Dial-a-Garden Message

for the Week of Monday, August 10, 2009

Susan Rose, Horticulture Education Specialist
Colorado State University Extension Tri River Area

Thank you for calling Dial-a-Garden. This message was recorded on Tuesday, August 11, 2009.

The evapotranspiration rate for the last week is 1.67 inches of water, for cool-season grasses (Kentucky bluegrass, perennial ryegrass, tall fescue) in the Grand Valley. Water no more frequently than three times a week. Research done at our office several years ago indicates that you can cut the ET figure by as much as half, and still have great looking bluegrass. The less often you can water the lawn at this time, the fewer disease problems you will have.

Ants are present in the landscape in amazingly large numbers. Unless they migrate into the house or in other ways are a nuisance, they should be regarded as a beneficial insect. They help manage insects and weed seeds, and aerate the soil. The winged form is the mating form, which often occurs in large numbers but only for a short time. Following the mating flight, the fertilized queen will begin a new colony. Ants coming into the home should be identified before treatments are applied, as in some cases treating the ants can stimulate the formation of new colonies. Bring a sample to the Extension office for identification. Ants can be distinguished from termites by the very narrow waist. Please see the CSU web site at www.ext.colostate.edu/pubs/insect/05518.html for additional information and helpful illustrations.

The tamarisk leaf beetle, Diorhabda elongata, has made its way into the valley where it is hard at work. A fact sheet at www.tamariskcoalition.org/tamariskcoalition/BioControl.html gives an overview of this insect and what we can expect from it. It has been very thoroughly tested and will not harm native plants; once it has defoliated a tamarisk it moves on to another one. Tamarisk plants may take up to five years to succumb to beetle feeding. When the host numbers are significantly reduced, the beetle population will decline as well.

Wasps are active in large numbers right now. Several kinds of wasps can be found in our area, but the most common is the European paper wasp. This insect can become quite aggressive if threatened but is fairly docile otherwise. To control wasps, approach the nests at night or in the early morning, when the insects are less active. A quick knockdown wasp spray is recommended; this should be followed up by destroying the nest and cleaning the site if possible. European paper wasps will reuse the same nest or rebuild in the same site if it is left untreated. Please see our fact sheet number 5.525 on Nuisance Wasps and Bees at www.ext.colostate.edu/pubs/insect/05525.html or give the Master Gardeners a call at 244-1836 to receive a copy.

Powdery mildew is one of the most common plant diseases in our area. It is one of the very few fungi that doesn’t require the presence of water, but it does need high humidity. Typically, we see a great deal of this disease in late summer and early fall, as the evenings get a little cooler and the humidity increases. Powdery mildew is worse in areas that are shady or have poor air circulation; some control can often be achieved by selective thinning to reduce the humidity around the plant. Powdery mildew attacks many different species of plants, but it is fairly host-specific and will not spread, for example, from roses to lawns. Severe infections may merit treatments with fungicides, but if the humidity remains high the problem is likely to recur.

We will begin docent training next month for the Ute Ethno-Botany Learning Garden. This newest addition to the Arboretum features native plants used by the Utes that grow at many different elevations in Colorado. Our docents will learn about the plants, their uses, and the seasonal migration pattern of the Utes. Tours will be arranged for 2nd graders, 4th graders, and adults. For more information please contact me at susan.rose@colostate.edu or 244-1841.

You can reach a Master Gardener in Montrose at 249-3935, in Delta at 874-2195, and in Mesa County at 244-1836. If we’re away from our desk, please leave a message and we’ll get back to you.

Thank you for calling Dial-a-Garden. This message will be updated next week; have a great week!