I planted my large healthy specimen, from a reliable nursery, less than a month ago. Now a handful of branches have round bites on the leaves. (See leaves below.) Please advise.
(I have hort oil, and slug powder, but will wait to hear what you think.)
Thank you or contacting the Toronto Master Gardeners with your inquiry.
Well you have a maurauder with a good set of mandibles! As it turns out your False Indigo most likely came along with eggs belonging to either the Wild Indigo , Hoary Edge, Southern Dogface or Genista caterpillars. These all find the False Indigo very palatable. So upon close examination you should find either active feeding caterpillars, or possibly chrysalis if they have moved on to that stage; or other evidence such as possible webbing or droppings on leaves. While many of these caterpillars are considered pests, they are also recognized as pollinators.
If you did not intend on having a pollinator garden, you can take one of several strategies to manage your hungry visitors;
i. Manually pick off the observed intruders, depending upon how many bushes you have, this is usually sufficient control on perennials.
ii. Apply an organic pesticide, such as Btk Sprays (Bacillus thuringiensis subspecies kurstaki) which is a microbial insecticide that kills only caterpillars. It’s safe to use near bees, beneficial insects, and wildlife. It will however also kill preferred species such as Monarchs if they happen to ingest the pesticide. Caterpillars must feed on treated leaves to be affected. Because it’s most effective on small, newly hatched caterpillars and breaks down rapidly, treatment timing is critical.
You can find several brands of BT such as Safers, sold in most garden centers or RONAs ECO BioInsecticide, etc.
Here are some links for further reading:
https://ipm.ucanr.edu/QT/lfcaterpillarscard.html
https://growingsmallfarms.ces.ncsu.edu/growingsmallfarms-genistacaterpillar/
https://hgic.clemson.edu/factsheet/baptisia-false-or-wild-indigo/