Category Archives: Insect pests

Do Japanese Beetles Prefer Some Roses More than Others?

Colorado roses have been attacked by Japanese beetles for several years, leaving behind ravaged foliage and deformed flowers. Curiously though, some gardeners report that their roses suffer little to no damage from the insect. Are some rose cultivars less enticing to the Japanese beetle than others? This was the focus of Colorado State University’s 2016 observational study conducted at Littleton’s War Memorial Rose Garden. In the first year of this multi-year study, the following rose cultivars were not found to be damaged by Japanese Beetles: Angel Face, Debut, Hondo, Joseph’s Coat, Mardi Gras, Picotee, Popcorn, Prima Donna, Ralph Moore, Singin’ in the Rain and White Lightnin’.

Conversely, the following cultivars were observed to have the highest levels of Japanese beetle destruction: Pink Promise, Honey Perfume Whisper, Love and Peace, Day Breaker, Strike it Rich, Cherry Parfait, Eureka, Starry Night, Rainbow Knock Out, Lady Elsie May, Carefree Delight and June Lover.

Adult Japanese beetles destroy flowers at the same time bees are gathering pollen, making their impact even more significant. For this reason, CSU’s study identified roses with high Japanese beetle susceptibility and high visitation by bees. Topping this list were Rainbow Knock Out, Lady Elsie May and Strike it Rich. Also in this group were Prominent, Home Run, Easy Does It, Apricot Nectar, Gemini, Starry Night, Baby Boomer, Sweet Diana, Julia Child, Cathedral, Betty Boop, Mon Cherie and Cloud Dancer.

Early findings suggest that gardeners may be able to lessen damage to roses by planting cultivars that are less attractive to Japanese beetles. It also underscores the importance of close monitoring and care of plants to reduce the effects on pollination. In the future, additional information on why some cultivars are preferred over others is likely to emerge.

This CSU publication provides comprehensive information on caring for plants infested with Japanese beetles, the larvae stage effecting turf and more. An additional bit of advice – it has recently been found that crushing the Japanese beetle does not attract more beetles. So, while we’ve previously been advised to handpick and drown the insect in soapy water, feel free to stomp on them too. Since they are night feeders, they are easiest to find around dusk, when they are about to feast on your plants.

Written by Linda McDonnell, a Denver County Master Gardener

Note: The study cited in this post was presented to the Denver County Master Gardener Association by Dr. Whitney Cranshaw of Colorado State University in May 2017.

Photos courtesy of http://www.pixabay.com

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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New CSU Resource Targets Emerald Ash Borer

Colorado is preparing to battle a tiny insect that’s destined to change the way our urban forest looks. The Emerald Ash Borer (EAB) is already in Boulder County, and it’s only a matter of time before this destructive pest is found in nearby counties.

Every single ash tree that lines the streets of our neighborhoods is at risk. The EAB loves these trees that make up about 15 percent or more of all city trees.

The newest weapon in the fight is a mobile app. Colorado State University Extension and the Colorado Forest Service joined together to create a free app to help with early detection of the EAB menace.

The app is easy to download to Apple and Android-based mobile devices. Just search for “EAB/Ash Tree ID.”

The app walks users step-by-step through tree identification to determine if the tree is an ash and susceptible to the EAB. If it’s an ash, there are more resources for EAB symptoms, management and links to much more information.

It’s important for tree owners to be aware that ash trees are already at risk so they can be prepared. It’s better to consider management and treatment options sooner rather than later.

The EAB/Ash Tree ID app is the latest tool in the Colorado campaign to raise awareness about the insect pest that has already killed tens of millions of ash trees across the states.

The Be a Smart Ash program, sponsored by the City of Denver, started its communications campaign last year. The Colorado Department of Agriculture is also actively involved in fighting the EAB.

Laura Pottorff with the Colorado Department of Agriculture, leads an excellent one-hour webinar called “EAB: Myth or Monster” for Colorado Master Gardeners. The webinar (taped in May) is available through the CMG online continuing education program and will give master gardeners the information they need to provide research-based information to their communities.

All these resources will help tree lovers start thinking about their options for managing the ash trees in their landscapes. Approaches include replacing ash trees now, planting new trees to take the place of an ash tree in the future, and researching the insecticides to treat trees when the time comes.

By Jodi Torpey
A Colorado Master Gardener

Never Put a $10 Plant in a 10¢ Hole and Other Gardening Tips From Denver Master Gardeners

planting-1898946_1920Passionate gardeners love to talk about gardening, so with that in mind, we recently asked Denver Master Gardeners for their best gardening advice. Responses included tried-and-true practices, creative suggestions and good reminders for all of us as the gardening season kicks into full gear.

