Jeffrey Hahn, Asst. Extension Entomologist

Be on the watch for eastern tent caterpillars.  There was a report of these insects at the end of last week in southeast Minnesota and it was reported in the Twin Cities at the beginning of this week.  The caterpillars are bluish black with yellow and a white stripe running the length of the top of its body. They are also mostly smooth except for a series of hairs sticking out along the sides of their bodies. They are two inches long when fully grown. 

However, the first sign you'll notice are the silken tents they create in the forks of branches.  After the caterpillars first hatch, they'll construct this webbing which serves as a shelter they use at night and during rainy weather.  The tent will be small at first but will increase in size and can eventually become quite conspicuous.  During the day they crawl out of these tents and feed on tree leaves.  Although they are found on a variety of hardwood trees, eastern tent caterpillars are particularly fond of fruit trees, including apple, chokecherry, crabapple, plum, and cherry.

Healthy, well-established trees can tolerate eastern tent caterpillar feeding.   Their feeding, as well as the presence of their webs, is just a cosmetic problem and only affects the trees' appearance.  However, young trees, as well as unhealthy, stressed trees, are more susceptible to feeding damage and should be protected.  

Also consider the size of the caterpillars.  As long as they are no more than half their full grown size, i.e. one inch or less, it is worth considering whether to treat them.  This is not an issue now as they are just emerging and they are all small.  However, if an infestation is discovered later, it is important to check to make sure they are not too large (larger than an inch).  The larger they are, the closer they are to being done feeding and then it is not worthwhile to treat them.

A great non-chemical method to deal with eastern tent caterpillars is to wait until they have retreated back to their webbing at the end of the day or on a rainy day and then pull out the webbing, along with the caterpillars.  Then bury or bag them to properly dispose of them (you could burn them if it is permitted where you live).

There are a variety of residual insecticides that you can use if it is desirable to protect your trees.  Consider using products that have a low impact on the environment, such as Bacillus thuringiensis, spinosad, and insecticidal soap.  Bacillus thuringiensis is a particularly good product if the tree is flowering since it will not harm visiting honey bees.  If you use insecticidal soap, the product needs to directly contact the insects.  There is no residual activity so you may need to repeat the treatment.

Jeffrey Hahn, Asst. Extension Entomologist

We have endured a long cold spring but now the weather is finally getting warmer so it is enjoyable to be outside again.  Finally, we are ready to enjoy our favorite outdoor activities.  You definitely want to get outside but with the return of nice weather also come ticks.  Take the proper precautions and protect yourself from these pests.

The two most common ticks in Minnesota are American dog ticks (also called wood ticks) and blacklegged ticks (formerly called deer ticks).  While American dog ticks are not important vectors of disease in Minnesota, they are nuisances because they bite us (also dogs too!).  Blacklegged ticks are also nuisances but they can be potentially more serious as they transmit diseases, including Lyme disease, anaplasmosis, babesosis, and Powassan encephalitis to people in Minnesota.  Of these, Lyme disease is the most common.

You are most likely going to encounter ticks in tall, grassy areas and in the undergrowth of hardwood forests so avoid those areas when possible.  When you are out in areas where ticks are known to occur, one of the best methods of protecting yourself is the use of a repellent.  You can apply DEET to both skin and clothes, while products containing permethrin should only be applied to clothes.  It is also very important to check yourself for ticks after coming back inside.  The sooner, you can find any ticks that may have crawled onto you, the sooner you can remove them, hopefully before they have started to bite you.  Ticks can't transmit disease if they are not biting.

For more information, see Ticks and their Control and Tick-borne diseases in Minnesota.

As gardeners inspect their landscapes this spring, many trees and shrubs have been found with extensive rabbit damage. Rabbits are one of the most commonly seen mammals in the urban environment. In Minnesota, our most common rabbit is the Eastern cottontail, Sylvilagus floridans.

Rabbits will spend much of their time eating grasses and other herbs but they will also chew on the bark of trees and shrubs and eat the buds of shrubs in the winter and spring. If left unprotected, rabbits will sometimes eat the bark from around the base of a tree or shrub. This is called "girdling" and can kill the plant.

