CO-Horts Blog

Wednesday, June 29, 2022

Host an Aphid Watch Party This Summer and Look for Biodiversity

Posted by: Lisa Mason, Arapahoe County Extension

Yes, you read that right! Get excited about watching aphids on your plants this summer just as you get excited about your favorite TV show or a new moving coming out! You’re probably asking, “Why would I watch aphids on my plants? Aren’t they a nuisance pest?”

The definition of a nuisance pest depends on who is asking. For instance, if you are a hungry lady beetle, aphids are a feast waiting to be had!

Except for a few species, most aphids cause very little plant damage. Aphids are host-specific meaning that each of Colorado’s 350 aphid species will only feed on certain plants.

Aphids are also one of the insects that excrete honeydew, which is a sweet, sticky substance that coats the plants and anything underneath the plant. 

So, why would you watch aphids on your plants? Aphids attract a wide variety of beneficial insects to our gardens. An aphid infestation can be a hotspot to observe biodiversity in your garden or landscape. For instance, while I was writing this article, I found aphids in my backyard on a sand cherry! So far, I’ve seen lacewing eggs, lady beetle pupa, a katydid nymph, syrphid fly smears, and other insects feeding on the honeydew.

Aphids (Aphis nerii) on a milkweed plant. Photo: Lisa Mason

Here are some fun observations you may witness while you are watching aphids:

Predators Hunting Aphids

Lady beetles (Family: Coccinellidae), also known as lady bugs, are a common insect you’ll find preying on aphids and other soft-bodied arthropods. We have approximately 80 different lady beetle species in Colorado. Lady beetle larvae have a completely different appearance than the adult beetles because they complete a full metamorphosis (egg, larva, pupa, and adult). The larvae look similar to little dragons or alligators, and they are ferocious predators! Their goal is to eat as much as possible! Convergent lady beetle larvae can devour up to 50 aphids a day, often consuming their weight in aphids (Hoffman and Frodsham, 1993). Other species such as the seven-spotted lady beetle may feed on higher numbers of aphids.

Lady beetle larvae. Photo: Melissa Schreiner

Lady beetles are a natural control option for aphids found in their environment. They are available for purchase at garden centers, but keep in mind that lady beetles can fly away. Since they are so mobile, lady beetles for purchase may not be too effective. However, purchasing and releasing lady beetles can be a great activity for children to help inspire an appreciation for insects and their role in our environment. The lady beetles for purchase are the convergent lady beetle, a native species.

Female lady beetles often lay eggs near an aphid infestation, so look for groups of dark yellow or orange-colored eggs that are oval-shaped and approximately 1 mm long. 

A lady beetle larva preying on an aphid. Photo: Melissa Schreiner

Lacewings (Family: Chrysopidae) are another common predator seen feeding on aphids. Just like lady beetles, the larvae of lacewings are ferocious predators! They earn the nickname “aphid lion” for a reason. In addition to eating up to 200 aphids per week, they can also feed on caterpillars by capturing them with their pair of hooked jaws.

Both green and brown lacewings can be found in Colorado. The adults have long, skinny bodies with membranous wings that that extend over the body forming a triangular or tent-shape.

Lacewings are also available for purchase as a biocontrol for the home garden. They can be more a more effective biocontrol option because they are available as eggs. When they hatch, the larvae will stay in the same place to feed until they reach adulthood.

Lacewing eggs. Photo: Lisa Mason

 Lacewing larva. Photo: Lisa Mason

Syrphid flies are another insect that feed on aphids as larvae, but they are quite elusive. Larvae can feed on 100-400 aphids. They are nondescript, grub-like larvae that vary in color. They leave behind excrement in their path that looks like a black, shiny streak known as a “syrphid smear.”

The adult form of syrphid flies is commonly seen visiting flowers with nectar. They often look like wasps and bees because they exhibit Bastian mimicry i.e., predators may avoid these syrphid flies because they look like stinging insects, though the syrphid flies are harmless. You can differentiate them from wasps and bees by looking for their giant eyes that extend almost to the top of their heads, only one pair of wings, and short antennae.

Syrphid fly. Photo: Lisa Mason

Tiny, parasitoid wasps will prey on aphids by laying eggs inside the aphid. The wasp larvae feed on the aphid. Parasitoid wasps cannot sting people, but they are deadly to aphids! The wasps are so small that they may be hard to observe, but you might see the remnants of them when you see dead aphids on the plant. 

