July 9, 2013

Meadow Spittle Bugs

There are literally thousands of things that surround us on a daily basis that we walk past without a second glance (or often even a first one).  However, if something is brought to our attention, we tend to notice them over and over, even if we’ve never seen them before.

Many insect and diseases are like that.  One afternoon last week, I got an email from someone asking if I knew if people were noticing a particular pest in their strawberries.  It is a very minor pest, which I’d heard of but had never set eyes on before.  Imagine my surprise (and delight, I will admit to it) when the very next morning, as I was weeding my flower bed, I came across this very insect.  Within an hour, I found it again and again in my strawberries.  It makes picking strawberries that much more interesting, since I am “eager” (yeah, I’ll admit to that), in a weird way, to find this little critter again.
Spittle mass on Creeping Bellflower (weed)
So, let me share with you this little insect that is the “proud” possessor of a fairly disgusting reputation but is, in fact, pretty fascinating.  The insect that I am referring to is the Meadow Spittle Bug.

The Meadow Spittle Bug (Philaenus spumarius) is found a number of different host plants, such as strawberry, clover, alfalfa, a number of grasses, various weeds and some ornamental plant species and is generally considered to be a minor nuisance pest in Alberta.  It is lists about 400 plant species as hosts and is considered to be a general feeder.  It can be damaging in some regions and on some crops, but not on the Canadian Prairies.

Most likely you’ll find (and recognize) MSB more by touch than sight most of the time and, odds are, MSB will be there but you won’t see it.
Frothy spittle "gift"
The first (and predominant) sign of spittle bugs is a subtle-ish frothy or foam mass on the stems, leaves, or perhaps the fruit of the host plant.  Spittle masses can range in size, but are often upwards of ½ an inch or more in diameter.  In my experience, masses can be found pretty much anywhere in the plant canopy but are most often in the lower parts of the canopy.  As you move strawberry leaves aside to find and pick the fruit, you’ll get a wet/slimy feeling and find your fingers with a bit of wetness or foam on them.  Not overly pleasant, but bearable.  You might also catch a glimpse of a mass on an upper leaf surface.
Spittle mass on upper leaf surface of a strawberry
Closer view of spittle bug mass - note individual bubbles
Spittle bugs feed by piercing and sucking.  MSBs don’t tend to cause yellowing, but if there are lots and lots of spittle bugs on the plant, you might see some stunting or perhaps wilting of the plant.

MSBs look a bit like large aphids (a bit egg or pear-shaped), but adults are mottled and winged and can hop and fly (aphids just sort of mosey slowly or park, for the most part).  They are approximately 7 mm in length.  The nymphs are what you will find inside the spittle mass.  They range from orange-yellow to green (depending on the instar (growth stage)) and can stay inside the masses for up to a month while they mature.  Unlike aphids, they can really move when they are motivated.

Spittle bug nymph (probably later instar)

Spittle bug nymph (side view)
MSBs overwinter as egg masses that are laid on lower plant parts.  Nymphs hatch and emerge in late spring.  Once the nymphs hatch they start feeding and produce a frothy mass of little bubbles.  After close examination, I can safely say that they essentially blow the bubbles out of their nether regions, which extends to look a little like a short elephant trunk that waves back and forth, side to side, depositing a bubble one at a time.  In a short time (2-3 minutes), they can produce enough bubbles to equal half their body size.  The spittle masses protect the MSB nymphs from predators and desiccation.
Meadow Spittle Bug nymph - note the slightly distended rear end (where the bubbles come from)
Spittle bug nymph blowing bubbles out of its nether regions
Some sources lead me to believe that spittle bugs are more of an issue in humid regions, which would suggest that MSB might be more of an issue in more humid years.  It certainly jives with the tendency of the MSBs to put their spittle masses in the lower canopy, where the humidity is higher.

While the MSB is gross (people hate to put a hand in the masses), it generally doesn’t merit any sort of control measures.  Weedy areas/fields tend to have more MSBs, so controlling weeds can cut down on hosts and keep populations to a minimum.  Chemical applications (if they are made) for other pests may coincidentally control the MSB, however the spittle masses also protect the nymphs for the most part.

While I am not an “insect guy”, you have to admit that insects can be pretty interesting.  So, keep an eye open.

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