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Showing posts from May, 2015

Watch out for sawflies on pines and roses

Jeffrey Hahn, Extension Entomologist

There are two kinds of sawflies that are active right now, European pine sawfly and roseslug.  European pine sawfly loves pine, especially mugo, red, and Austrian pines.  It has a black head with dark grayish green and light grayish green stripes.  They grow as large as one inch long before they are done feeding.  They chew the old needles of trees and shrubs.  While in many cases, defoliation is not severe, they do have the potential to do extensive damage.

Roseslug is a slug-like translucent greenish larva that grows no more than 1/2 inch long.  They windowpane feed the leaves of roses, i.e. they feed on one layer of leaf tissue between the veins.  Damaged areas are opaque at first but eventually turn brown.  Damage can range from minor to severe.

Both of these sawflies only feed in the spring and are done by June.  If you find these insects on your plants, the first consideration is how large are they.  The closer they are to full grown size, …

Wasp Watchers: Biosurveillance of EAB

Jennifer Schultz, Wasp Watchers Program Coordinator

The University of Minnesota Extension has started a new program called Wasp Watchers that engages citizen scientist volunteers to help detect Emerald Ash Borer infestations throughout Minnesota. With the help of a harmless, native wasp, Cerceris fumipennis, volunteers can conduct biosurveillance for the Emerald Ash (EAB) and help with early detection of this invasive beetle that has destroyed tens of millions of ash trees in over 20 states.

The smoky winged beetle bandit, Cerceris fumipennis is a native, solitary, ground-nesting wasp that specifically hunts beetles like EAB. This harmless wasp is not known to sting people, even when handled. Females forage for beetles in trees and bring them back to underground nests as food for their offspring. This wasp has been used in over a dozen states as a biosurveillance tool for EAB detection. Biosurveillance uses one speci…

High Risk for Oak Wilt

M. Grabowski, UMN Extension

Minnesota is now in the high risk period for new oak wilt infections. This means that the fungus that causes oak wilt, Ceratocystis fagacearum, and the beetles that transmit the pathogen are active. The good news is that oak trees have a natural defense mechanism that is very effective in stopping beetle transmission of the pathogen - bark!

Beetles in the Nitidulidae family are attracted to the sweet fermented smell produced by spore mats of the oak wilt fungus. As they crawl over the spore mat, spores cling to their bodies. Nitidulidae beetles are sap feeding beetles. They are attracted to the sap coming from wounds or pruning cuts on oak trees. As they feed from these fresh wounds, spores from the oak wilt fungus are introduced to the tree's vascular system and disease begins.

A few simple steps will help to protect oaks from beetle transmission of oak wilt. Do not prune oaks during the months of April, May or June. The best time to prune oaks in Min…

Asparagus beetles are active now

Jeffrey Hahn, Extension Entomologist

Asparagus beetles have been sighted in gardens recently.  They can damage asparagus by feeding on the spears and causing browning and scarring.  It can also cause spears to bend over into a shepherd's crook.  If you are growing asparagus, scout your garden now for their presence.  See the Minnesota Extension publication Asparagus beetle in home gardens for information on recognizing asparagus beetles and their best management.

Plant Seeds When the Time is Right

M. Grabowski, UMN Extension

Warm sunny days inspire gardeners to work outdoors. Although everyone is anxious for fresh vegetables from the garden, it is important to be patient and wait for the correct time to plant. Spring soils can be cold and wet. Some vegetables like peas and many leafy greens easily tolerate these conditions and can be planted in the garden as soon as the soil thaws and can be worked.

Members of the cucurbit family, including cucumber, zucchini, summer squash, melon, winter squash, and pumpkin need warmer soils to grow. These plants originate from tropical climates. Other tropical plants like tomato, eggplant and pepper are often started indoors and transplanted to the garden when weather conditions are right. Unfortunately, although cucurbits can be transplanted with care, they have delicate root systems and often do better when direct seeded into the garden. Winter squash and pumpkin seeds can be planted when soils reach 65 F at a 2 inch depth. Zucchini, summe…

Check Spruce Trees for Rhizosphaera Needle Cast

M. Grabowski, UMN Extension

Spring is here and spruce trees are opening their buds and developing young new needles. Now is a critical time to inspect spruce trees for Rhizosphaera needle cast, a common disease of spruce trees in Minnesota.  Rhizosphaera needle cast is caused by the fungus Rhizosphaera kalkhoffii. This fungus infects the young growing needles of Colorado blue spruce, white spruce and Norway spruce. New infections do not have obvious symptoms and many gardeners do not recognize the disease until it is too late to prevent new infections this year.

What to look for
Examine the fully grown needles at the branch tips. These needles were new needles last year and if infected, will be developing symptoms now. Look for discoloration of any kind. Needles should be dark green to blueish green. Needles that look pale yellow green, brown or purplish brown are unhealthy. Use a hand lens to examine the needles. Tiny raised black dots on the needles are suspicious and may be fungal …