I have an herb garden and there is something that looks like foam on my parsley, lavender, hyssop, sage and bergamot. I have tried some herb friendly insecticidal soaps, but it still comes back. Do you have any suggestions as to what this may be and how to get rid of it?
It sounds like spittlebugs have moved into your herb garden. The telltale sign being the foam that you mention. In addition to garden plants, spittlebugs are also frequently found in pine trees.
During the nymph stage of their life cycle these little bugs attach themselves to a plant’s stems and create a frothy home where they hide until emerging as an adult. As a nymph the spittlebug is vulnerable to drying out and predators. This froth provides them with moisture and a protective covering. To make the spittle, nymphs position themselves upside down on a stem, ingest plant juice and then excrete it along with air to form tiny bubbles.
The adult spittlebugs are less obtrusive. After several molting periods they will appear in late summer. They are about 1/8 to 1/2 inch long with hard brown bodies and live in lush grasses. They have the ability to hop quite a distance and are often mistaken for leafhoppers.
Spittlebugs won’t cause much damage to your plants although sometimes they can transmit leaf curl disease, which is unsightly but not fatal. In such cases damaged leaves should be removed and thrown in the trash not the compost bin. That being said, an infestation can be hard to work around especially in an herb garden where you will want to harvest leaves and stems on a frequent basis.
Because you are dealing with plants that are edible, I suggest you use natural pesticides in your battle with this pest. During the nymph stage, while the body of the insect is still soft, dusting with diatomaceous earth can be effective. Diatomaceous earth is basically fossilized algae. It acts as both an abrasive and desiccant against the spittlebug, breaking down its outer coating and drying the insect out. Select natural diatomaceous earth and not swimming pool grade (used as a filtering agent) because swimming pool grade is chemically treated.
Both nymph and adult spittlebugs can be eliminated with a pyrethrin-based product. The active ingredient in this pesticide is actually extracted from a plant or a family of plants that we traditionally associate with the fall, the chrysanthemum. For the garden it is best to use a water-soluble product that you can spray using a hose end sprayer. Before you apply any type of chemical on your plants, make sure they are fully hydrated by watering them well a couple of days before you spray.
Finally, one other way you can attack the problem during the egg stage is by applying a dormant oil to the area in late winter or early spring before the leaves begin to emerge.