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April Showers Might Bring May Flowers - But They Also Bring Bugs!

Bark Beetle damage to a tree
Bureau of Land Management
Bark Beetle damage to a tree

Finally we’re getting some moisture for the Front Range.  As everything starts to grow, the weeds and insects are busting out, too.


We were in a yard the other day that was infested with clover mites.  The pin-point, orange insects love it dry and warm.  Sometimes you’ll find a group of them on a south facing window.  The infestation we found was on columbine, iris, daffodils and tulips.  I’m sure the grass was crawling with the sucking insects.  They can decimate warm lawn areas.  Cooler, wet weather will slow down the mites.  Extra overhead water will help control them once it warms up again.

Timing sprays help control other insects that attack plants in the spring.  Every season is different.  The timing of insect flights determines when they should be controlled.  Tree care companies monitor these flights so sprays are applied at the right time for the season.

Mountain Pine Beetle will be moving around soon.  They emerge as adults in late spring.  They burrow into the tree to start laying eggs.  The larvae hatch and tunnel further under the tree bark.  There has been success in spraying trees during the adult emergence and egg laying.  The spray needs to be applied at the right time and in the right way.

Pine Tip Moth attacks the developing buds of pines.  They prefer Ponderosa Pine but they go after mugho and other pines.  The moth lays its eggs in late summer and the larvae spend the winter in a small cocoon on the tree.  They come out at the same time the new growth is starting to grow.  About a month later you notice the tips of the tree and branches are dead and dry.   This insect can disfigure a tree.  Sprays for this insect should be timed for pine bud break in May. 

The past couple of years Pinyon Pine have been brutalized by Pinyon Tip Moth.  The damage isn’t noticeable until the new growth turns brown and drupes.  The larvae tunnels into the new growth as it elongates.  You may see sap or sawdust frass at the base of the new growth.  This insect can be controlled with sprays timed when it is active.  Usually late April and May are the best control times. 

Follow the direction on the label of any spray used to control insects.  Larger trees need special equipment to apply sprays.  Tree care companies have the expertise to apply insect controls safely and at the right time. 


Tom has been offering garden advice on KUNC for almost two decades. During that time he has been the wholesale sales manager at Ft. Collins Nursery, Inc. Since January of 2005 he has been the owner and operator of Throgmorton Plant Management, LLC., a landscape installation and maintenance company as well as a horticultural consulting firm. He lives in northern Ft. Collins with his wife and two kids.