Editor’s note: Get Growing, written by the La Plata County Extension Office’s Master Gardener Program, appears every other week during the growing season. It features timely tips and suggestions for your garden and landscape.
By Darrin Parmenter
Depending on what you believe – insect activity this spring or climate forecasts from the National Weather Service – the summer of 2014 could be a really dry one.
Or a really wet one.
During the last couple of months, there have been numerous reports of increased levels of ips (aka “engraver” or “bark”) beetles throughout Southwest Colorado. We also have seen army cutworm populations, especially in the southwest corner of the county, explode this late winter and spring.
The insect, which has one generation per year, can be found under the soil during the day feeding on tender roots and above ground at night feeding on the rapidly growing leaves of many of our grass species. Area wheat and grass producers have seen fields decimated in a relatively short time. Typically, insecticides can be one of the few options for control, and unfortunately, much of that had to be done before now.
Anecdotally, the last time we saw army cutworm damage was in 2003.
Ips beetles damage pine and spruce trees, developing under the bark of trees and producing feeding tunnels that can cause dieback or death of trees. In our area, we have seen ips affect ponderosa and piñon pine as well as our local spruce trees. When trees get stressed (think drought), beetle populations can build and become a considerable threat to living trees.
Symptoms of ips beetle injury include a yellowish or reddish-brown boring dust that accumulates in bark crevices; affected parts of the tree can discolor and die (frequently we could see a single branch or the top of the tree die before other parts); and the presence of small round holes in the bark of infested trees. These holes indicate the beetles have completed their larva-to-adult development in the tree and have exited.
Prevention of ips beetle is best with an integrated approach. Promoting vigorous tree growth – adequate water (which may be difficult) and minimizing compaction and potential root damage – will help with the tree’s defense system. Freshly cut material from pruning, thinning or wildfire mitigation should be removed from the vicinity of valuable trees. And lastly, in order to protect valuable trees that have not been infested, a well-timed application of insecticide may be needed. It is generally recommended that a licensed and certified arborist or pesticide applicator perform this task.
And for those of you with a short memory or who were not in the area, the last time we saw elevated levels of ips beetles was the severe drought year of 2003.
parmenterdm@co.laplata.co.us or 382-6464. Darrin Parmenter is director and horticulture agent of the La Plata County Extension Office.
