The Beak of Death--Pest Control Via Bluebird
I was afraid that this post would end up being about just the pest, so I'm thrilled to tell you that my little pine tree has survived the onslaught due to physical intervention and the gastronomic inclinations of our neighborhood bluebirds.
So let me introduce you-- to the Red Headed Pine Sawfly... or at least its larvae.
May it rest in peace.
This cluster of caterpillar-like-thingees is not caterpillars. Not being a gifted entomologist, I of course turned to Google for some identification tips. The lovely thing about Google is that you really can type in something like "caterpillar devouring pine tree" and get real answers. With pictures. The references I found set me straight very quickly as to the nature of my pest, though the descriptions on most of the sites were not particularly accurate, even with the photos right there! Fortunately, I was able to make the ID from the images, as opposed to the faulty descriptions of my non-caterpillars.
Red Headed Pine Sawflies are native to North America (at least it's native!) and prefer to munch down on the two- and three-needle pines, such as Virginia Pine, Loblolly, Slash, Longleaf, Jack, Red, Mugo and Shortleaf pine. It will occasionally use white pine. Mugo is not a native (brought from Europe in the late 1700's), but I include it in this list because it is a frequent landscape choice for those seeking small-scale evergreens. These pictures show the sawfly larvae in a Mugo pine.
The Red Headed Sawfly (Neodiprion licontei), as an adult, has an obviously red head and thorax (excellent, if small, picture on the PA site). It has a black abdomen, and lays eggs in the needles of its chosen host plant. We never saw the newly-hatched larvae. But once the naked candles appeared on our little pine (sawflies usually prefer 15' or smaller trees), we found the clusters of more mature ones. More pictures here at BugGuide.
When the smaller larvae hatch out, they eat the outer portion of the needles, leaving a straw-like brown twisty hair-like thing that looks like it either just got out of bed or needs a new conditioner. The larger larvae just chow down on the whole thing. When you get close to them, these guys will stand up and wave at you in their "come any closer and I will spit on you!" posture... it's pretty funny when they start doing it all over the whole plant. It's either a threat or they've decided you are their new god.
As you can see in the image, these guys are pale whitish-yellow, but as with most things, variation does occur. They can make it all the way to nearly green from the basic yellow. Their spot patterns may also vary. The heads are red-orange, as you see here, and they have a larger black spot on their tail end that masquerades as a head. Many of the early sites I checked referred to three rows of black spots, but what they must have MEANT to say was three rows on each side of the back. The bottom row is directly above the prolegs.
And this was my new thing of the day--CATERPILLARS have up to only five sets of prolegs. If you don't believe me, google "monarch caterpillar" and count the little stubbs in those pictures. Sawfly larvae, on the other hand, have more. From the picture at left, I am certain of 7 pairs--it might be eight. The better to hold their needles with, I reckon.
Sawfly larvae will eventually drop to the duff or soil beneath the host tree to spin a cocoon, and will overwinter in a prepupae state, finally pupating and hatching out after the weather warms. The cocoon stage is where a damaged plant may get its revenge--chemical signals sent by the plant can draw predator or parasite insects, such as wasps, that will lay their eggs into the cocoon, thwarting the second wave of the pest before it can emerge to defoliate another swath of pine. For more on the ways plant protect themselves, go here.
So our story might have ended there had we no access to predators in this yard. But we do. We have scores of songbirds who are insect specialists. In fact, we have a nesting pair of bluebirds making use of a house in the front yard, and they have a bunch of hungry babies. Knowing this, I decided to take a chance. I picked off a large quantity of the sawfly larvae and laid them in a heap on the flagstone path running beside the birdhouse and then went inside.
The first thing I had to do was get the sticky off my hands--these guys exude pine pitch! Soap was no good by itself, so I resorted to Goo Gone, which destroyed the sticky with no problem. Then I made a dash for the bedroom window which looks out on this particular birdhouse. Imagine my delight to see not one, but BOTH parents scooping up the non-caterpillars!
I have no way of knowing whether they had already been working over the mature larvae on the Mugo pine. They were obviously no strangers to these guys, taking them up and off--beating them on the pavement, it looked like--and returning to the nest box to present dinner to their noisy offspring.
Later, when I was trying to get these photos, mom showed up (photo above) with a mouthful that definitely had not come from the Mugo (as I had been sitting in position for quite awhile). When you increase the size of the photo, it's not clear exactly what she has, but it is certainly in the realm of possibility that she has another larvae of the same ilk in her beak. There are several white pines in adjoining properties in the neighborhood, so plenty of habitat for sawflies is available.
As I write this, I have not been able to locate a single new sawfly larvae on our little Mugo pine. The bedraggled-looking parents continue to find things to shove down the throats of their young, however.
From the PA site:
"Control: Natural enemies, such as rodents, birds, and predaceous and parasitic insects, play an important role in reducing sawfly populations."
This is how the system is supposed to work. "Pests" feed other insects, or other critters like birds. No pests, no baby bluebirds.
Don't need no stinkin' pesticides. I've got bluebirds.