CO-Horts Blog

Thursday, August 4, 2022

Chrysanthemum lace bugs

 By Irene Shonle, El Paso County Horticulture

This year, I have an outbreak of chrysanthemum lace bugs on many different species of plants within the sunflower family in my garden, including annual sunflowers, tansy aster, rabbitbrush, goldenrods and Maximilian sunflowers. Interestingly, they don’t seem to be attacking the showy goldeneye or the threadleaf ragwort.

Chrysanthemum lace bug damage on sunflower

Chrysanthemum lace bug damage on rabbitbrush

Chrysanthemum lace bug damage on tansy aster - note how bleached the leaves are in comparison to the green penstemon below it

There are many species of lacebugs out there, and they range from 1/8 inch to 1/3 inch long. The nymph stages are wingless and are darker than the adults.  Adults are light colored, and actually quite interesting looking if you look close up – the “lace” in their name becomes obvious.   It takes about 30 days to go from egg to adult, and there can be multiple generations per year.

Chrysanthemum lace bugs - they are usually on the undersides of leaves, but can also be found on the upper sides.

Lace bugs feed primarily on leaf undersides. They have piercing-sucking mouthparts that puncture individual leaf cells, and this is what causes the bleaching. The damage associated with lace bugs is similar to that caused by spider mites and leafhoppers, but a tell-tale difference is that lace bugs leave black, tar-spot-like droppings on the leaves.

Usually, I don’t worry too much when I see aphids or lacebugs, because they typically don’t affect plant health and there are often natural enemies that can help control them – such as assassin bugs, lady beetles, green lacewings birds, and other predators.

However, in the last couple of weeks, the lace bug situation suddenly reached critical mass and I started noticing dramatically discolored leaves – the leaves turned straw colored within a couple of days or have large brown blotches.  Some smaller sunflowers were outright killed due to the infestations.  How quickly it went from being a minor nuisance to a pretty serious problem!

Chrysanthemum lace bugs bleaching out Maximilian sunflower

So, I have begun spraying the leaves with water to knock off the nymph stage, and picking off leaves with egg masses in an effort to reduce the population.  I take some comfort in knowing that population levels and damage varies widely from year to year, but will also monitor the situation more closely next spring and knock back any incipient populations just to avoid a repeat.  If need be, I’ll use some insecticidal soap or a horticultural oil, and spray it on the underside of the leaves. While broad-spectrum pesticides can be effective, I will avoid them, as they will also kill natural enemies


Tuesday, August 2, 2022

Ribbons and Livestock and Gardens, oh my!


It’s that time of year when, across the entire state, counties are gearing up for their county fairs. Event planning is being finalized, award ribbons are being made, and livestock is being meticulously groomed before show. Similarly, demonstration gardens are also being polished up before fair, but rather than being trimmed and brushed, gardens are being weeded and prepped.

Demonstration gardens are common features of extension offices, showcasing research-based practices for landscaping and/or gardening and often dedicated to a particular theme. For instance, many counties offer demonstration gardens that focus on native plants or on xeriscape gardening. Some counties have more uniquely-themed demonstration gardens, such as the Rock and Hell Strip Demonstration Garden in Boulder County or the Ute Ethno-botanical Learning Garden in the Tri-River area. So whether you’re interested in some ideas for your own landscaping or gardening project or you just want to tour some pretty gardens, make sure to check out your local demonstration gardens while you attend this year’s county fair (or anytime, really)!

Rock and Hell Strip Demonstration Garden in Boulder County

Ute Ethno-botanical Learning Garden in the Tri-River Area

Over at Jefferson County, we’ll be hosting an Open Garden Day on August 6th from 9 AM to 7 PM, located at the Jefferson County Fairgrounds in Golden. Demonstration gardens on-site include the Giving Farm Horticulture Garden, the Plant Select Garden, the Native Garden, and the Fruit Tree Orchard. Aside from having Master Gardeners available to answer any questions, we’ll be offering giveaways and garden-themed kids’ projects, so don’t miss out!

Giving Farm Horticulture Demonstration Garden in Jefferson County