Read Rabbits and Trees and Shrubs by wildlife expert Jennifer Menken of the Bell Museum to learn more about protecting landscape plants from rabbit damage.

Michelle Grabowski, UMN Extension Educator

Persistent cold weather and late snow fall mixed with freezing rain have created ideal conditions for the growth of snow molds this year. Snow molds are caused by fungal pathogens that thrive in cold temperatures (just above freezing to about 60F) and high humidity.

Two types of snow mold are common in Minnesota. Pink snow mold, caused by the fungus Microdochium nivale, results in round dead patches in lawns that can be an inch or two across or as large as a dinner plate. These dead patches are often pale tan in color, matted down and may have a dark brown border. In sunlight pink snow mold patches turn pink to salmon colored as the fungus produces spores of these colors.

Gray snow mold, caused by several species of Typhula, also cause pale gray to tan patches of matted down brittle grass that can spread up to 3 feet across. If the matted down grass of gray snow mold is examined closely, gardeners can see small black dots, about the size of a pen tip. These black dots are sclerotia, resting structures produced by the fungus that allow it to survive through harsh conditions. It is not uncommon to find both pink and gray snow mold in the same lawn.

The good news is that although snow molds thrive in cold wet conditions, they go dormant as the weather becomes warm and dry. In many cases the snow mold fungi blight the grass leaves but do not kill the crown. In these situations, the grass will recover as the fungal pathogen goes dormant. In severe cases of snow mold, the grass plant may die and gardeners will need to reseed the infected area.

For now there are a few things that gardeners can do to speed the fungal pathogen into dormancy. Remove or spread out any remaining snow piles, so the snow melts quickly and the grass below is exposed to sun and air. Rake the lawn to remove any leaf debris and to fluff up matted down patches of turf. This will help improve air movement around the grass plants so leaves dry quickly after dew or rain. A light application of fertilizer in the infected patch can help grass recover. If no recovery is seen, reseed the area, taking care to rake away matted down grass so that seed has good contact with the soil below. Fungicides are not effective in controlling snow mold once the disease is established and should not be used at this time of year.

Jeffrey Hahn, Asst. Extension Entomologist

The following is from a news release that was issued on May 2, 2013

The United States Department of Agriculture (USDA) and the U.S. Environmental Protection Agency (EPA) released a comprehensive report last week on honey bee health. The report states that there are multiple factors playing a role in honey bee colony declines, including parasites and disease, genetics, poor nutrition and pesticide exposure.

In October 2012, a National Stakeholders Conference on Honey Bee Health, led by federal researchers and managers, along with Pennsylvania State University, was convened to synthesize the current state of knowledge regarding the primary factors that scientists believe have the greatest impact on managed bee health.

Key findings include:

Parasites and Disease Present Risks to Honey Bees:
• The parasitic Varroa mite is recognized as the major factor underlying colony loss in the U.S. and other countries. There is widespread resistance to the chemicals beekeepers use to control mites within the hive. New virus species have been found in the U.S. and several of these have been associated with Colony Collapse Disorder (CCD).

Increased Genetic Diversity is Needed:
• U.S. honeybee colonies need increased genetic diversity. Genetic variation improves bees thermoregulation (the ability to keep body temperature steady even if the surrounding environment is different), disease resistance and worker productivity.
• Honey bee breeding should emphasize traits such as hygienic behavior that confer improved resistance to Varroa mites and diseases (such as American foulbrood). 

Poor Nutrition Among Honey Bee Colonies:
• Nutrition has a major impact on individual bee and colony longevity. A nutrition-poor diet can make bees more susceptible to harm from disease and parasites. Bees need better forage and a variety of plants to support colony health.
• Federal and state partners should consider actions affecting land management to maximize available nutritional forage to promote and enhance good bee health and to protect bees by keeping them away from pesticide-treated fields.

There is a Need for Improved Collaboration and Information Sharing:
• Best Management Practices associated with bees and pesticide use, exist, but are not widely or systematically followed by members of the crop-producing industry. There is a need for informed and coordinated communication between growers and beekeepers and effective collaboration between stakeholders on practices to protect bees from pesticides.
• Beekeepers emphasized the need for accurate and timely bee kill incident reporting, monitoring, and enforcement.

