Tag Archives: Phenology

Ornamental Pest, Sawflies, Shrubs

What’s Eating My Roses in Spring? — Sawflies

If you’re seeing insect damage on your roses this spring, you aren’t alone and there are a number of early-season insect that can catch our attention.  For example, a number of caterpillars can occasionally be spotted on roses in spring, such as the rose plume moth (Cnaemidophorus rhododactyla).  There’s also the non-native rose leafhopper (Edwardsiana rosae) which can cause faint speckling on leaves. Later in the growing season, rose chafers (Macrodactylus subspinosus) and the notorious Japanese beetle (Popillia japonica) can be a concern.

Perhaps the most noticeable damage to roses in spring is caused by the larvae of sawflies.  These insects cause two types of damage: “windowpane” damage when they only feed partway through foliage and leave the upper leaf surface intact or small holes or notches when larger larvae chew entirely through the leaves.  In the Midwest, there are three different species of sawflies that can commonly be encountered on roses in spring: the roseslug sawfly (Endelomyia aethiops), the curled rose sawfly (Allantus cinctus), and the bristly roseslug sawfly (Claudius diffiformis).  To the naked eye, the larvae (up to ~ ½ inch long, pale greenish, and caterpillar-like) and the adults (~ ⅓ inch long, dark-colored, and wasp-like) all look similar.  However, determining the exact species under magnification can be helpful to understand the potential impacts on your roses.

Classic “windowpane” damage caused by sawfly larvae on roses. This damage occurs when small sawfly larva only feed partway through the leaves. Photo credit: PJ Liesch, UW Insect Diagnostic Lab.

The roseslug sawfly (Endelomyia aethiops) is the commonest of the three sawflies that I see samples of at the UW Insect Diagnostic Lab.  The larvae of this species have a smooth texture and brownish head capsule; their bodies are translucent and they usually have a pale greenish color due to ingested green leaf material.  Some good news about the roseslug sawfly is that this species only has a single generation in spring.  Their damage tends to be mostly just a minor cosmetic issue.  As the plants really take off in late spring, they tend to “shrug off” this damage and it’s quickly covered up by new growth.

Larva of the roseslug sawfly (Endelomyia aethiops) feeding on the underside of a rose leaf. Photo credit: PJ Liesch, UW Insect Diagnostic Lab.

The curled rose sawfly (Allantus cinctus) goes through two generations early in the growing season.  Similar to the roseslug sawfly, their feeding damage tends to be minor and plants are usually able to chug along just fine.  The larvae of the curled rose sawfly also are pale green with a brownish-orange head capsule.  They do have tiny spots on their bodies, but these are only visible under high magnification.  This species tends to feed while curled up and they also chew notches on the edges of leaves which can help distinguish this species from the other two sawflies.

Larva of a curled rose sawfly (Allantus cinctus) on the underside of a rose leaf. Note the notches on the edges of leaves which can serve as a clue to help identify this species. A rose leafhopper nymph is also present to the left of the larva. Photo credit: PJ Liesch, UW Insect Diagnostic Lab

The third sawfly commonly seen on roses also tends to be the most problematic—the bristly roseslug sawfly (Claudius diffiformis).  Unlike the first two sawflies, this one can continue to reproduce throughout the growing season.  Because they go through many generations per year, their damage can accumulate over time and tends to be more notable.  Like the other two sawflies, the larvae of this species are also pale green with a brownish head capsule, but they are covered with fine, hair-like bristles when viewed under magnification.  Very few sawflies have a hairy or bristly appearance like this, which helps distinguish this species on roses.

Larva of the bristly roseslug sawfly (Claudius diffiformis). Note the fine hair-like bristles which help identify this species as seen in this magnified photo. Photo credit: PJ Liesch, UW Insect Diagnostic Lab.

