Thursday, June 4, 2015

Insect Alert

By Linda Langelo, CSU Horticulture Program Associate

According to our statewide pestlist serve and our CSU Entomologist, Whitney Cranshaw, here are the Elm tree insects to be aware of as we go from spring to summer.  Elms have taken a serious blow from the November cold snap and then again from the spring freeze.  As we go into the growing season these insects could devastate the elms.  There are a significant number throughout the eastern plains that have sustained the heaviest winter damage along with many other tree species.

The European elm flea weevil spends its winter nearby previously infested elm trees.  The adults mate in May and the females lay their eggs in larger veins of new leaves.  Once the eggs hatch, the larvae tunnel through the leaf and feed.  They produce a serpentine mine that gradually enlarges in diameter as the insect ages.  The mines terminate at the leaf edge where they remain and produce a blotchy area of mined tissue.  They will pupate in the mine and emerge in late May and June.  Then the adults feed on the undersides of leaves producing shothole injuries to the leaf interior.  This makes the leaves look lacy.  The adults are present through early August, and then they move to find sheltering cover for winter.   For further information and pictures, please go to this link on-line: http://bspm.agsci.colostate.edu/files/2013/03/European-Elm-Flea-Weevil.pdf

The Elm Leafminer spends its winter as full-grown larvae within a cocoon in the soil nearby a previously infested elm tree.  They pupate in late winter and are prepared to enter newly emerging leaves.   The females insert their eggs in the upper surface in the center of leaves.  As the larvae develop they produce leafmines that become blotchy.  Within three to four weeks the larvae cut through the bottom of the leaf and drop to the ground.  They are going to the soil to spin a cocoon.  For further information and pictures, please go to this link on-line: http://bspm.agsci.colostate.edu/files/2013/03/Elm-Leafminer.pdf

Sumac flea beetles the overwintering adult beetles will attack the sumac as the buds break.  They feed on the emerging leaves.  The females lay eggs in small masses on the twigs.  The larvae will emerge late May and early June feeding on the newly emerged leaves and may heavily defoliate plants. Adults emerge by early summer and may return to feed on leaves through September.  For further information and pictures, please go to this link on-line: http://www.ext.colostate.edu/pubs/insect/05592.html


For more information visit www.ext.colostate.edu

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