Insects Feeding on Honeydew

Aphid infestations also attract a wide diversity of beneficial insects that feed on the sweet honeydew. You might observe a variety of wasps, ants, flies, and beetles all feeding on honeydew.

Ants and aphids often have a mutually beneficial relationship. Honeydew can be a major food source for ants, and the ants want to protect that food source. Since aphids are easy prey, ants will protect aphids from prey, and in some cases, protect them from fungal pathogens (Nielsen et al., 2009; Rathcke et al., 1967).

Aphid Reproduction and Life Cycle

Most aphids are wingless in a colony. You may observe winged aphids when they need to seek out new plants. Aphids reproduce at an astounding rate because reproduce both sexually and asexually. During the summer, you are likely to see aphids produced by females in asexual process called parthenogenesis. The female aphids give birth to aphids without fertilization. These aphids share the exact same genetics. Later in the season, the colony will produce male aphids to mate with female aphids that are able to reproduce sexually. The female will lay fertilized eggs that overwinter. Many aphid species will complete their life cycle on one plant host. Other species will overwinter on one species of host plant, and after hatching the spring, they will fly to another species of host plant. See Table 2 of the Aphids on Shade Trees and Ornamentals fact sheet for a list of aphids that have two host plants.

Rose aphids (Macrosiphum rosae) on a rose bush. Photo: Melissa Schreiner

Benefits of Attracting Insects in Your Landscape

Aphids and other pest insects serve an important role in the food web in our garden ecosystems. Just like predatory insects, birds can help keep the pest populations down. Most terrestrial birds rely on insects for a major component of their diet. Hummingbirds will catch up to 2,000 insects per day! They feed on aphids, mosquitos, and a variety of other insects. Consider supporting insects and birds in your landscape by planting a diversity of flowers with nectar and native plants, providing habitat spaces and water sources, and minimizing or eliminating the use of pesticides in the landscape.

Aphid Control Options

Beneficial insects are a great control option for aphids! A few other options are available if additional control is desired. Using a hose with a strong jet of water on the plant will knock aphids down. Since they are a soft-bodied insect, the impact from the water will kill many of them. Horticultural oils are effective at killing overwintering eggs. A variety of insecticide products are available, but use caution because many will kill the beneficial insect predators in your garden. Look for non-persistent contact products like insecticidal soaps that are safer for beneficial insects. As always, follow the label explicitly so that the product is applied effectively and safely. For more information, check out the CSU Extension fact sheet, Aphids on Shade Trees and Ornamentals.

Enjoy Your Backyard Biodiversity!

Have fun making observations this summer. Share photos on social media! Use the hashtag #AphidWatchParty


Hoffmann, M.P. and Frodsham, A.C. (1993) Natural Enemies of Vegetable Insect Pests. Cooperative Extension, Cornell University, Ithaca, NY. 63 pp.

Marvin, D. E. (2018) Hummingbirds as Pest Management Partners? New York State Integrated Pest Management, Cornell University.

Nielsen, C., Agrawal, A. A., and Hajek, A. E. (2009) Ants defend aphids against lethal defense. Biology Letters 6: 205-208.

Rathcke, B., Hamrum, C., and Glass, A. W. (1967) Observations on the interrelationships among ants, aphids, and aphid predators. The Michigan Entomologist, 1(5), 169-173.

Schuh, M. 2022. Lacewing. University of Minnesota Extension.

Statewide Integrated Pest Management Program. (2002) Syrphids (Flower Flies, or Hover Flies). University of California Agriculture and Natural Sciences.

Warner, G. (1993) Syrphid Flies (hover flies, flower flies). Washington State University.

Thursday, June 23, 2022

Keeping Cats Out of Your Garden

Keeping cats out of your garden

By Rhiannon Rowe, Eagle County CMG 


As a lifelong cat lover, I hate hearing about how much of a nuisance they can be to gardens and yards. Not to mention the stress they can put on the local bird population! Before I jump on my soapbox about keeping your cats indoors, I know that many cats prefer to be outdoors and are not suited for an indoor lifestyle. With that being said, the best we can do is find ways to deter our feline friends from wreaking havoc on our plants. Cats can smell 14 times better than humans so the best place to start would be planting or placing scents around the yard that cats do not prefer. Citronella, lavender, peppermint, rosemary and chives are all common plants that cats are not fond of. Added bonus is that many of them attract bees and smell great to us! Coffee grounds and citrus peels are also a good idea, plan to replace them often to keep the effect going.

