Cotton growers are finishing the first crop irrigation. |
Cotton season is in full swing with growers now wrapping up
the first irrigation. The watering, mixed in with fertilizer folded into the
soil earlier, are now combining to help these plants thrive and develop lots of
fruit.
I’m spotting the first pinhead squares at the fifth to sixth
node. That’s a good sign because normally you find the first pinheads
developing at the sixth to seventh nodes. This means the plants could develop
more fiber-bearing fruit, likely translating into a higher yield at harvest
time.
At this plant development stage, growers now need to be more
vigilant about monitoring for pests, especially lygus, the bane of all cotton
growers. Lygus can damage squares at all stages of development. It’s important
to monitor for this pest to keep the first crop.
Lygus can be trouble. - UC IPM photo |
In this high-tech age, the most effective way to monitor for
lygus is the old-fashion way – using a sweep net.
Here’s the field
scout’s short course on sweep net sampling: Pick three or four different locations
of the cotton field to perform the sweeps. Picture a big “X” overlaid on top of
your field and take your pest samples at each leg of the X. This ensures your
locations are equally spaces out to give you a good overview or sample from
your entire acreage. You also can follow a “V” pattern.
Net sampling should be done weekly. Also be
sure to rotate the sample locations to ensure you cover all areas of the field.
The technique is pretty straight forward. As you walk down a row, you move in a sweeping motion back
and forth or right to left (left to right if you’re a lefty). Image the sweep
net as a tennis racket. One sweep is a forehand move and the second sweep is a
backhand motion – Spanish tennis superstar Rafael Nadal would be proud. In each
location, you want to do 50 sweeps.
Check the UC IPM online for lygus monitoring for
cotton for more information about sweep net sampling and pesticide
treatment thresholds. I can’t stress it enough, now this is the time to be
vigilant about regular pest monitoring in the field. Spending time and labor on
this task, saves time and money in the long run by reducing chemical inputs and
costs as well as increasing yields.
It's important to monitor for pests with a sweep net. - UC IPM photo |
This also is the time to do plant mapping. While I tell
growers a plant can hold only so much fruit, the idea is to achieve the ideal
maximum amount of fruit. Mapping isn’t an exercise in cartography – the art of
making maps. The real world application is simple: Mapping lets you track the
plant’s growth and development throughout the season and plays an important
role in treatment and management decisions. Again, here’s a UC link to learn
more about cotton
plant mapping.
Right now, some growers may want to use growth regulators to
slow vegetative growth and set more fruit. However, I suggest growers not jump
the gun on this. With the first irrigation taking place and fertilizer already
feeding the plants, cotton plants are getting food to grow. Applying growth
regulators at this same time would seem counterproductive.
This also is a good time to take plant tissue samples. By
analyzing the tissue, you can get a read on the level of nitrogen, or
fertilizer, in the plant and decide if the plant is getting too much nutrients
or not enough. I’ll speak more on this topic in my next blog.
Fusarium wilt is more evident in fields. |
On the plant disease front, I am seeing quite a bit of
evidence of fusarium wilt damage. It’s the most I’ve seen in the past couple of
years. Weather may be a factor causing this problem. I would check in with
Fresno County’s UC Cooperative Extension cotton specialist Dan Munk about any
concerns in your field.
Looking at alfalfa, growers are finished with the second
cutting and now moving onto irrigating again and applying nitrogen to feed
their crop. I’m spotting a light amount of worms and an uptick in lygus.
So
far, growers are doing a good job of leaving uncut strips of alfalfa to prevent
lygus from migrating to nearby cotton fields. It hasn’t reached the point yet
where growers need to treat their alfalfa. Natural predators seem to be keeping
crop-damaging pests in check at the moment. Again pest monitoring remains
important here as well.
Cotton Field Day:
Remember Tuesday’s event (June 12) will be from 10 a.m. to noon at the Housley
and Vandenberg Farm on Sierra Avenue in Firebaugh. We will feature UC IPM
advisor Dr. Pete Goodell and farm advisor Dan Munk. They will offer valuable tips for early season pest and
agronomic management. Directions are
available in the events section of the Sustainable Cotton Project’s website – www.sustainablecotton.org. One and a
half hours of continuing education credits have been approved. It will be worth
your time to get your questions answered directly from these UC experts. I will
see you there.
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