If you do bump into these sawflies on your roses in spring, they’re pretty easy to deal with.  Options for managing them include:

  1. Do nothing. Since damage from the roseslug and curled rose sawflies tend to be minor, established plants often tolerate these insects with little/no intervention.
  2. Squishing, hand-picking or knocking them into a container of soapy water (be mindful of thorns…)
  3. Insecticidal soap or horticultural oils such as neem oil.  Make sure to achieve good spray coverage.
  4. Pyrethrins or spinosad—both are organic spray options. Note that Bacillus thuringiensis kurstaki (which works well against caterpillars) does not work against these sawflies.
  5. Conventional sprays from the hardware store/garden center labelled for use on ornamental shrubs and landscape plants.  Use caution since these products tend to have broader-spectrum of activity and can pose greater risks to bees and other pollinators such as butterflies, moths, beetles, and many flies.

  

Aquatic Insects, IDL Highlights, Odd Insects, Phenology, Uncommon Insects

Insects on the Snow

Despite the season, there’s a surprising number of insects and related arthropods that can be found on the snow during the winter months here in the Midwest.  Such creatures have fascinating life histories and special adaptations (such as natural “antifreeze”or cryoprotectants) that allow them to not only survive, but remain active at low temperatures.  Even these adaptations have limitations and winter insects generally aren’t active if temperatures are below ~20˚F (-7˚C).  Most activity occurs on mild winter days when temps close to or just above freezing.

If you’re curious to learn more about the stories behind these winter creatures and others, I’d encourage you to check out Bernd Heinrich’s Winter World: The Ingenuity of Animal Survival. Read on to learn about some of our commonest “winter” insects in Wisconsin and nearby states:

Snow Fleas: If you follow this blog, you might recall the example of snow fleas from two winters ago.  These dark-colored springtails (Collembola) can sometimes be abundant enough to give large swaths of snow a sooty appearance.  Snow fleas can be common on mild winter days and if I’m out cross-country skiing in the Northwoods, I’m often more surprised if I don’t spot any.

Up-Close View of a Snow Flea. Photo Credit: Daniel Tompkins via Wikipedia

Snow Flies: One of the weirdest examples of a “winter” insect would be “snow flies” from the genus Chionea.  Despite their spider-like appearance, snow flies are actually a type of wingless Limoniid crane fly.  Being wingless and generally slow moving might sound like an easy target for predators, but by being active at cold temperatures these insects can actually avoid the many predators that feed upon related flies during the warmer months.  Interestingly, their physiology is so specialized, that these unusual insects can be active between about 20˚F (-7˚C) and 32˚F (0˚C), but if it’s a warm winter day with melting snow it can actually be too hot for them!  If you’d like a more detailed look at these insects, check out J.R. Schock’s article in The Kansas School Naturalist.

Snow fly (Chionea sp.) on the snow in northern Wisconsin. Photo credit: PJ Liesch, UW Insect Diagnostic Lab

Winter Crane Flies: I occasionally get reports of “swarming mosquitoes” on winter days, and perhaps you’ve bumped into a cloud of tiny delicate flies out in the snowy woods or on a mild fall or spring day.  What you’ve likely encountered are winter crane flies (Family Trichoceridae).  These delicate flies are related to mosquitoes but have no interest in blood.  The adults are simply trying to mate and the larvae are scavengers.  

A winter crane fly (Family trichoceridae) that landed on the snow. These can be spotted flying on mild fall, winter, and early spring days. Photo credit: PJ Liesch, UW Insect Diagnostic Lab

Snow Scorpionflies: In my mind, one of the more elusive winter insects is the snow scorpionfly.  Despite having “scorpion” in the name, these aren’t scorpions (or true flies for that matter).  Rather, they belong to a small order of insects (Mecoptera), which includes some bizarre examples, such as the common scorpionflies, hangingflies, and earwigflies.  Like the snow flies, the snow scorpionflies are also flightless and simply wander about on the snow when conditions are right.  In the Midwest, we only have two species from this group Boreus brumalis and Boreus nivoriundus, and both species are associated with mosses.

