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Jumping oak gall

Would you believe it if you saw thousands of pinhead-sized yellow balls falling from oak leaves to the ground and then repeatedly jumping, rather than bouncing off the ground? Believe it or not, the jumping of these leaf galls is caused by the activity of tiny wasp larvae inside the galls, just like miniature Mexican jumping beans. This insect is known as the jumping oak gall wasp, Neuroterus saltatorius. Larvae have chemicals in their saliva that stimulate the oak leaf tissue to form the yellow blister-shaped galls. As the galls mature, they are released from the leaf and rain down onto the soil. The galls bounce around until they become lodged in the soil and they overwinter there.

At times, these galls can become so numerous that they cause discoloration of the oak leaves and even premature loss of leaves. Yet, they do not affect the health or vigor of infested trees. Only expect jumping oak galls to be found for a year or two in any location, so be sure to enjoy these marvels when you find them.

Rhizosphaera needle cast

One of the common calls from homeowners this season has been "My spruce tree is dying." Upon asking the caller if it is a blue spruce, the answer is almost always yes. One of the most common diseases of ornamental spruce in Minnesota is Rhizosphaera needle cast, Rhizosphaera kalkhoffi. Colorado blue spruce is usually the recipient of this fungal disease; however white and even Norway spruce can be affected. Signs and symptoms that indicate a Rhizosphaera infection are fungal fruiting bodies and current years' needles that look green and healthy while older needles are purple-brown or missing. Use a hand lens to find minute, black fruiting bodies erupting out of the needle stomata.

The loss of needles from the inner branches on the lower crown gives it a hollow appearance. Repeated infections over several years may cause these lower branches to die. At this point the tree has lost its appeal as an ornamental. The extent of the infection varies, depending on environmental factors that favor the spread of the spores, susceptibility of the tree, stress and number of years of infection. Unless the branch is dead you will have the current year's needles and last year's needles (already infected).

High moisture levels and poor air circulation favor the spread of this disease. Infection of new needles occurs in the spring when spores are released from the fruiting bodies of infected needles. These spores splash or are wind blown onto uninfected needles, where under favorable conditions, they germinate and invade the needle.

Treatment requires the use of a preventative fungicide called chlorothalonil. It is sold over the counter under such names as Ortho Multipurpose Fungicide, Daconil 2787, Ferti-lome Fungicide and others. It should be applied when the new needles are half elongated, approximately late May/early June and a second application a month later. Severe infections may take several years of treatment. It is important to note that the lost needles do not return. You are protecting future growth only. Planting trees resistant to this disease, maintaining proper soil and water conditions, mulching and providing adequate air circulation are important factors in controlling this disease.