Rhizosphaera Needlecast

Rhizosphaera Needlecast

What is it?

Rhizosphaera Needlecast, or Rhizosphaera kalkhoffii, is a fungus that affects spruce trees, most commonly Colorado blue spruce. It usually doesn't kill tree, however it does make them look sick. This is particularly devastating to tree nurseries or Christmas tree farms.

What does it do?

A spruce tree that has no issues will normally keep its needles for around 6 years. When one becomes infected with Rhizosphaera Needlecast, however, it may only hold the infected needles for one year. As with other diseases of conifers, the fungus starts at the bottom of the tree and works its way up. The reason this happens is because the ground under the tree is more susceptible to growing and sheltering diseases than the tree itself. 

It starts off by infecting the new needles in May or June, however it usually will not be noticeable until spring the following year. This is when the needles on the lower branches get a somewhat purplish hue to them (see above picture), then die off and start dropping. The spring rain then splashes the infection onto healthy needles, which restarts the cycle. This can sometimes kill the lower branches of the tree.

Do you have it?

Your first hint at a Rhizosphaera Needlecast infection will be when you see needles that appear to be purple when the sun hits them. The best way to find out for sure if your trees have it is to look at the infected needles under a magnifying glass. If they have hairy looking black spots on them, then there's a pretty good chance you found your disease. These black spots are actually the breeding grounds of the fungus, waiting for the rain to take them somewhere else on the tree. Here's what it will look like:

Photo credit: ohioline.osu.edu/hyg-fact/3000/3059.html

How to manage it:

As always, the best form of control is to know the disease before you buy a tree that might have it. If it's already in your yard, you're going to have to do a little more than that.

• If you have several spruce in your yard and only one of them is infected, make sure that you trim that tree last. The disease can be transmitted to the healthy trees just from the clippers. If you must trim your infected tree, be sure to trim that one last. Afterwards, sterilize your tools in a bucket of denatured alcohol for about 5 minutes.
• Try to keep the tree as healthy as possible. This includes vertical mulching, irrigation and aeration.
• Chemical: Since  Rhizosphaera Needlecast is a fungus, an applied fungicide could do wonders for your tree. Brands such as Daconil 2787 and Bravo might just do the trick for you. If you are goping to do it yourself, make sure to read all of the warnings and instructions. 
• Or you could always call your local tree care specialists.

Evergreen Bagworm

The Evergreen Bagworm is a pest found in almost all of the US, as far west as Nebraska, North to New England, and South to the Gulf of Mexico. Although it's called the Evergreen Bagworm, it doesn't necessarily attack only evergreens. It attacks cypress, pine, juniper, spruce, locust, birch, black locust, apple, oak, willow, sycamore, poplar, maple, and several other species of plants and trees. Red Cedar and Arborvitae are their favorite food, and are attacked most often. In my career I've seen them on just about everything, from a metal stop sign to a plastic eves trough. They can wiggle themselves anywhere, but they only feed on plant material.

They start life out as a black larva, growing brown and tan as they mature. Inside the mothers empty sac from the previous season, up to 1000 eggs can be hatched. They hatch between early April and June, depending on the weather and the temperatures. When they hatch, they drop down from the mothers sac on a small piece of silk string, which usually gets caught by the wind, carrying the larvae to their host tree. Once they reach their new host, they immediately start forming their own case to live in, feeding off the tree and using its leaves to build its sac. It wraps its' silk around the branches of the tree, sometimes so tightly that it can hurt the tree just from the squeeze.

These are some pictures of bagworms that I found just today. They were on an arborvitae.

Adult males come out of their sac around late August, and look like a black moth with a 1 inch wingspan. The females, however, never leave their sac. They die in it, surrounded by the eggs that will be hatched in the next season.

The sac that you may see hanging off of your trees is made of silk, fecal matter, and pieces of the tree that the Bagworm is latched onto. Often times that sac is hard to spot to the untrained eye. Especially on spruces, they look just like pine cones and blend in very well. The camouflage tactics that the Bagworm uses is very effective in keeping away predators.





Ways to stop Bagworms from destroying your trees: 
If you find that you have bagworms, one of the simple solutions is to simply pull them off the braches you find them on. It's best to do this right before spring, as the female is already dead and the eggs haven't hatched yet. Make sure to throw them away in a sealed container, so that the hatching eggs have nowhere to go. Another option: fire. Burn the sacs as you pick them off.

The chemical solution is insecticides, and they should be sprayed mid to late June. Bagworm feeding slows in August, which means insecticides won't be as effective during late summer/fall. Make sure to cover the entire tree with the insecticides because you usually will not be able to see all of them. New larva are very small and hard to spot.