There are a few commercial deterrent sprays you can find in pet stores or online. Just make sure they are safe to use around plants before you start spraying. Barriers can also be effective by physically keeping the cat away from your garden although they can make it tough to reach your plants. Netting can help protect your younger plants as well as putting a ring of pine cones or anything prickly around the plant as cats don’t like to walk on surfaces that aren’t soft. A friend of mine likes to put plastic cutlery around her garden and swears it helps!

Water can be used in a few different ways. Motion activated sprinkler systems can work as well as posting up with a SuperSoaker to catch the cat in the act. Cats aren’t fans of water and it shouldn’t take more than a few times for them to realize that they aren’t welcome! Using water to wash away an intact male cat’s urine scent can also help as well as removing anything that a cat is using to mark his territory.

There are several other ways to deter cats from a garden but these are my favorites! If these ideas aren’t helping, it may be time to speak to your neighbors about their cat’s behavior and try to come to an understanding. If you aren’t sure who the cat belongs to or if it is a feral cat, contact your local shelter. They can pick up the cat and check for a microchip. If the cat is feral, they can help you set a humane trap to try and remove the cat from your premises. 

Finally, cats are conditioned to stay in an area that is comfortable and welcoming to them. If there is food present, their hunger is taken care of. If there is loose dirt, they have found a litter box! If there are fun things to chase such as mice and birds, they have plenty of entertainment! Finding ways to take these luxuries away will help the cat realize that they need to move on and find a new place to enjoy.

Thursday, June 16, 2022

Hoppin' to it with grasshopper control


Posted by Todd Hagenbuch, Routt County CSU Extension

You’re wondering why an Extension blogger from Routt County, of all places, is submitting a piece on grasshoppers, right? Surely our area, home to amazing snows, Ski Town USA, and pristine, green hay meadows doesn’t worry about hoppers, right? Wrong. Look at this map of the state and you’ll see that our gardeners, ranchers, and wildlife managers all have to deal with the impacts of grasshoppers and the damage they cause more than most of the state.

2021 USDA Colorado Grasshopper Count
You might also be wondering where the data on the map came from. Did you know that the USDA counts grasshoppers on range and cropland to figure out how many there are in areas of the state? In NW Colorado, that job has been done for years by two people who are also Colorado Master Gardeners. As people who understand plants and insects, the two different CMGs who have done this job have been key to the Routt County Extension Office helping local landowners decide if and when they should apply control measures.

Control measures are generally recommended in crops and in range if numbers exceed 15 grasshoppers per square yard. Today my CMG friend and USDA grasshopper counted 43 hopper nymphs per square yard (!) at one site, and another intrepid CMG shared the photo below of hoppers in a dog park in Steamboat Springs. How many nymphs can you count in this area, which is just over a square yard?!?

How many nymphs can you count in this square yard?
Photo Courtesy CMG Donna Segale
As a gardener, you know that just a few hoppers can cause a lot of damage, especially after they’ve molted several times and have become ravenous adults. Large-scale spraying efforts, like I’m recommending for rural landowners and ag producers in Routt County, isn’t as desirable for garden situations, especially if you’re growing veggies. That begs the question: what can I do as a gardener when the swarm is heading my way?

Granular baits laced with insecticides are one way to help control grasshoppers. When the insect eats the bait, they die and become part of the organic matter of your garden. As there is still insecticide involved, however, some folks would like another option. Covering your garden, or at least the rows in it with a lightweight, floating row cover is an excellent measure, making sure hoppers can’t get in but light and air can.

One of the most unusual but coolest control measures I’ve seen involved a two-fence approach, where the garden was located inside a fenced area with another fence located about 15’ outside the inner fence. Each fence was about 6’ tall and not only kept elk and deer out of the garden, but the area between the fences housed about 50 hens who patrolled the area. As hoppers flew in, they were immediately gobbled up by the chickens and rarely got as far as the garden. The ‘chicken moat,’ as the owner called it, was a creative, useful idea that brings me a smile every time I think about it.