A snow scorpionfly. Elusive, but fascinating creatures. Photo credit: PJ Liesch, UW Insect Diagnostic Lab.

Aquatic insects: If you’re near open streams or rivers during the winter months, certain aquatic insects can sometimes emerge and be found on the snow.  Caddisflies and stoneflies are two of the commonest examples.  I recall ice climbing one winter’s night at Governor Dodge State Park west of Madison and reaching the top of a frozen waterfall only to spot dozens of adult “aquatic” insects active on the snow.  The conditions must have been just right that evening, as I also saw hundreds of tiny Cynipid wasps (from oak galls) on the snow as I descended the access trail from the climb.

Caddisfly on the snow near a Northwoods stream. Photo credit: PJ Liesch, UW Insect Diagnostic Lab

Spiders: Hexapods aren’t the only arthropods getting in on the winter fun.  Species from at least a half-dozen families of spiders can occasionally be spotted on the snow on mild winter days.  They might be pretty lethargic, but it’s still interesting to see creatures like that out-and-about on the snow.  The video clip below shows a spider I spotted on the snow in Northern Wisconsin on New Year’s Eve a few years ago when the air temperature was right around 30˚F (-1˚C).

 

  

Bees, Pollinators, Wasps and Bees

In Defense of Ground Bees

“Ground bee” season is officially here, but before we get any further, let’s clear up a few things about these insects.  Ground-nesting bees get a lot of undeserved blame for stings that they simply aren’t responsible for.  Despite their claims, many folks have probably never been stung by an actual “ground bee”.  Every year I get plenty of calls about “angry stinging ground bees” in late summer, but these are almost always ground-nesting yellowjackets (Vespula spp.).  Undoubtedly, if you stumble into an in-ground yellowjacket nest, you’ll be forced to make a hasty retreat from the area as the colony defends itself.  But those aren’t bees…

Entrance of a ground-nesting yellowjacket nest in late summer. These might be black and yellow, but they aren’t bees… Photo credit: Jeff Hahn, U. Minnesota.

While yellowjackets and bees are related (both belong to the insect order Hymenoptera along with the ants and sawflies), they belong to completely different families.  From a standpoint of taxonomic classification,  mixing up yellowjackets and bees would be like confusing dogs for cats, raccoons, or walruses (all belong to separate families within the mammalian order Carnivora).  We do technically have social, ground-nesting bees that can be ornery if disturbed (i.e., bumble bees), but folks generally recognize bumble bees by their large size and robust appearance.  

A solitary ground nesting bee guarding the entrance to its nest in a city park in Middleton, WI. Photo credit: PJ Liesch, UW Entomology.

So what about these other “ground bees”?  Most bees (about 2/3 of all bees) are actually ground-nesting species.  In the Midwest, we’ve got around 500 different bee species, meaning there are hundreds of ground-nesting species around us.  Our common ground-nesting bees include species of: cellophane bees, mining bees, squash bees, longhorned bees, sweat bees, and others. For the most part, these ground-nesting bees are solitary creatures that live alone, although many nests can occur in the same general area as shown in the video clip below.  They often prefer sunny, open areas with thin ground cover or bare, sandy soil and can be common in parks and home lawns.  

To a certain extent, solitary bees can be thought of as the insect equivalent of “preppers”.  Each bee digs her own nest—a small, bunker-like tunnel in the ground, which looks like an ant hill.  Not only do the females have to construct these shelters, but she has to gather all of the provisions needed for her young to survive inside—often in the matter of just a few weeks.  The female bees collect pollen and nectar from flowers to create a nutritious substance called bee bread, which they place into small chambers (cells) and lay an egg.  Once the eggs hatch, the young bees (larvae) have all the supplies they’ll need to grow and develop in their survival bunkers.  

Most of these ground bees have a single generation per year.  The adult bees are out and active for a short period of time (often a few weeks), before they’re done and gone for the year.  When they are active, our solitary bees can be excellent pollinators and can be more efficient than honey bees in some regards.  However, their pollination services often go unrecognized and unappreciated by the general public.  While news articles regularly sound the alarm about honey bee declines, we should really be much more concerned about the potential loss of our solitary bee species, as they’re more sensitive to disturbances, pesticides, and other stressors.

