"Snowball" Viburnum caterpillars ... after they aren't visible anymore
History of the problem: The bushes were cut down to 2" woody (1-2" diameter) in 2014. They are now grown up to 4' branches with lots of leaves, few flowers. Leaves were attacked by white caterpillars which I hand picked and soap-sprayed (mostly underside of leaves). And, I spoke w/ an expert by telephone in mid-May, who recommended insecticidal soap (done repeatedly) and tanglefoot wrap (not in any stores in my area and caterpillars are already 'gone') and horticultural oil spray when eggs are visible (April).
So Now: Is it too early to use the horticultural oil spray (no beetles are visible, I haven't dug into soil to verify if they are there pupating). Is there anything else to do at this point? And incidentally; is Tanglefoot allowed in S.E. Michigan? A helpful clerk suggested it was, at one point, not allowed as it is dangerous for birds. He suggested painting a band of 'tree wound' around the base of branches to trap the caterpillars but I don't see them anymore, I think that window of opportunity may have passed.
Many thanks for help with this, in all stages of viburnum beetle life.
Tanglefoot tree barrier is not prohibited in Michigan. If you cannot find it in a store near you, there are alternative ways to create a protective band on your viburnum: http://fyi.uwex.edu/gypsymothinwisconsin/making-a-sticky-barrier-band/
If you do not see any of the larvae or the beetles on your viburnum presently, no treatment is recommended unless you decide to use a systemic insecticide containing Imidacloprid as the active ingredient. It is not recommended to apply this product until after blossoming is complete and all the petals have fallen. For more information about appropriate products and their timing, please refer to this factsheet: http://www.hort.cornell.edu/vlb/manage.html
Finally, you may find this article written several years ago about this pest helpful also: http://msue.anr.msu.edu/news/viburnum_leaf_beetle_now_in_michigan
A BIG Thank you for your advice. I will follow the recommended link for an alternative way to 'create my own tanglefoot'. HOWEVER, now the larva are gone (gone to the soil perhaps?) but it appears that there are small outcroppings of ants (not everywhere, just near some leaves not skeletonized by the caterpillars) 'herding' some tiny critter, almost like aphids. Would these be a part of the V. beetle issue, or something else that may have come now?
The beetles may well be pupating in the soil.
The small 'critters' may be aphids, thrips or spider mites. It sounds like neither the ants or other 'critters' are in high enough numbers to warrant treatment at this time. Plus, it sounds like the ants may be controlling the 'critter' population.
Please continue practicing your excellent observation skills to make sure that the 'critter population does not get large enough to cause serious damage. For more information about these pests, I'll share one more fact sheet for you to peruse: http://www.clemson.edu/extension/hgic/pests/plant_pests/shrubs/hgic2057.html