If you have grasshoppers, think about creative ways you can limit the damage they do to your yard, garden, or property because they can be a formidable enemy. Also, for more information on grasshopper control, hop on over to CSU Fact Sheets 5.536 and 5.535 to learn more ways to keep this insect at bay.

Tuesday, June 7, 2022

My Lawn Has Never Looked This Bad!
Tony Koski, Extension Turf Specialist

Winter desiccation (aka "freeze-drying); made worse because the thatch layer was a little
thick? Probably some rabbit activity, and maybe some cranberry girdler as well? That 
combination will kill grass in the best of lawns during a severe winter

It seems like nearly every lawn up and down the Front Range has experienced some level of turf injury this spring – more than I can remember in my 30+ years at CSU. Many have been cared for by avowed lawn geeks (like Alison’s lawn, pictured here!). These folks are used to turf perfection, so are especially shocked, dismayed and embarrassed by the spots and patches that have appeared in their normally picture-perfect lawn. What has caused so many beautiful (in 2021, anyway) lawns to become so bad this spring that owners are reluctant to send me pictures of them? Pinning down the exact cause of the turf damage without visiting the lawn can be difficult, but if you are seeing dead patches in your lawn this spring it’s almost certainly one of the following problems. Lawns that were seeded or sodded in 2021 (especially later in the year) were more likely to be injured. If the lawn hasn’t greened up by this point in time – especially after the recent rain – then it’s almost certainly dead, with the solution being new sod or seeding (go here
for some videos on seeding and sodding lawns

Winter Desiccation (freeze-drying)
This is probably the most common cause of lawn damage this spring, most likely to occur on areas of the lawn that were drought-stressed going into winter last fall.  Turf stressed by poor irrigation coverage in 2021 (broken/plugged/low/crooked heads, low pressure, bad spacing) was more susceptible to being damaged by the dry, cold, sunny, windy winter conditions we experienced this year. Lawns with thick layers of thatch also appear to be more likely to have been injured. Check spots that are dead now for irrigation coverage deficiencies – before re-seeding or sodding. You rarely can detect non-uniform water application by simply watching your sprinkler system (“It looks like water is going everywhere” you say…but it’s not going everywhere uniformly). Don’t blindly trust your “irrigation guy”/sprinkler company when they tell you that everything “looks fine”. To be certain about uniformity of water application, it has to be measured by a formal or informal irrigation audit (here’s a DIY method to help you identify dry spots in your lawn).
This turf died from winter desiccation. When you can see where the
irrigation heads are, you know there are irrigation coverage problems. The
dead areas in this lawn were drought-stressed LAST FALL - which resulted
in the turf succumbing to the severely dry and cold winter. The turf also 
survived around the young tree - because of winter watering of the tree.

Insect Feeding Damage

Feeding by cranberry girdler (

This lawn was weakened by cranberry girdler feeding
last fall (2021); the cold, dry, windy winter resulted in
the death of the stressed turf

) or white grubs ( last fall could have gone undetected and so weakened turf root systems that the turf more easily succumbed to winter desiccation. Dead turf that peels up easily from the soil surface was likely fed upon by these insects. If the lawn hasn’t greened up by now, it’s dead and the only alternatives are to seed or sod the affected areas.

Turfgrass mites damaged this lawn. Notice the
lack of mite injury in the neighboring lawn (top
of photo) which received winter watering.
Mite Feeding

Winter mite activity can kill large areas of turf, usually on lawns facing south or west. The damage caused by winter mites can look identical to winter desiccation injury: orange or brown grass (early death), changing to grey/silvery grass (dead for awhile). Mite-damaged turf will still be strongly rooted, distinguishing it from damage caused by root-feeding insects. Even when mites are actively feeding in lawns, they can be difficult to detect – so mite injury is often confused with other types of winter damage. The best control for mites is late winter/early spring irrigation, or a few good snowfalls or rainy spring weather. Since they aren’t insects, insecticides don’t provide great control of turfgrass mites.

Rabbit Injury

Look for rabbit pellets (aka "poop") in the brown spots
in your lawn as a sign of rabbit activity.

