Agriculture Reference
In-Depth Information
Case 2: Watching the Weather to Reduce Pesticide Use
The vegetable industry in the Salinas Valley has something of a reputation
for very intensive use of several pesticides in a single application, in order
to control multiple kinds of pests. Colloquially, this practice of mixing
pesticides is called the Salinas Cocktail. Although, by law, growers need to
have the recommendation of a Pest Control Advisor (PCA)
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for use of a
given chemical on a given crop, the actual application of pesticides often
follows a program approach, as in the case of fertilizers, applied through
a commercial pest management service. Therefore, the use of pesticides is
also often treated as a kind of insurance, which can lead to overapplication
and the possibility of pest resistance.
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The case I draw on here was a collaborative effort to control downy
mildew (DM), an important disease of lettuce and other leafy vegetable
crops, while reducing pesticide use. As with nitrate management, an
improved management regime is one alternative to an outright ban on
pesticides used for DM. DM is a foliar (leaf-based) disease most prevalent
in cooler, more humid coastal vegetable-growing areas. This is in contrast
to drier growing areas, in Southern California and Arizona, where vegeta-
bles are grown during the winter months. In these desert regions, DM
is never a problem. Even within the coastal growing areas, however, the
incidence of DM can be quite variable; sometimes the disease is rare and
can be controlled, while at other times it is in every fi eld and does great
damage. Therefore, a program approach, when used to control DM, can
be wasteful because this method sprays for the disease whether the risk is
small or large.
In contrast to the relatively low-tech quick test system, a group of uni-
versity researchers (including the plant pathology advisor), the Lettuce
Board, and equipment manufacturers were, at the time of my research,
working on a rather high-tech solution for managing DM (and the chemi-
cals used to treat it) on lettuce. The solution involved the use of electronic
weather stations placed throughout the vegetable-growing areas of the
county. These weather stations monitored climatic conditions in their
vicinity and radioed these data to a central computer system that processed
them using a special DM algorithm, a model developed to predict, based
on climatic factors, when DM was likely to be a problem on lettuce. This
method of predicting DM would then allow growers to fi ne-tune their
