|
<br />.
<br />.
<br /> >....,-~..,~
<br /> ..-... -'~",,_.
<br />Topics i
<br />, -
<br /> ,
<br /> -
<br />~~ardening .
<br /> <
<br /> : Two-lined chestnut borer poses
<br /> - risk to oaks ,weakened by drought
<br /> -
<br /> -
<br /> -,
<br /> -
<br /> ,
<br /> : By Jeff Hahn in late summer, the tree's health. The best time to
<br /> fertilize is in the fall after the tree
<br /> . The 1988 drought greatly weak- Two-lined chestnut borers first has gone dormant or in the
<br /> , ened and stressed many of our attack the tree's crown, so the spring,
<br /> ~ landscape trees, causing them to tree dies from the top, If the bark
<br /> : be more vulnerable to insect and is removedtrom dead limbs, tar- Prune dead limbs that are infest-
<br /> , disease problems, Oaks are no val tunnels can be seen, The D- ed with this borer two teet into
<br /> ; exception; they may be killed by shaped exit holes also may be healthy wood to ensure the borer
<br /> . the two-lined chestnut borer, noticed. is removed. Trees killed by this
<br /> . insect also should be removed,
<br /> . In Minnesota, two-lined chestnut The dieback symptoms may be
<br /> - borers attack most oaks, includ- confused with oak wilt. Red oaks It is not necessary to do anything
<br /> . ing red oaks, white oaks and bur are most susceptible to oak wilt special with oak firewood to pre-
<br /> oaks, as well as ironwood trees. while white and bur oaks are vent beetles from emerging,
<br /> - They prefer unhealthy trees and more resistant. The'only sure way While. debarking the wood in Au-
<br /> : do not kill vigorous ones. Be,sides to correctly distinguish oak wilt is gust or covering the wood pile
<br /> drought stress, trees can be to have it tested at a diagnostic trom May through July helps re-
<br /> weakened by construction dam- lab, e.g, at the state shade tree dUGe the number of surviving
<br /> < age to roots, diseases and se- lab. beetles, this is unlikely to change
<br /> . vere insect defoliation. the fate of nearby oaks as long as
<br /> Chestnut borers can be tatat to two-lined chestnut borers are
<br /> . Adult beetles emerge from wood trees, However, if the problem is common, Unhealthy trees still will
<br /> in late May through July, causing identified early, corrective meas- be attacked and healthy ones will
<br /> . characteristic D-shaped holes, ures can be taken. be immune. .
<br /> : They are slender, dark-colored
<br /> - beetles with two yellowish The tree's health is important. Insecticides usually are not sug-
<br /> - stripes. On the bark females lay Many areas of the state are re- gested; they will not prevent
<br /> : eggs that hatch into worm-like ceiving normal precipitation, and these borers trom attacking and
<br /> - larvae, These larvae bore through oaks, which are hardy, native killing trees as long as they re-
<br /> . the bark into the wood, Their me- trees, may recover naturally on main weakened, The tree's health
<br /> : andering tunhels girdle the tree, their own, Supplemental watering in the end is the deciding factor.
<br /> - cutting off the flow of water and when it remains dry also may be Jeff Hahn is an entomologist with.the
<br /> :. nutrients from the roots to the necessary,
<br /> : foliage, This results ifl branch die. Dial U Insect and Plant Information
<br /> : back, which is often first noticed Fertilizing also can help improve Clinic, Minnesota Extension Service.
<br /> '"
<br /> ----
<br />
|