Rabbits feeding is often concentrated in small areas of the lawn. The persistent feeding and deposition of urine can kill small to large areas (depends on how many rabbits are in the yard) over the winter. Rabbits can be trapped and relocated (where legal; check with local animal control for the laws that apply where you live); applying the fertilizer Milorganite to your landscape (lawn and garden beds) can repel rabbits - if they have somewhere else to feed and live.

Rabbit activity can result in the death of large areas in the home lawn.

While it’s good to know what may have killed parts of your lawn – so that you can take measures to prevent the same thing from happening in the future – the “fix” is generally the same: repairing the dead areas by seeding or sodding (here and here, for how to do this).

Monday, June 6, 2022

Is It Too Late to Plant A Veggie Garden?


By Yvette Henson, San Miguel Basin Extension

Timing is critical when planting a vegetable garden, especially in the short-season areas of our state where every day counts to get a harvest.  But what if you missed the recommended planting dates for your area?  Is all hope lost for you to have a garden this year?  The answer is: “It depends”.  It depends on how short your season is, your average summer temperature range and what types of crops you plant.

Correct timing for planting a veggie garden matters- the late planted newly sprouted peas in the background didn't produce by the time hard frost arrived.
 (photo by Yvette Henson)

To make this article easier to understand I want to first define some terms: 

  • “warm-season crops” are crops that need warmer temperatures for seeds to germinate (50-90 degrees F) and for the plants to grow to maturity (around 90 degree days and at least 50 degree nights).  Warm-season crops will not tolerate frost.  
  • “Cool- season crops” need a cooler temperature range for seeds to germinate (40 - 80 degrees F) and will not grow well with extended temperatures above 80 degrees during the day (60-65 degrees F is best).  Temperatures above this may result in the plants bolting (forming a flower stalk and eventually seeds) or in the plants having a bitter taste. They will tolerate frost and in fact, develop better flavor with cold night temperatures.  
  • In general, “short-season varieties” will reach maturity in 80 days or less. 
  • Choose varieties based on the average frost-free growing period for your area as well as your average day time and night time temperatures of your location.  You can find this information at

Now, back to the question at hand “Is it too late to plant a garden and get a harvest this year?”

It is likely too late to plant and get a harvest of warm-season crops like corn, peppers, eggplants, melons (particularly watermelons).  These also require a long season to mature. Let’s use winter squash as an example.  Winter squash require warm temperatures around 90 degrees during the day and at minimum 50 degrees at night.  They also require around 90-120 days to mature.  Although there are short-season, somewhat cold-tolerant varieties of most warm-season crops that will improve the odds to get a harvest in short-season areas with cool night temperatures, these varieties still need the basic conditions for good growth of warm-season crops.  

A selection of winter squash, both a warm-season and a long-season crop         
(photo by Yvette Henson)

If you have a longish, frost-free growing season with warm summer temperatures, you could still plant and get a harvest of warm-season crops like bush green beans or summer squash.  Most varieties mature anywhere from 45- 65 days. 

These warm-season bush beans mature in about 50-55 days
(photo by Yvette Henson)

If you live in a location with summer day-time temperatures that reach or exceed 90 degrees then is too late to plant and get a good harvest of cool-season crops like lettuce, arugula, spinach, mustard greens, summer radishes, etc.  These are all cool-season crops that may bolt and/or develop a bitter taste in the heat of summer.  You could wait until July or early August to plant quick- maturing, cool-season crops like peas, lettuce, fall radishes, etc.  These will be ready once the cooler temperatures of fall arrive.  

Beaujolais spinach does well planted late to mature in cool fall weather
(photo from Fedco Seeds)

If you live in an area of the state with a short frost-free growing season and cool nights, you may still be able to plant and harvest crops like cabbage, broccoli, turnips, rutabagas, beets, carrots.  Just be sure to check the days to maturity on the packet of seeds, keeping in mind that cool temperatures increase the actual days to maturity.  I have a 100 day growing season and cool night temperatures, so I prefer to plant peas the first of July.  They will be ready to harvest in the cool of fall and will be sweeter.

This 'Early Jersey Wakefield' cabbage is easy to grow and is ready to harvest in 70+ days
(photo by Yvette Henson)

Also, keep in mind that some crops grow best with certain day lengths.  See my previous article titled: "Day Length and Plants". 

This isn’t an exhaustive list for sure and I would love to get the input of experienced gardeners.  In the comments give your growing conditions and crops that you can plant later than the recommended planting times for that crop.