When do borers hatch?
- To: Multiple recipients of list <i*@rt66.com>
- Subject: When do borers hatch?
- From: C* M* <c*@tiac.net>
- Date: Tue, 4 Mar 1997 09:53:27 -0700 (MST)
Clarence wrote:
>
>I usually spray once---at most twice. The only time it has not worked has
>been when I could not get out to spray it on when we had a very early
>spring---it is, after all, the weather that determines when the borers hatch.
> They are intelligent, 'tis true. But they have not yet been able to tell
>what date is on the calendar. Clarence Mahan in VA
>
>
In 1993 the University of Massachusetts's Garden Calendar explored the idea
of "Growing Degree Days" as markers for insect emergence. The idea was to
average the high and low temperature of a day. You then kept an accumulated
seasonal total of the amount by which that average exceeded 50 degrees, ie
((H+L)/2)-50. (If the figure was negative you did not add it to the
accumulating total.) The theory: "most insects and mites, as well as weeds
and diseases, have generally predictable life cycles that depend on
temperature, or more accurately, the accumulation of heat." In other words,
different types of pests emerge when the accumulated degree days hit a
species-specific figure. I've not read anything else about that research,
but it might be an interesting approach for iris growers to pursue. It
would take several years to come to any conclusions, but....
---------
Kathy Marble <cmarble@tiac.net>
Harvard, MA
zone 5
