Welcome to our Ag Blog. Our field scouts will offer a unique ground-level perspective from the field to you as an independent field scout with the San Joaquin Sustainable Farming Project. Our mission is to promote sustainable farming systems throughout the Central Valley and provide you with the latest information about cotton, almond and alfalfa crops. From time to time, you'll also find guest posts from our project team and other contributors. This Blog is edited by Gilbert Mohtes-Chan.
Monday, July 7, 2014
Sweeping Fields Tracks Pest Populations and Protects Crops
More worms are showing up in alfalfa fields. Lygus
bugs are turning up more often in cotton fields.
track of the number of bad bugs and good bugs that are making a home in your
cotton and alfalfa fields is quite important as summer heats up. Pest
populations can suddenly explode and gobble away at your harvest time profits.
“Pest populations are growing. They can grow pretty
fast,” says field scout Carlos Silva.
Carlos uses his sweep net to check on pests in an alfalfa field.
Each week, Carlos heads into the blistering heat to
survey pest populations in cotton and alfalfa fields across the San Joaquin
Valley. His scouting provides a second set of eyes for growers, supplementing
information gathered by their pest control advisors and the farmers themselves.
A close-up of alfalfa weevils in his sweep net.
tool of the trade is a sweep net – a kind of oversized butterfly net. Carlos
will pick three locations in a field and use tennis-like forehand and backhand
moves and counting the number of passes as the net snags collect bugs hiding in
the fields. “Take time to look at the net,” he says about carefully inspecting
the pest haul.
certain art and science about using a sweep net. The effectiveness of this
sampling practice hinges on how the net is used. Following standard practices
ensures results from different people are comparable.
Here’s a refresher course covering alfalfa and
Sweep the field when the plants are at least 6- to 10-inches tall. Swing the
net in a 180-degree arc so the net’s rim hits the top 6 to 8 inches. Hold the
net less than vertical to ensure the bottom edge hits the alfalfa first. Many
people will sweep from right to left, and then take a step and sweep again left
to right. After 5 sweeps, pull the net through the air to push the bugs into
the bottom of the net bag. UC IPM recommends taking a sample in four different
spots in the field.
If it’s difficult to count the bugs in the field,
place the insects in a bag and cool the contents to slow done pest
movement.UC IPM provides information
about treatment thresholds for various pests.
Cotton: Start to sweep for lygus at first cotton plant square, taking samples
twice a week in the field. UC IPM recommends sampling each quarter of a field
and taking even more samples in fields larger than 8 acres. Do 50 sweeps across
one row of cotton to sample for lygus, making sure the sweeps don’t overlap.
Lygus monitoring can end when acala plants have 5 nodes above white flower and
Pima has 3.5.