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 produced by Gilbert Mohtes-Chan.
Monday, June 11, 2018
The Heat is on to Monitor for Lygus in Valley Cotton Fields
With more hot weather predicted in the
Valley this week, it’s a sure bet that cotton plants will flourish. And so will
“Cotton likes hot weather. I wouldn’t
be surprised if cotton plants grow three inches in a week,” field scout Damien
Jelen says, noting the return of triple digit temperatures over the next few
days in the Valley. Last week, the Valley recorded two days of 100-degree
spring weather. Forecasters are predicting more sizzling weather Tuesday and
Wednesday – good cotton growing weather you might say.
A cotton square is damaged by lygus bugs.
Of course, there’s a flip side to the
pre-summer heat and it’s lurking in the hay ready to explode in numbers. That’s
“I’m starting to see lygus in cotton,” Damien says. His
observation raises the red flag because cotton is in the vulnerable time of
development – the early squaring period. The square is part of the developing
cotton plant and becomes the flower that eventually turns
Lygus can threaten cotton until the
final boll set in the summer. The pest pierces the square and damages the
tissue. Smaller squares can shrivel and drop from the plant. Larger ones may
not fertilize. If too many squares drop, the cotton plant may experience too
much vegetative growth, resulting in tall, spindly plants and reduce yields,
according to UC Integrated Pest Management.
Lygus populations will increase
steadily through the end of this month.To monitor the pest in cotton, Damien and other scouts will take a sweep
net and canvass the field. The thresholds for growers to consider treatment are
low this time of year – one bug for every 50 passes of the sweep net through
mid-June and two per 50 from June 15 to 30, UC IPM says.
Lygus bugs prefer to live in alfalfa fields rather than in cotton.
Cotton isn’t the first choice as a home for lygus. The bug
actually prefers to live in crops such as alfalfa, safflower, beans, potatoes
and tomatoes. “As these crops are prepared for harvest, winged adults
migrate out of the field in search of new hosts. Careful management of these
crops can reduce the migration of lygus bugs into cotton fields during cotton's
most vulnerable period: mid-May through late July. Watch closely cotton fields
that are downwind from these crops by sampling the cotton and surrounding
fields often,” UC IPM says.
Around the Valley, it’s common to find alfalfa growing close
to cotton fields.Moreover, alfalfa is
harvested almost monthly, meaning lygus populations will flock to find new
homes in nearby cotton fields.
One way to keep lygus in alfalfa is to leave small sections
of the field uncut during harvest.This
will leave a habitat for lygus and keep the pest from migrating into
neighboring cotton fields. We’ll talk more about this practice in the future.
“I haven’t seen much strip cutting so far,” Damien says.
With more high temperatures coming up, “I’m going to get high lygus counts.”