From Kerry Siders for Texas AA&M AgriLife Extension
Again, we have been through the wringer the last several weeks. My prayer now is that we have good open weather from here on out with gentle, timely rains, and a great long fall. On the bright side we have good soil moisture for mid-July and the temperatures are generating good heat units.
Based on the IPM scouting program fields here is what the average upland cotton plant looks like:
Average number of total nodes is 13 (range 6 to 16)
1st fruiting branch at node 7 (range 5-9)
Square retention of 1st positions is 91% (range 67-100%)
Node length is 0.9″ (range of 0.4″-1.8″)
Plant populations average 32,650 per acre (range 17,300 to 48,000)
Nodes above white flower 9 (currently only one field has just started)
I began finding blooms this morning Friday, July 16. I project we should go into bloom with 8.5 nodes above white bloom. This places first bloom on some early fields which have escaped much damage near July 24, with
remaining fields hitting first bloom after this date. Just recall that August 20 is the date when we can say with some confidence that a boll formed on that day will have time to mature out. Anything formed after that point the odds of it having time to mature out decrease greatly. It remains very quiet currently on the cotton insect front. I would really watch fleahoppers and Lygus on this late cotton that is squaring up.
My priority list for this upcoming week:
- Keep close watch fleahoppers and Lygus on young squaring cotton.
- Stay on top of weed control, cultivate, hoe, whatever it takes to keep the pigweed from going to seed. It is a numbers game.
- If you still have fertilizer to go out let us get it in place before the end of this month. This applies even to late cotton. Late fertilizer applications will only delay maturity and can encourage cotton aphids.
- Look at the top 3-4 nodes on your cotton if the internode length is longer than 1.5″ consider a plant growth regulator. Call and we can visit more about this.
Peanuts are flowering strong, and peg/pod development is very good as well. The humid moist environment we have had is very conducive for this growth and development process. It can also make it ripe for disease development from this point forward. Scout fields closely and anticipate disease issues.
Lygus Bugs on Cotton
The western tarnished plant bug (Lygus hesperus Knight) is one of several Lygus species that feeds on cotton terminals, squares, and small bolls. Adults are 1/4-inch-long, have a conspicuous triangle in the center of the back, are winged, and vary in color from pale green to yellowish brown with reddish brown to black
markings. Immature lygus bugs are called nymphs. They are uniformly pale green with red-tipped antennae; late instars have four conspicuous black spots on the thorax and one large black spot near the base of the abdomen. The nymph’s wings are not developed, but nymphs can move rapidly and are difficult to detect in cotton foliage. Small nymphs may be confused with aphids, cotton fleahoppers and leaf hopper nymphs. Plant bugs prefer legumes to cotton and usually are found in large numbers in areas of alfalfa or potato production or areas providing wild hosts such as clovers, vetches, mustard, and dock. Lygus bugs are attracted to succulent growth, their feeding results in shedding of squares and small bolls, stunted growth, and boll
deformation. Feeding damage to small bolls is often characterized as small black spots or small, sunken
lesions. The feeding that causes these spots or lesions may or may not penetrate the boll wall and damage
developing seeds or lint. Damage to blooms appears as black anthers and puckered areas in petals.
Management and decision making. The need for lygus bug control is determined by their abundance in
relation to the fruiting condition of the cotton plants. Fields should be inspected for lygus bugs at 4- to 5-day
intervals using a drop cloth.
During the first week of squaring, the economic threshold is one lygus bug adult or nymph per 3 feet
of row combined with less than 90 percent square set. In the second week of squaring, the economic
threshold is one lygus bug adult or nymph per 3 feet of row combined with less than 85 percent
square set. In the third week of squaring, the economic threshold is one lygus bug adult or nymph
per 3 feet of row combined with less than 75 percent square set. After the third week of squaring, the
economic threshold is two lygus bug adults or nymphs per 3 feet of row with less than acceptable
fruit retention. After peak bloom, begin treatment when drop cloth counts exceed two lygus bug
adults or nymphs per 3 feet of row and plants have failed to retain squares and set bolls normally
during the first 4 to 5 weeks of fruiting.