Tuesday, July 20, 2010

It's In The Bag!!

This past Christmas, My wife and I finally got to go up to Raleigh and see my mother and her yard. She has been working on it since she bought the house 6 or 7 years ago. It had been about 3 years since we were last there to see it. She comes down to Charleston 3 or 4 times a year and I hook her up with lots of landscape plants. It is nice to work at a nursery. We throw away an untold number of plants for numerous reasons. My mother collects them, gives them some TLC and brings them back to life. This is probably how three quarters of her yard has been landscaped. Anyway, she was excited for us to come up so she could show me the yard and the unusual pine cones on her Leyland Cypress. When we got there, I hated to give her the bad news, they were not pine cones, they were Bagworms! Sometimes the bags ARE mistaken for pine cones or other plant structures. I only bring this up now because I had somebody call me and ask about one on their Citrus tree.....apparently, it was confused.
The cocoons that they spin look something like this:

Photo courtesy of Will Cook

The Bagworm (Thyridopteryx ephemeraeformis) is the larval stage of a moth that is reported to feed on over 100 different plants, I have yet to read about Citrus being one of them though. They prefer juniper, arborvitae, spruce, pine, and cedar but also attack some deciduous trees and shrubs. The first stage larvae feed on the leaf surfaces leaving small areas where the epidermis has been removed. Older larvae consume entire leaves. Late in the Summer, when caterpillars are large and consuming a lot of plant material, branches can begin to appear defoliated. Their distinctive 1.5 to 2 inch long spindle-shaped bags are carefully interwoven using silk and bits of leaves and twigs from the host plant resulting in a well-disguised covering.
Very small caterpillars can spin strands of silk to be carried by the wind, an activity called “ballooning”. Larger larvae may crawl to adjacent plants. They are really rather ugly little critters:

The adult male Bagworm develops into a moth that can fly, but the female remains grub-like and stays inside the bag. Female Bagworms lay between 500-1000 eggs in their bag before they die in the Fall. The eggs overwinter and hatch in May and June. Feeding, growth, and molting continue until August, at which time the mature larvae attach themselves to twigs. They close the bag and reverse themselves so that they are head down in the bag. They remain there for about 4 weeks as pupae.
During September and early October, the female releases a sex attractant pheromone and the males leave their cases and fly to the female bags to mate.

Infestations, which may not be noticed at first, can defoliate trees and shrubs. Heavy infestations over several consecutive years, especially when coupled with other stresses, can lead to plant death. Sadly, this is what was happening to my mothers Leyland.
There are some controls for the Bagworm. If only a few small trees or shrubs are infested, and there are only a few bags hanging, handpicking and destroying attached bags may provide satisfactory control. This must be done during the Fall, Winter or early Spring before the eggs hatch. Make sure you destroy or discard the bags. Eggs in bags thrown on the ground will hatch in the Spring and develop into larvae that could re-infest the plants.
The Bagworm has some natural enemies, such as certain species of birds that are able to tear open the bags and feed on the larvae, in addition to insect predators and parasitoids. Unfortunately, this will not usually control the Bagworm population.
When many small Bagworms are present and feeding, an insecticide may be needed to prevent serious damage. The best time to apply an insecticide is while the larvae are still small (less than 1/2-inch long), usually in early June. Small larvae are more vulnerable to insecticides, and feeding damage is relatively minor. Carefully inspect susceptible landscape plants. Young Bagworms are hard to see at first; look closely for the small, upright bags which have the appearance of tiny ice cream cones made of bits of plant material. There are insecticides labeled for Bagworms. Please read and follow the directions carefully. There are also some systemic controls, (where the plant takes the insecticide up through its vascular system), which makes them well suited to control the Bagworms on tall trees heavily infested in the upper canopy.
There is not much more to say about these things other than.....if they ever become crossed with a feline.....somebody is going to have the let the cat out of the....sorry, that was so bad, I am not even going to finish it!
Happy Growing!

1 comment:

  1. Those moths look like overgrown houseflies! Eww! Anyways, the coloration and patterning on the larvae is actually pretty interesting... not interesting enough to be permitted to live though. They sound awful.