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Extension > Yard and Garden News > 2017

Thursday, September 21, 2017

Ground beetles are only nuisances

Jeffrey Hahn, Extension Entomologist

Some residents have been finding ground beetles in their homes lately. Ground beetles are a common group of beetles that are usually medium sized and dark-colored. As their name suggests, they are typically found on the ground where they hunt other insects. Because of their predaceous activities, they are considered to be very beneficial.
Ground beetles captured in a stick trap.  Ground beetles are
just nuisance and should be tolerated when possible.  Photo:
Jeff Hahn, University of Minnesota Extension

Occasionally in August and September, ground beetles can be found entering homes. Fortunately they are harmless to people and do no damage to property. Some people mistake them for cockroaches which is an insect that can infest homes so it is important to correctly identify any insects that are found. Ground beetles are short-lived and do not reproduce indoors.

Tolerate ground beetles when found in homes as much as possible. The only necessary control is physical removal, especially when only a few are seen. An option for controlling ground beetles is the use of sticky traps. Set out the traps in areas where ground beetles are being found; it is then an easy matter to remove the traps when they have captured ground beetles.

Regardless of what is done, ground beetles are a temporary problem that will go away on their own by the time the weather starts to cool off.

For more information, see Ground beetles in homes.

Monday, September 11, 2017

Late summer butterfly explosion

Photo: Britt Forsberg
Elaine Evans, Extension Educator

If you have been spending time in your flower gardens recently, you may have noticed many brown and orange butterflies visiting plants to drink nectar. Adults of the Painted Lady butterfly, Vanessa cardui, are gathering at flowers in unusually large numbers to prepare themselves for migration down to the southwestern U.S. and northern Mexico. The Painted Lady butterfly is one of the most widely distributed of all butterfly species, but is not frequently seen in Minnesota most years. According to Chip Taylor, director of Monarch Watch at the University of Kansas, this is probably the largest migration he has seen in over 30 years (LJWorld.com September 8, 2017). These larger migrations often follow rainy periods in their wintering grounds. 

You can help these butterflies on their journey south by making sure that you have flowers to provide them with the nectar they need to fuel their long journey and keeping these flowers free of pesticides. According to butterfliesandmoths.org these butterflies prefer nectar from composites 3-6 feet high, especially thistles; also aster, cosmos, blazing star, ironweed, joe-pye weed, red clover, and milkweeds. Many of these plants can also serve as food for the caterpillars if the adults make it this far north again next year. Unlike monarch caterpillars, which require milkweed, the painted lady caterpillars have been found on over 100 different host plants, but favorites include thistles and legumes.
Photo: Britt Forsberg

If you have not already seen them, a visit to a pollinator garden planted with a variety of blooming flowers is likely to reward you with a stunning showcase of insect beauty.

Here are a few links with more information about Painted Ladies.

Friday, September 8, 2017

Late blight takes out tomatoes

M. Grabowski, UMN Extension Educator
Late blight symptoms on tomato leaves.
M. Grabowski, UMN Extension 


After carefully cultivating tomato plants throughout the summer, many Minnesota gardeners have been shocked to see their plants devastated by blight and fruit rot in a matter of days. The culprit is late blight, a disease of potato and tomato plants. Late blight does not cause significant damage every year in Minnesota but prolonged cool wet weather this year has created ideal conditions for disease.

Late blight is cause by the pathogen Phytophthora infestans, a fungus like organism that thrives in wet conditions. The scientific name of the pathogen translates to ‘plant destroyer’ and the pathogen lives up to its name.  Late blight is the plant disease that ruined the potato crop in the infamous Irish potato famine of the 1840’s and the disease has been responsible for numerous epidemics since then.

How to identify late blight
  • Leaves have large, dark brown blotches with a green gray edge.
  • Stem infections are firm and dark brown.
  • Disease progresses very rapidly in cool wet weather and the entire plant may turn brown and collapse in just a few days.
  • Fruit have firm dark brown blotches. If the tomato is cut open, dry brown rot can be seen extending into the fruit. Fruit only become soft and mushy when bacteria invade after the initial infection.
  • In high humidity, thin powdery white fungal growth appears on infected leaves, fruit, and stems.

Late blight on tomato fruit. Mold appears in high humidity.
M. Grabowski, UMN Extension 
Management options for home gardeners
Once late blight has been found in a garden, there is little that can be done to help the plant. The disease simply moves too quickly. Harvest any tomatoes that are not showing symptoms and keep them in a well ventilated area to ripen. It is likely that a few are infected but not showing symptoms at the time of harvest, so check on tomatoes regularly and discard any infected fruit. Potatoes from infected plants should be dug up as soon as possible. Uninfected tubers can be eaten but should be checked regularly for rot during storage. Discard infected tomato fruit and potato tubers along with infected plants.