As the title of this post implies, we believe that great plants come from appropriate soil preparation. Amending with compost is often imperative as soil in our region tends to lack organic matter. But proceed with caution, as some plants, such as natives, prefer a leaner, less fertile soil. Too rich soil will cause these plants to underperform and often just flop over. It pays to do a little homework before planting, read seed package directions and have your soil tested.

One of our gardeners shared her recipe for amending soil: Add 1/2 a handful of both Alaskan fish pellets and triple super phosphate to half a bucket (such as a kitty litter pail) full of compost. Mix this into the planting hole for strong root development and beautiful blossoms.

A tip borrowed from the Rock Garden Society is to plant bare root. By gently shaking off most or all of the soil that the plant is purchased in, the plant will adjust to the garden soil without the soil interface (or boundary) that can occur between two soil types. Bare root planting promotes healthy root development.

mulch-1100555_1920Mulch, mulch, mulch is the mantra of many of our survey respondents as it keeps weeds out and moisture in. Add it like crazy each time you dig in the veggie, perennial and annual gardens and don’t forget container plants too. Small to medium-sized bark chips are popular, practical and pleasing to the eye. Natural mulch options are very effective, including not quite finished compost from the compost bin which will add carbon, feed living organisms, prevent water runoff and prevent compaction. Local arborists are often willing to drop off wood chips which would otherwise fill up the landfill. In the fall, mow over your leaves and spread them throughout the yard, they’ll breakdown by spring and add organic matter to your soil. Consider purchasing a chipper to grind up branches and other garden waste.

garden-hose-413684_1920Suggestions for responsible use of water include watering when the plant needs it instead of on a set schedule. Soaker hoses, often made from recycled material, are effective for watering plants at the soil line. Plants (even xeric ones)  need moisture to maintain healthy roots and overall strength, but often less than we think. For example, the Water Smart Garden at the Denver Botanic Gardens is watered about seven times during the season.

Weeding can feel like a no-win battle, but attacking weeds after a soaking rain makes the task easier. Pull weeds and unwanted volunteer shrub and tree seedlings when they are small, before they take hold in the ground or develop seed. Add stepping stones to the garden to avoid stomping on plants and compacting soil when working in the garden.

bindweed-1207738_1920A clever tip to eliminate stubborn weeds, such as the nasty bindweed shown here, is to take a large piece of heavy cardboard, make a cut from the edge to the center. Keep the cardboard as level as possible, slip the vine in the center and spray the vine with the herbicide of your choice or horticultural vinegar, which is sold in garden centers. The cardboard will protect surrounding plants from overspray. Aggressive weeds may require multiple treatments during the season.

One of our members recommends a tomato planting technique passed on through generations of farmers. She adds blackened banana peel to the soil and feeds them with skim milk upon planting and again one month after that. This less conventional practice yields her sweet, abundant fruit. While CSU can’t vouch for the scientific efficacy of this, the banana could be adding potassium and the addition of calcium may reduce the chances of blossom end rot.

plant-1585251_1920Growing tomatoes in containers is recommended for those with limited space. Select varieties which produce smaller fruit such as Patio, Cherry or Sungold. Use a large container (18+ inches in diameter), a sturdy support and a tray with casters. This allows plants to be moved from the path of hail or to optimal conditions. Container plants of all kinds benefit from weekly feeding of 1/2 strength fertilizer.

To keep pests at bay, try a thorough weekly spray of water during the growing season, including the walls of the house and fence. It’s a kinder way to shoo pests away.

If your vines need a sturdier trellis consider building one out of remesh, which can be found at hardware stores. It makes a durable, cost-effective support and can easily be cut with bolt cutters. It also can be attached to supports to create a dog run or create plant cages.

botanical-garden-413489_1920In the flower garden, invest in perennials for texture and dimension and add annuals for bold color. “Enjoy the randomness of some plants that choose their own spots to thrive” suggests one gardener. What a positive way to think of the seedlings that sprout up at this time of the year. Remember, too, that perennials may not come into their glory until the second growing season.

Gardening is a four season hobby. Winter watering of trees and shrubs will help keep them healthy and  veggie gardeners can get a jump on the season by using a cold frame or floating row cover to get an early start on lettuce, spinach and other cool season crops. Fall is a fantastic time to fertilize, aerate and over-seed the lawn. It is also an ideal season to divide perennials so that they settle in and are ready to take off in the spring.  Share your divisions with your neighbors, too, or trade for plants you’ve admired (envied?) in their yards. If you need more gardening space, solarizing or sheet composting is an excellent technique to ready a new garden bed and can be started throughout the year.