Additional Research is Needed to Determine Risks Presented by Pesticides:
• The most pressing pesticide research questions relate to determining actual pesticide exposures and effects of pesticides to bees in the field and the potential for impacts on bee health and productivity of whole honey bee colonies.

Those involved in developing the report include USDA's Office of Pest Management Policy (OPMP), National Institute of Food and Agriculture (NIFA), Agricultural Research Services (ARS), Animal and Plant Health Inspection Service (APHIS), Natural Resource Conservation Service (NRCS) as well as the EPA and Pennsylvania State University. The report will provide important input to the Colony Collapse Disorder Steering Committee, led by the USDA, EPA and the National Agricultural Statistics Service (NASS).

An estimated one-third of all food and beverages are made possible by pollination, mainly by honey bees. In the United States, pollination contributes to crop production worth $20-30 billion in agricultural production annually. A decline in managed bee colonies puts great pressure on the sectors of agriculture reliant on commercial pollination services. This is evident from reports of shortages of bees available for the pollination of many crops.

The Colony Collapse Steering Committee was formed in response to a sudden and widespread disappearance of adult honey bees from beehives, which first occurred in 2006. The Committee will consider the report's recommendations and update the CCD Action Plan which will outline major priorities to be addressed in the next 5-10 years and serve as a reference document for policy makers, legislators and the public and will help coordinate the federal strategy in response to honey bee losses.

To view the report, which represents the consensus of the scientific community studying honey bees, please visit: http://www.usda.gov/documents/ReportHoneyBeeHealth.pdf

Jeffrey Hahn, Asst. Extension Entomologist

Small, fly-like insects have been appearing in people's homes this spring, especially around windows.  Although they look like gnats or flies (one person thought they looked like fleas), these insects are hackberry psyllids.  Despite their similarity to flies, these insects are more closely related to aphids and leafhoppers (they actually look like tiny cicadas).

Psyllids are about 1/8 inch long with a somewhat compact body.  Their wings, a mottled brown with small black and white spots, fold up tent-like over their backs.  During the spring and summer, they are associated with hackberry trees where they are gall producers on leaves.  Adults emerge from their galls in the fall.  Soon after that, they seek shelter to protect themselves from the winter; many end up in homes and other buildings, similar to boxelder bugs and lady beetles.

After they move into various cracks and spaces around the exterior of homes, psyllids remain dormant during the winter.  As warm weather arrives in the spring, many of them become trapped inside homes as they become active (they can also emerge inside buildings during mild winter days).  Fortunately, they do not live long indoors.  They also do not reproduce inside buildings; the individuals you see in the spring have been inside your home since fall.  They are harmless and just a nuisance. 

When you see psyllids in the spring, the only necessary control is physical removal.  Eventually they will either die inside or find a way to get outside.  In either case, this problem will be over this soon.  For more information about psyllids, including steps you can take in the fall to help prevent their entry into your home, see our publication on hackberry psyllids.  

Karl Foord - Extension Educator, Horticulture

Removing straw mulch on strawberries using lilac buds as an indicator

Sometimes nature is a better indicator of the best time to take action than our measuring equipment. Researchers Terry Nennich and Dave Wildung attempted to determine the best time to remove the straw mulch on strawberries using growing degree days (GDD) which are a measure of heat accumulation. GDD are often used to predict when a plant might flower, or how developed a pest might be to optimize the timing of control.

In this case Terry and Dave found complications that made GDD a less reliable indicator for the timing of mulch removal. Given this they looked for other signs in nature that might be more useful. Their conclusion was that when the lilac buds open, it is time to take off the straw. This correlated well with the end of strawberry dormancy. Timing is critical as a delay in removal was shown to reduce both the total yield and the size of berries. The longer the delay the greater the loss in yield.

To this end please observe the pictures of bud break in common lilac (Syringa vulgaris) in photo 1 and in dwarf Korean lilac (Syringa meyeri 'Palibin' in photo2. Both taken May 6, 2013 in Chaska, MN.

Is it time to remove the straw mulch from your strawberries? What is the status of the lilac buds in your neighborhood?