It’s unusual to find the Florida fern caterpillar in Michigan, especially in February, but that’s what several southwest Michigan growers have found in their Boston ferns. As a group, caterpillars are barely an afterthought in spring floriculture crops. It’s rare to find them and even when we do, they aren’t particularly difficult to control in a greenhouse setting. In areas of the U.S. where they are a frequent agricultural pest, however, Florida fern caterpillars have developed resistance to some insecticides. We won’t go into the biology here, but if you’re interested, check out the Florida fern caterpillar article that Tom Dudek wrote a few years ago. If you have fern baskets hanging in the greenhouse and haven’t examined them in a while, it might be worth the time to send someone up there to inspect the crop.
by Jeremy Jubenville
Managing a Florida fern caterpillar infestation
We've noticed throughout the years that many systemics don't seem to work very well on foliar feeders. The reason for this is, presumably, because they feed primarily on non-vascular tissue where concentrations are likely to be lower. As such, nearly all the recommended management products are contact insecticides and require thorough coverage to be effective. This can be problematic for two reasons:
- Boston ferns have a complex leaf structure with lots of little hiding places.
- Fern baskets are usually hanging up over our heads.
In other words, it’s going to take some time to get the job done.
Dave Smitley from the Michigan State University Department of Entomology suggests the following products: Adept, Bt, Pedestal, Orthene, Mesurol or Duraguard ME. Crop protection products with translaminar activity should provide better results against foliar feeders than those that do not penetrate leaf tissue. You’ll notice that the following table, organized by translocation activity, includes one systemic insecticide. Mainspring (cyantraniliprole) is labeled for use on caterpillars and can be applied through irrigation systems. For growers who dread the thought of spraying all their hanging baskets, cyantraniliprole may be an elegant solution to their dilemma. As always, test a new product on small number of plants before applying it to the entire crop.