Aphids in (Mostly Organic) Tobacco
Several questions on have come in the during the past week about aphids on tobacco. In most cases, these questions were related to management in organic tobacco, where aphids are the most difficult to control pest, or were in tobacco that had not been treated with soil insecticide applications at transplant.
In most cases, green peach aphids (the species present in NC tobacco), are not pests after topping because as leaves mature, they become poorer hosts. If aphid populations develop post topping, they are most often present on suckers.
Therefore, good post topping sucker control is good aphid management. However, organic tobacco a somewhat different scenario. Aphids populations that develop populations pre topping may potentially stick around post topping and may be more difficult to control. There are also far fewer organic aphid management options, few of which are effective. Information on organic and conventional foliar options for aphids are listed in the NC Agricultural Chemicals Manual.
If post topping aphid populations are large, sucker control is not the problem, and growers plan to use insecticides for control, a few key practices will increase their likelihood of success:
- Apply materials using equipment that will cover the entire plant, including the underside of leaves, meaning using drop nozzles.
- Apply materials in a sufficient volume to achieve good coverage. We use 50 gpa water in research trials.
- Make sure that you carefully read the label of your chosen material. Some materials, especially those that are organically acceptable, must be at a specific pH in order to be effective.
- Organically acceptable materials may not function in the same way as conventional materials. A single treatment of recommended conventional insecticides may be sufficient to suppress populations, while organically materials may need to reapplied frequently, perhaps weekly.
One final note, it is unlikely that aphid populations present in fields are exhibiting resistance to soil insecticide treatments applied at transplant given that that these materials are likely no longer present in insecticidal concentrations at this point in the season.