What is it with lavender and spittlebugs? Every year as the flowerheads are forming the spittlebugs arrive. They definitely seem to prefer Lavandula angustifolia to Lavandula stoechas (the one with the bunny ears) and certainly can be found on many other plants but around here L. angustifolia seems to be their favorite haunt.
Your spittlebug may not be my spittlebug given there are about 2500 species of insect that make those delightful bubbly houses. Spittlebugs are related to aphids and like their cousins, they are sap suckers. They rarely do plants much harm although sometimes you’ll see twisted and deformed leaves.
Eggs laid in the fall hatch in the spring into an immature form, the “spit” forming nymphs. The nymphs are soft-bodied, wingless and apparently amazingly good jumpers (2′ – better than a flea). Wipe or hose off the spittle and take a look. I have but I’ve never seen one jump. The spittlebug nymphs feed on the plants (they suck juice out of the xylem, the water conducting cells, usually sap suckers go after the nutrient dense phloem), transform the excess internally into the substance that can hold air bubbles so well, inject the substance with air and excrete it through their anus (possibly they excrete first and eject afterwards, probably more comfortable that way). Clearly, “spittle”bug is a misnomer but alternative and more accurate terms sound significantly worse. By summer the nymphs have become spittle-free but still sap sucking adults that rarely get noticed.
The purpose of the spittle-like substance is likely protection of some sort. It could be a hiding place although any insect with a brain would say, large globules of spit means a tasty nymph within. It could also be that the coating prevents the nymphs from drying out.
WHAT TO DO ABOUT SPITTLEBUGS
Spittlebugs can be unsightly but do little harm to plants. It’s definitely not worth using insecticides on them. You are usually told to hose them off. I find that they aren’t that easy to hose off of tender herbaceous plants. Just how strong of a spray am I supposed to use to get those guys off? If there aren’t many I just manually remove them. If there are a lot I try the hosing and then go back and check and remove some of the ones that I missed/can’t get to easily.
Spittlebugs were the bug of the month in June 1996 – they’re not on a calendar but in the Sarabogram. If you want to read more about spittlebugs, check it out here.
Also, watch this video and see if you can figure out, “Do spittlebugs inject air before or after the spit substance leaves their body?”