| Resource |
No |
Apply postemergence to corn from the 2-leaf stage through the 10-leaf stage of development. Do not apply when weeds and corn are under stress. |
| Roundup Ultra |
No |
Apply to Roundup Ready corn hybrids only up to 24 in. in height. |
| Scorpion III |
No |
Apply over the top of field corn up 8 in. in height. May be applied to taller corn as a directed spray or with drop nozzles. |
| Sencor |
Yes |
Sencor must be used in combination with one of the registered products. |
| Shotgun |
Yes |
Apply from spike to the 5-leaf stage of corn development but before corn exceeds 12 in. in height. |
| Spirit |
Yes |
Apply to corn between 4 and 24 in. in height. Use drop nozzles to improve coverage when corn is taller than 20 in. or exhibits 6 collars (V6). |
| Stinger |
No |
Apply after emergence until corn is 24 in. in height. Stinger works primarily on weeds in the sunflower family, such as common cocklebur and giant and common ragweed. |
| 2,4-D |
Yes |
Apply when weeds are small and before the corn is 8 in. in height. Application to taller corn should be done with drop nozzles. Preharvest applications can be done after the corn has reached dent stage of development. |
| Tough |
Not restricted |
Apply to actively growing weeds. There are no restrictions on corn size. Observe restrictions for the tank mix companions. |
