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Depending on phenological stage of tree
development, several questions are asked to determine the presence and severity of insect
and mite pests and the mite predator, Stethorus punctum (LeConte). PSAOC queries the
profile to determine the present phenological stage. From this information a list of
insects and mites that can be a problem at that time of the season is constructed.
Pertinent questions are asked about each member of the list to determine if that species
is over the action threshold and must be treated. Some of these questions are posed to the
user and some to the profile. As a result of this inquiry an array of the insect and mite
species over the action threshold is passed along to the chemical management module.
For instance, one species, the European red mite, Panonychus ulmi (Koch), uses the
following information, phenological stage of tree development, age of tree, projected crop
load at harvest, rainfall history, number of mites per leaf, and number of Stethorus per 3
minute count. These pieces of information are used to measure the potential for a given
mite population to damage the tree in terms of yield, quality and return bloom in
subsequent years. The impact of the mite, being an indirect pest (not feeding directly on
the fruit), must be measured as an interaction with the tree's physiological functions.
Moveover, counts of the predator beetle Stethorus punctum, a commercially reliable
biological control for mites in Pennsylvania, are asked for. In many situations, there
will be enough beetles present to keep the mites from crossing the action threshold.
However, if after consideration of all of these variables mites are still projected to be
over threshold then this information is passed along to the chemical management module. |