And lastly, a veteran gardener advises us to “Remember each little garden flower or planting arrangement is a moment in time. It will change. Don’t worry about it or take it too seriously.”

 

Written by Linda McDonnell with thanks to the many Denver Master Gardeners who shared their advice.

All photos courtesy of http://www.pixabay.com, a source of royalty free images.

Managing Aphids

June is a beautiful month in the landscape – welcoming peonies, iris, columbine, meadow sage and the inevitable explosion of aphids on perennials, shrubs and trees.

DSCN0534These soft-bodied insects resemble green, tan, red or black sesame seeds and can be found on stems, leaves (often underneath) or flowers. They feast on tender new growth, such as the fresh leaves of the bridal wreath spirea pictured here. Aphids suck sap from plants and in turn, leave behind a sticky, honeydew-like secretion on the foliage.

Depending on the plant, aphids can cause curled leaves, distorted flowers, reduced growth or little to no damage. A black mold may form on the sticky secretion. Ladybugs (or lady beetles) are natural aphid predators and can consume 50-150 aphids a day. The sticky secretion attracts ladybugs and other predators to the desired aphids.

What are options for controlling aphids?

  • Let nature take care of it. Ladybugs, green lacewings and other natural enemies can  eliminate modest sized aphid invasions.
  • Hose off the plant with a strong spray of water directed at the infested area. This is either lethal to the insects or if they survive, most won’t return. Given the size of the aphid population, it can take more than one forceful shower, a few days apart, to be completely effective.
  • Prune heavily infested limbs.
  • Control with nontoxic insecticidal soaps which are widely available in garden centers.
  • If possible, avoid insecticides which  also harm beneficial insects.

What about the packaged lady bugs?

It seems like this would be a good idea, but releasing packaged, field collected ladybugs has not been shown to provide long lasting protection. The chance of the “ladies” obediently staying where you want them is questionable. Further, field collected ladybugs can harbor a parasite which is a natural enemy of the ladybug population, according to CSU entomologists.

Want more information?

Check out the following CSU publications:

 

Written by Linda McDonnell, a Denver County Master Gardener

 

 

 

 

 

A Summer Garden Full of Drama

This year’s gardening season had enough drama to sell out a theatre. There were the performances that played out on the big screen, like waiting to see which trees and shrubs would bounce back from November’s flash-freeze. And there were the dailies, wondering if the wild weather would end the season before it even began. Instead of Splendor in the Grass, my garden was more like something from The Good, the Bad and the Ugly.

Ambush bugThis was the first summer I’d ever seen oddly shaped insects called ambush bugs on the brown-eyed Susan flowers. I didn’t know what they were when I first spotted them and had to do some research. These members of the assassin bug family have perfect yellow and brown camouflage that allows them to hide on plants and flowers. When an unsuspecting insect lands, they attack quickly and use their sharp pincers to hold the unfortunate while sucking the life right out of it. Ambush bugs (subfamily Phymatinae) land in the good bug category when striking and killing flies; the bad bug category when they happen upon a honey bee.

Funnel Web spiderI’ve seen many orb weaver spiders in my garden through the years, but this summer was the first time I had the chance to watch a funnel web weaver at work. I’m glad these spiders (Agelendiae) are some of the good guys. They capture their prey with a sheet-like web that features a tunnel retreat where they lie in wait for their prey. When a flying insect hits one of the barrier strands suspended above the tunnel, it falls into the sheet below. That’s when the spider dashes from inside the tunnel to drag its dinner inside.

Grasshopper hidingOne of the bad critters in my garden this year had a voracious appetite. Grasshoppers were practically everywhere in my garden, some hiding in plain sight. They gnawed on the long sedge leaves, feasted on flowers and tore through the beautiful foliage on my eggplants. Fortunately, they left the tomatoes and squash alone. Because I didn’t want to use insecticides or traps in my garden, I suffered through the worst of the invasion before their numbers started to dwindle.

Hollyhock weevilAnother bad bug appeared in my garden in the form of hollyhock weevils (Apion longirostre). These tiny insects enjoyed crawling up the tall hollyhock stalks and eating the leaves, seeds and buds of one of my favorite perennial flowers. These evil weevils use their long beaks for chewing into the flower buds so they can lay their eggs. Then the grubs feed on the seeds which can spell the end to hollyhocks in the future. I spent many enjoyable summer mornings picking these destructive pests off the plants and crushing them with my fingers. Damaged pods have to go, too.

squirrel damageThe ugly damage left behind by furry four-legged pests doesn’t bother me as much as having insects eat the garden. Squirrels are so entertaining that I don’t mind sharing a few cherry tomatoes or baby butternut squashes with them. I think it’s a fair trade for a front-seat at one of the best garden shows around.

