Maggie......those are Pine sawflies caterpillars. They love Mugos as well as others. See topic "Caterpillars on pines" on May 04, 08. Other forum members chimed in on that thread.

We had a bad infestation of those critters on our Austrian pine a couple years ago. It was creepy...if I approached the tree, they all would stand up and sway in unison.

I put on gloves, grabbed hand-pruners and a big black plastic garbage bag, and pruned off the infested branches at the trunk. I was very slow and methodical while I did it, because I didn't want any of the beasties to fall onto other branches.

I had to cut off several branches (and I sprayed the rest of the tree with Sevin--Sevin is harsh, I know, but these were three eight-foot, Austrian pines...and those larvae can strip one bare in a matter of days...so it was survival of the trees over survival of the worms...

I didn't see any more after cutting off the infestations. The tree had a couple of bare spots from the pruning, but that was far preferable to me than complete pine death and removal. It's amazing what those little larvae can eat!

Good luck!

Technically, pine sawfly larvae are not caterpillars. As to control, any general purpose insecticide will easily control them. If you don't like chemies, you can disrupt their feeding by blasting them with high-pressure water from your garden hose/nozzle. Doing this a few days in a row will pretty much end the problem. Also, if you catch them early enough, before they've attained much size, insecticidal soap will get em.

+oM

Or simply put on an old pair of gloves, and run each infested shoot through your hands.

Another good option is to hang a very visible bird feeder in the tree; this will attract a lot of birds, and the ones waiting their turn in the queue will feast on the insects.

Resin

Hey, anyone know if those things also get on fruit trees? I could swear they are the same things I am seeing on my apple & pear trees. YUK!

Well, pine sawfly larvae certainly don't feed on fruit trees. Perhaps you are seeing tent caterpillars. They love fruit trees. Or, it could be the larval stage of some other sawfly. But no, not pine sawfly.

+oM

A mixture of 16 oz, 70% rubbing alcohol, 16 oz water and a couple of tablespoons of Ivory or Dove dish soap will kill them. Put the mixture into a trigger spray bottle and spray away. I used this mixture on them a couple of years ago and they die within a minute or so. It is a contact poison so you must spray them to kill them. Don't use Dawn or any other "detergent" as this may damage the plant.
Good luck,
Mike
tl³
p.s. I finally removed the Pinus mugo 'Big Tuna' because they attacked the plant every year. I have not had them attack any of my other mugo pines and they were very close to the 'Big Tuna'.

Hi Mike,

This is why you never got rid of them.

There are two to three generations/year. The pine sawfly overwinters in the prepupal stage in its cocoon spun in the litter of the soil beneath the infested trees. Pupation occurs soon after the onset of spring warm weather, and adults emerge in a few weeks. Eggs deposited in the needles hatch in three to five weeks. Larvae feed gregariously on new and old needles and also on the tender bark of young twigs. Larvae begin spinning cocoons in late June or early July. Second generation adults emerge in July and August. Larvae feed through September and then spin their cocoons. In warmer areas, adults will emerge at the end of September to late October and lay eggs for a third generation that remains active into December.

Dave

Thanks, Dave, that's good to know. There was a Pinus nigra a couple of blocks from me that was completely cleared of all of the tree's older needles. They didn't touch the new growth, however, on either my mugo pine or the Pinus nigra. Weird.
Thanks,
Mike
tl³