Hi Dinnie –
It is not too late to treat tent caterpillars with Bt-k or spinosad. They are the two most effective, least toxic products available for controlling these destructive pests. I would also recommend that you restrict caterpillar movement and cut off access to feeding areas with Tree Tanglefoot Pest Barrier. If all else fails, apply a fast-acting botanical pesticide as a last resort. Derived from plants which have insecticidal properties, these natural pesticides have fewer harmful side effects than synthetic chemicals and break down more quickly in the environment. They will also reduce the number of caterpillars that will develop into egg-laying adults.
Good luck!
