Asking About Organic Aphid Management in Tobacco
I have recently received a few question about organic aphid management in tobacco, specifically about efficacy of different foliar insecticides. We have done a fair amount of work on organically acceptable insecticides in tobacco, including work on tobacco flea beetles and caterpillar pests, but aphid management with these materials is particularly difficult. Organic materials act differently than conventional materials, and waiting to treat until 10% infestation is likely inappropriate for organic materials.
Therefore, I suggest that organic growers manage aphids as follows:
1. Scout fields at least weekly until topping.
2. When reproducing aphid populations are observed (large wingless aphids are observed surrounded by small wingless aphids), begin treatments of your chosen material (more on that below). Only the upper 1/3 of leaves need to be observed for aphids.
3. Continue with treatments on a weekly basis until aphids are no longer observed or until topping, whichever comes first.
4. Top as soon as feasible. Consider making several topping passes through a field, if feasible.
In regards to selecting a material, because all of them have had essentially marginal activity in our experiments, I’m not too enthusiastic about any of them. Organically acceptable materials recommended for use in tobacco are indicated as OMRI listed in the NC Agricultural Chemicals Manual. At this time, we probably get the best aphid control through topping, which hardens off the leaves, and subsequent contact applications.