Infected plants should be removed or destroyed as soon as possible to prevent the thousands of airborne spores forming on the leaves from spreading to neighboring plants.
  • Infected plants can be placed in a plastic bag or under a plastic tarp and left to cook in the sun for several days. Once all of the plant material is killed, the plant can be composted or buried.
  • Plants can also be shallowly buried in soil, as the freezing winter temperatures will kill both the plant and pathogen.
  • Infected plants can be placed in a compost pile that completely heats up and breaks down all plant material. Do not use a compost piles that does not thoroughly heat up or completely break down plant material. These mildly warm piles can sheltered infected plant material from the freezing cold and allow the late blight pathogen to survive from one season to the next. If you are unsure how hot your compost pile gets, heat infected plant material in a plastic bag before placing it on a compost pile.   

Can fungicides help?
Fungicides are not effective once a plant has become infected with late blight. For many gardeners, it is too late to apply fungicides. Fungicides only work to protect healthy plants and prevent new infections. Gardeners that have not yet seen late blight may choose to protect their tomato or potato crops with a fungicide that has copper as the active ingredient. The product MUST list tomato and/or potato on the label and the gardener MUST follow all label instructions to use the pesticide safely. There are a number of copper fungicides registered for use in home gardens. Some are certified for organic use.

Will late blight come back next year?
The late blight pathogen can only survive Minnesota’s winter if sheltered from extreme cold in infected plant material. This typically only occurs in large piles of unmarketable potatoes that are sometimes left on field edges or in infected potatoes that are buried deep enough to survive the winter. Most years the late blight pathogen must be brought into the state on infected potato seed, infected tomato transplants, or as windblown spores from other areas. Once the pathogen arrives, the right weather conditions (cool and wet) must be present for the disease to become established and spread.


There are a few tomato and potato varieties with resistance to late blight. Look for resistant varieties in your seed catalog for next year. 

Thursday, August 24, 2017

EAB found in Martin County

Jeffrey Hahn, Extension Entomologist

The Minnesota Department of Agriculture (MDA) reported earlier this week that emerald ash borer (EAB) was confirmed in Martin County in the south central area of the state on the Iowa border. Because the nearest infested areas in either Minnesota or Iowa are several counties away, the infestation is the result of someone moving infested ash into the county.
Watch for EAB galleries and other
symptoms of their presence.  Photo: Jeff
Hahn, University of MN Extension

EAB was first found in Minnesota in 2009. Since then, it has spread and is now found in 16 counties.  EAB is a very destructive invasive insect that threatens all native ash in the U.S. Ash is a very important resource in Minnesota where about 1 billion ash trees occur, one of the highest numbers of ash trees in the country.

People can greatly reduce the chance for EAB to spread by buying their firewood locally and avoid transporting it. Burn it where you buy it. It is equally important to observe any quarantine restrictions for the movement of any ash products that may occur in your county. Be aware of the symptoms of EAB and report any suspicious infestations to the MDA’s Arrest the Pest line at 1-888-545-6684 or arrest.the.pest@state.mn.us.

For more information about EAB, including symptoms of infestations, see Emerald ash borer in Minnesota.

For the original MDA news release, go here.

Wednesday, August 23, 2017

Add fall color and benefit butterflies by planting native grasses

Contact: Diane Narem, Horticulture Researcher, dmnarem@umn.edu

Although summer may be coming to a close, it’s not too late to add some charm and color to your
Little bluestem Blue Heaven™
garden this fall with some perennial native grasses. Native grasses can liven up a planting with their interesting shapes and seasonal color changes and benefit multiple types of wildlife, including butterfly and moth species.

According to U of M Extension Horticulturalist Mary Meyer, native grasses require one month of good growing conditions to establish in the fall. This means you can safely plant grasses until mid-September. Extra watering may be necessary during hot or dry spells in the fall. Container plants with well-established root systems are the best choices for fall plantings.

“Many grasses are just beginning to flower in August," Meyer said. "They will soon start their fall color change, so August and early September can be peak season for native grasses".

Not only do they add beauty to your landscape, but grasses are also low maintenance and provide benefits to the environment. Once established, native grasses need little additional water because they are naturally drought tolerant. They also do not require fertilizer or added nutrients. They minimize soil erosion and increase organic matter, creating better soil conditions.

Native grasses provide habitat for wildlife, such as birds, native bees, and butterfly and moth larvae. Many species of butterflies and moths use native grasses as host plants during their caterpillar stage. The larva feed on native grasses, and some build shelters in the leaves and stems, while others hide at the base of the plant. Many of these species survive winter as larva and take shelter within grass plants or burrow just below the soil surface.

Native grasses that provide fall color and food for butterfly and moth larva include little bluestem, big bluestem, switchgrass, and Indiangrass. You can find these plants and others at garden centers throughout Minnesota. For more information on native grasses from the University of Minnesota Extension: Ornamental Grasses for Cold Climates

Friday, August 4, 2017

Cicada killers common now

Jeffrey Hahn, University of Minnesota Extension

A large solitary wasp called a cicada killer, Sphecius speciosus, is common in many areas of Minnesota now. It ranges in size from 1 – 1 ½ inches long. It has a black abdomen with yellow bands, a reddish brown thorax with reddish brown legs and amber colored wings.
Cicada killer with a captured cicada.  Jeff Hahn, U of M Ext.

