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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...