Post-jog entomologist next to five solitary bee nests. These bees are extremely gentle and unlikely to sting. This portion of a local park had thousands of solitary bees flying around. Photo credit: PJ Liesch, UW Entomology.

If you spot ground bees this time of the year, is there any reason for concern? No. Solitary ground-nesting bees are great to have around.  Being solitary nesters, these ground bees don’t have a large colony of  adult relatives to defend and they end up being surprisingly gentle and unlikely to sting.  Overall, they pose little risk to people or pets.  The best thing to do is to simply let them be and appreciate the pollination services they provide. 

If you’d like to learn more about Wisconsin’s bees, check on the Wisconsin Bee Identification Guide or the US Forest Service’s Bee Basics: An Introduction to Our Native Bees. If you have solitary ground-nesting bees in your yard and would like to teach others about these amazing pollinators,  click the image below to get a  sign to laminate and post:

A yard sign about wild bees

IDL Highlights, Odd Insects, Phenology

Snow Fleas: When a “Flea” isn’t a Flea

Fleas (Order Siphonaptera) can be an unwanted surprise—no one wants fleas on their pets or in their house.  Our commonest flea on both cats and dogs in the Midwest is the “cat flea” (Ctenocephalides felis), and this same species can also live on a wide range of wild animals.  Cat fleas may be annoying but can be controlled with a diligent multi-pronged approach: chatting with your veterinarian to pick a proper treatment for your pet and regular and thorough vacuuming. In heavy infestations, carpets and furniture may also need to be treated.  While fleas could be encountered anytime of the year, I see the vast majority of flea cases at the UW Insect Diagnostic Lab in late spring and summer.  In contrast, cases of fleas are few and far between during the winter months due to the dry conditions and lower temperatures which can be hard on these insects.

There is one type of “flea”, however, that I see regularly through the winter months—the “snow flea”.  Snow fleas (Hypogastrura nivicola   and close relatives) aren’t actual fleas and rather than a pest, these harmless creatures are a beneficial curiosity.  Their cold tolerance and ability to launch themselves into the air account for their nickname.

Up-Close View of a Snow Flea. Photo Credit: Daniel Tompkins via Wikipedia

The snow fleas we’re talking about technically aren’t even insects and belong to a closely related group of arthropods known as springtails (Collembola).  Springtails get their name from the furcula—an anatomical structure on the underside of their bodies, which springs downwards to catapult them up into the air.  Springtails can’t “jump” very far by human standards given their tiny size (less than a tenth of an inch long), yet they can easily launch themselves many times their own body length in a mere blink of an eye (video).

The snow flea is unusual for springtails (and most arthropods) in the fact that these creatures can remain quite active during the winter months.  As discussed in this post from last March, insects and other arthropods have a variety of strategies to make it through winter, ranging from migration to freezing solid in some cases.  The vast majority of arthropods are inactive during winter, but some, like the snow flea, seem perfectly content wandering out on the snow.  With their tiny size and dark grayish bodies, snow fleas can almost look as if someone had dumped out a pepper shaker on the snow.

Snow fleas in their element. Photo Credit: Christa R. via flickr.

Their ability to remain active at frigid temperatures is due to the concentration of specific proteins in their bodies, which serve as a cryoprotectant or natural “antifreeze”.  During the rest of the year, these creatures simply blend in amongst fallen leaves where they scavenge upon decaying materials and help with nutrient recycling.

These creatures are truly a winter curiosity if you haven’t encountered them before.  The next time you’re out snowshoeing or cross-country skiing, keep an eye out for these tiny acrobats on the snow.

Final Note: Overseas, our friends in the UK have different creatures they refer to as snowfleas—insects from the genus Boreus, which we’d call “snow scorpionflies” in our area.