Some people mistakenly believe they have found a European hornet which is also a large wasp. However, European hornets are social insects living in nests they usually build in tree cavities; they can also be found within homes and other buildings. European hornets do not occur in Minnesota.

Cicada killers nest in the ground, typically in well-drained, light soil exposed to full sun. They are a solitary wasp, meaning that there is only one wasp per burrow. However, cicada killers are gregarious, so there are typically many of them in a small area.

These wasps prey on cicadas. Cicadas are stout, winged insects that are common during the summer. A cicada killer uses her stinger to paralyze a cicada she captures. She carries it back to her nest where it is food for her young. Once the larvae are full grown, they pupate and remain in their burrows until next year.                    

Despite their size, cicada killers are not dangerous to people. Females have stingers but they are not aggressive and ignore people. They do not have an instinct to protect their nests (like yellowjackets and honey bees) and you can walk among them with little worry. Of course, if you provoke a cicada killer or it feels threatened, it can sting to protect itself.
Cicada killer nests can become very abundant in a small area. 
Jeff Hahn, University of Minnesota Extension

Fortunately, cicada killers are just annoying. Their tunneling can be unsightly but does not kill lawns. It is not impossible for their burrowing activity to undermine patio bricks but that is not common.

If you have cicada killers nesting on your property, there are a couple of options to consider. The first is to ignore and tolerate them and let them run their course. Remember, there is very little risk of stings and they will go away on their by the end of the summer. The area can be roped off, in necessary, to keep people away from the nests.

Another option is to treat the nests. Treating the general area is not very effective. Instead, apply an insecticide into each individual nest entrance. Dusts are most effective, although sprays can help reduce numbers. Be sure the product you use is labeled for you use on turf. Effective active ingredients include permethrin and carbaryl. You can also hire a lawn care company to treat the cicada killers.

Wednesday, July 5, 2017

Dealing with Japanese beetles

Jeffrey Hahn, Extension Entomologist

If you had problems last summer with Japanese beetles on your property, the odds are very good they will be pests again this year. In fact some people are already seeing them in high numbers. So the question is what can a gardener do?

Killing individual Japanese beetles is actually easy but the problem is what to do when there are a lot of them. There is no one guaranteed method for treating Japanese beetles. It is best to use as many different management steps as possible to improve your chances of keeping Japanese beetle feeding to tolerable levels.

Have you checked your garden recently for Japanese beetles?
  Photo: Jeff Hahn, University of Minnesota Extension
If you have a small garden, physical removal can be a good option, especially when only small numbers are present. However when Japanese beetles are numerous, it becomes impractical to handpick them every day. Another non-chemical option is to place a cheese-cloth, or similar type of fabric, around valued plants to exclude the beetles.

There are a few low impact insecticides available. Pyola is effective but this product is short-lived and repeat applications are necessary. Neem oil is also an option. It helps deter Japanese beetles but is less effective when large numbers are present. Both of these products can be toxic to pollinators so be sure to apply them when bees are not active.

Thinking of using traps to control Japanese
beetles? Save your money, they are not
effective.  Photo: Jeff Hahn, U of M Ext.
There are a variety of residual insecticides that you can use, like permethrin or carbaryl (Sevin). To protect bees, apply insecticides during late evening after bees are no longer active. The products should be dry by morning when bees become active again. If you are trying to protect a large tree, you may need to have it treated by a landscape or tree care company.

Deciding whether to treat trees and other plants will depend on how many of the leaves are still intact. If nearly all of them are already chewed up, then spraying does not help protect the plants. If there are still a lot unaffected leaves, then it is worth your while to treat them.

Keep in mind that trees that are healthy and mature are not going to be killed from just one year of feeding. Trees are quite resilient and can tolerate a lot of defoliation. If trees has been recently transplanted or are already under stress, it is a good idea to protect them from any additional damage.

What you don’t do is just as important as what you do try. Some people like the idea of using Japanese beetle traps to protect their plants. While these traps can capture an impressive number of beetles, the traps are attracting more beetles than they catch. Research has shown that when these traps are used in home gardens, damage is not reduced but in fact is likely to increase. Likewise, companion planting has been demonstrated to be ineffective in protecting plants from Japanese beetle feeding.

 For more information, see Japanese beetle management in Minnesota.

Poison hemlock: Highly toxic - use caution


(From http://www.myminnesotawoods.umn.edu/poisonhemlock/)

Poison hemlock (Conium maculatum) is an invasive plant native to Europe and North Africa. It is highly toxic (i.e., fatal) to humans and animals. Poison hemlock requires considerable sunlight to flourish and is found often near railways, rivers, ditches, field edges, farms and bike paths. It is a biennial plant (having a two year life cycle), and is unlikely to grow in very shady areas or places that are frequently mowed. Read more...