It has been a relative quiet spring for insect questions in tobacco, but last week I received several calls asking about aphid management in tobacco greenhouses. Aphids are an occasional pest in tobacco greenhouses, and the last time I had enough questions about them to warrant a blog post was in 2011. In 2012, more unusual tobacco greenhouse insect concerns were on folks minds.
The first question I always ask agents and growers if they call about aphids in on tobacco plants in the greenhouse is: How far away are you from transplant? For conventional growers, is the most important consideration.
Within 5 days of transplant
If a grower is within 5 days of transplant and plans to use imidacloprid (Admire Pro and generics) or thiamethoxam (Platinum) as a greenhouse tray drench, these treatments should be applied as normal. Either material will control aphids pretransplant at recommended rates (see here for rate information), and no additional treatment will be needed before transplant.
More than 5 days before transplant
If it is greater than 5 days before transplant, acephate (Orthene and generics) is the only material recommended for greenhouse use in tobacco. Imidacloprid or thiamethoxam should not be applied more than 5 days before transplant. If using acephate, growers should consider spot treated only affected trays rather than spraying the entire greenhouse if infestations are not widespread.
For organic growers, options for aphid control are limited both in and out of the greenhouse. Pyrethrins (Pyganic) has some activity and likely the best option in this scenario.