And a Y=A(1−e ^-BX) to You Too!

In the year 1997, I successfully used the Mitscherlich curve in deriving the economic
injury level of stable flies on feeder cattle for my Ph.D. dissertation down there one state
below:

Catangui, M.A., J. B. Campbell, G. D. Thomas, and D. J. Boxler.  1997.  Calculating
                economic injury levels for stable flies (Diptera: Muscidae) on feeder heifers.
                Journal of Economic Entomology 90: 6-10 (Forum).

Mitscherlich, E. A.  1912.  Zum gesetz vom minimum.  Eine antwort an th. Pfeiffer und seine
                mitarbeiter.  Landw. Vers. Sta. 77:  413-418.

Little did I know that I will use it again to derive the economic injury level of the soybean
aphid on soybeans in 2005.  Can I have a hep-hep?  Thank you Buford.

To me the Mitscherlich has a lot of biological relevance wherein a response approaches
a maximum asymptotically.  Kinda maximum possible something that is never exceeded.
Por ejemplo, even though soybean aphids are quite injurious, the soybean plant will still
yield something, albeit much lower than if the aphids were not present.

Our data do indicate that the MPR caused by soybean aphids may be 80%.  Soybean
plant breeders and seed companies can attempt to reduce this current MPR to select
for more tolerant soybean varieties.

You heard it here first, the concept of a "maximum possible reduction" (MPR) in crop
yields caused by insect pests.  I am of the opinion that the Mitscherlich curve will be one
of the most important tools in deriving economic injury levels for many different pests of
crops and livestock in the future.

There you have it folks, the Mitscherlich strikes again.  We also used both the logistic
and the normal curves to track soybean aphid growth over Julian dates.  Eric will have
them in his publication if he ever finishes his thesis.

Mitscherlich.  Logistic.  Normal.  Beautiful.  Bottom line is that we have thresholds.


                              

The  logistic curve also proved to be very useful because it has an inflection point that
indicated the time (date) when them aphids were multiplying the fastest.  "But obviously,
not to mention the variable A which represents the carrying capacity of the soybean plants,"
according to Buford who told me that the formula of the logistic curve is Y=[A]÷[1+e^(B-CX)].

There goes Buford again with his fancy mathematical formula . . . .


Brand New! Stage specific economic injury levels for V5, R2, R4, and R5

                                      

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 Web Posted on Tuesday, June 14, 2005 by Mike Catangui.  Last Updated on Tuesday, June 28, 2005.