By Jodi Torpey
Denver Master Gardener

Tomato Gardeners Need this App

Tomato MDOne of the best gardening investments I’ve made lately is buying the Tomato MD app available through the American Phytopathological Society. Master gardeners need this app, especially those who answer gardener’s questions at the farmers’ market, by phone or online.

The reasonable $2.99 price is worth every penny if you’ve ever been stumped by the question, “What’s wrong with my tomato plant?”

I don’t know about you, but tomato-growing questions are my most frequently asked question. It’s also a question that I’ve asked myself many times. The CSU fact sheet on Recognizing Tomato Problems is a good resource, but it’s less comprehensive than the Tomato MD app.

Tomato MD is an interactive resource that works with either Apple or Android devices. It’s easy to use and can help you pinpoint just about any tomato problem using the menu of plant diseases and insect problems.

The beauty of this app is that it can be used anytime, anywhere because you don’t need the Internet to access its features. Once you download it to your phone or tablet, you can take it with you into the garden or the CSU Master Gardener’s booth at farmers’ markets or any gardening event.

The app is a great resource for master gardeners. Home gardeners, garden center staff and even professional growers can benefit from this tomato-growing tool, too.

When you’re asked about a tomato issue, the app lets you search in three different ways:

Alphabetical listing of diseases and insects
Images of the 35 most common problems that affect tomato plants
Disease or insect damage characteristics

I’ve found it’s helpful to start by clicking on the photo gallery. That’s where you can choose the affected part of the plant, from leaf to flower, fruit, stem and roots. Select the affected area and then thumb through the images to find a photo match.

Tomato MD covers problems like alternaria stem canker, bacterial spot, blossom end rot, drought stress injury, tomato spotted wilt, early blight, late blight and plenty more. The rogue’s gallery of insects and mites includes tomato hornworms, tomato fruitworms, stink bugs and many of the other harmful insect pests.

Once you’ve identified the problem, the app gives you a menu of options for symptoms, causes and sources, other plant hosts, imitators, control options and additional help with diagnosis.

Much of the content for the Tomato MD app is from the American Phytopathological Society’s research and its two massive and expensive volumes called Tomato Health Management ($89) and Compendium of Tomato Diseases and Pests ($99). I’ve wanted to add these books to my library, but the cost was prohibitive.

At $2.99 Tomato MD solves that tomato problem, too.

By Jodi Torpey, a Denver Master Gardener

One Less Ash Tree for Emerald Ash Borers

yellow tree leaves
When I planted a white ash tree about 10 years ago, I never dreamed I’d be chopping it down while it was still healthy. But I did just that earlier this season and took the loppers to the tree while it was sending out new leaves.

I decided to take action now instead of waiting for the Emerald Ash Borer (EAB) to take it out one day in the future.

It wasn’t an easy decision. I liked this tree a lot, especially in the fall when the leaves turned a brilliant yellow. But it’s only a matter of time before the dreaded EAB makes its way into my landscape and forces my hand.

The tiny Emerald Ash Borer has already caused the death or decline of tens of millions of ash trees in at least 20 states and now it’s in Colorado.

I chose to remove the tree this season to avoid my limited options in the future. Like other ash-tree owners, I’d have to decide whether to budget for the expense of treating a taller tree with insecticides every one or two years to prevent EAB damage or wait for the borers to kill the tree slowly and then hire someone to remove it for me.

Now that this ash tree is gone, I can take my time and find another kind of tree to replace it.

Then I’ll be able to focus my preventive efforts on the much larger ash that shades most of the front yard. That tree is more valuable and will be worth the cost of treating it, once the time comes.

Right now, home owners and urban foresters in and around Boulder are trying to make the same kinds of decisions. They’re deciding whether to treat their trees with insecticides — while weighing the costs with the environmental hazards; measuring the effectiveness with ease of application.

If you have ash trees on your property, you’ll have to make similar decisions in the future, too. Now’s a good time to start thinking of what you’ll do once the EAB invades your landscape. Would you remove a healthy ash tree as a drastic measure to prevent EAB in the future?

There are some good resources to help you decide, including CSU’s Department of Bioagricultural Sciences and Pest Management website and the Colorado Department of Agriculture EAB website that includes an Ash Tree Zone interactive map and a way to sign up for the EAB newsletter to stay informed.

By Jodi Torpey
A Denver master gardener