Exercise 7: Inoculum Reduction with Certified Seed
Many potato farmers save a part of their harvested crop to use as seed for the following season. This
practice carries with it the risk of planting seed pieces from infected tubers. Certified seed producers
use far more stringent measures of protection, inspection, and roguing than table stock producers could
afford, and as a result their seed is likely to have a far lower incidence of infected tubers.
To show the effect of certified seed, let us first assume that all the inoculum comes from infected seed.
In the Inoculum menu, select Sporangia..., and set "maximum sporangia per day" for both
the cull pile and the unsprayed field to zero. Then select Infections... in the Inoculum
menu and enter 100 infections per hectare to represent uncertified seed saved from the previous
crop. Compare the results with those from a simulation with only 1 infection per hectare to
represent certified seed. If certified seed cost you double what you would pay to plant your own seed
($.22/kg versus $.11/kg, adding $313/hectare to your production costs), would you plant your own seed or
certified seed? (Explain your rationale.)
....proceed to EXERCISE 8
....return to Introduction
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