Rainfall, clouds, and temperature have been quite a roller coaster in the back end of May and throughout June. We entered the early weeks anticipating drought and high temperatures, but weren't reached for more than a short sustained period. With only a couple cooler than average nights, temperatures have been highly favorable, elevating above mid 80's and cooling back down into comfortable porch-sitting levels. Rainfall would almost have been perfectly optimal, had it all fallen out of one cloud across the entire area. Yet, some got a little too much, some got some when it was almost late, but a large chunk of irrigated acres haven't had to move pivots very often across their PhytoGen varieties.
But it's cotton early in the year, so I have to gripe about something, and that has been cloud cover. With soil moisture and temperatures in adequate range, inconsistencies in amounts of unfiltered solar radiation between sunny and cloudy days is really playing tricks on much of our cotton crop, across the various growth stages.
Earliest PhytoGen planted acres may not appear to be in as great of shape as some of our later planted from roadside, but putting on a show under the skirt. Albeit the multiple stresses throughout April and May, heavy rainfall events, cooler than 50F nights, thrips pressure, herbicide dings, and testy soils, early vigor has weathered the storms and began initiating good fruit potential. The frequent change from sunny to overcast has played a test on reproductive stage plants still trying to understand where to devote resources. With many of the current PhytoGen varieties expressing higher levels of determinancy, fruit retention has remained greater than acceptable and vegetative growth has not yet become overly excessive.
Most of our May planted acres have had a favorable start, primarily in the pre-bloom stage. With more limited stresses throughout the month, many fields grew off as cotton wants to, being a perennial, tropical tree. Varying varieties and maturities iniated sympodial (fruiting) branches a node or two higher than the norm if not checked with a pre-square plant growth regulator application. PhytoGen brand PHY 545 W3FE typically sets its first fruiting branch lower than most true full-season maturing varieties, but still around position 7 this year in much of the May planted cotton. While fruit retention remains high, fruit set has been delayed with lower vegetative branching competing for light. PHY 443 W3FE, which acts as a mid to mid-full given area within the territory, has really demonstrated its early season vigor in 2021. But in many cases it has simply acted as a show off. In a few May planted Innovation Trials, PHY 443 W3FE, has pitched many of its first developed squares in an effort to continue to grow vegetatively. Great for side by side photos, not for early season shaping. Acres planted to PHY 360 W3FE and PHY 400 W3FE have initiated and retained squares, but have bounced between vegetative and reproductive growth with inconsistent sunlight.
Some of our overall best germination occured with June planted cotton in 2021. With many of these acres being dryland or following grain, warm soils, adequate moisture or timely rain events shortly after dusting in really aided in later planted cotton jumping out of the ground. However, many of these acres have seen little stress thus far, and are rapidly generating vegetative growth. Slightly more noticeable impact on foliage from herbicide applications to later planted, thinner cuticle cotton. With continued projected clouds and rain in the upcoming forecast, we will really want to monitor our late planted acres to ensure earliness.
One thing we have been blessed with in 2021 across most of our Central and East Georgia PhytoGen acres was uniform emergence and early vigorous growth. As we get into the period of the year where plant growth regulator timing is often much more crucial than rate, a uniform field aids in ease of management and decision making. To this point, the majority of our PhytoGen varieties needed little foliar application for the control of thrips, relying on seedling vigor, seed treatment, and/or in-furrow insecticides. While finding numbers of thrips still lingering, we have reached the stage in which they cause little economic impact.
Admittedly, I have not been to many locations in consistent enough rotation to make claim to any type of population dynamics, but I have seen very few tarnished plant bugs, with some below to near threshold levels in pockets. I am hearing discussion of tarnished plant bug damage resulting in low percentages of fruit retention in competitive cottons. I have witnessed aphid levels beginning to build on cotton plants in a few fields, with some terminal injury in low incidence.
If concerned with fruit loss from tarnished plant bug feeding and established aphid populations, talk to your location Corteva Crop Protection Territory Manager. Transform WG is a phenomonal choice for control of both tarnished plant bug and aphids, with minimal impact on many of our beneficial insects. At a 1.5 oz/ac use rate, I would typically like to save this application for bloom stage cotton, but in areas of usually low tarnished plant bug populations, there's not a better choice for peace of mind to eliminate insect pests that could be causing premature fruit shed. It minimizes impact on beneficials in hopes of not causing flare ups following application.
With tropical storm season approaching and continued mild temperatures, rain, and clouds forecasted, what should we focus on to promote rapid fruit development, minimize fruit abcission, and continue to promote on-time earliness of our cotton crop? The overly simple answer is growth regulation.
Regardless of growth stage, with current weather patterns, our plants our experiencing rapid cell expansion. Albeit experiencing excellent temperatures for cotton growth and development, flower initation has been hampered by inconsistent daylengths caused by changes in sun to cloud cover. Much of our generated carbohydrates are being directed to vegetative growth without something to slow cell expansion and rapid formation of gibberellic acid. In areas with more conistent cloud cover, "elephant ear" leaves can be found readily on varieties just reaching square initaiton. On true determinate varieties, these large sources may be of a benefit in the event we turn off dry at maturity during large demand for potatssium, but for varieties that express any indeterminancy, this may be sign of inefficient use of resources, and further shading light interception to subtending leaves directly feeding fruit. Similar for newest established crop, with minimal sunlight, our young plants are trying to grow rapidly to prepare for the dry, hot summer they believe is coming. On our earliest planted acres, where fruit retention remains high, we are holding vegetative growth relatively in check, but are in a more crucial stage of light interception.
If we are anywhere between 5-leaf cotton to bloom stages, we should be considering plant growth regulator applications to balance for reduced light interception and promote earliness at this point in the cropping season. While rate certainly matters based on environmental factors and variety, timing of our application is much more crucial. In most cases, a light dose earlier can be more effective than a heavier dose later. On our full season cottons, two sequential applications of lighter rates are often times much more beneficial than one heavy shot. Even in event our crop does not appear to be actively advancing stages, a light shot of mepiqut during low lights conditions will help to either find or more properly utilize available nutrients, what we have thrown in supplementing for optimum yield. Boll load is always our best pix, if we can increase the number of sinks, we can more efficiently use our sources.
As many of us are currently in the heat or kicking off side-dress applications, timing of mepiquat and micronutrients can become even more critical to insuring efficient use of our investment. Timing a plant growth regulator application in similar timing with our side-dress can help to drive to flower and seed development. In soils that are drier or at lower pH, supplementing either our plant growth regulator or side-dress application with boron may help promote flowering and efficient use of nitrogen. Tank-mixing zinc with our mepiquat could slow giberrellic acid formation and cell expansion, but assist in the mobility of macronutrients: nitrogen, phosphorus, and potassium.
It has been somewhat of a roller coaster, but we seemed to have found the stretch in '21 most similar to periods in '20. Much of our cotton is happy and growing like a weed, but without optimum light interception, photosynthesis, and proper photorespiration, we need to balance plant growth with some type of stress. Plant growth regulator is our best friend at this current stage in the game, and we are in excellent condition to visualize the importance of application timing over general rate as much of our crop sits today.
For general plant growth application timing recommendations for respective PhytoGen varieties across Central and East Georgia, you can refer to the "stoplight" chart above. If needing a more detailed prescription or just confirmation of your current plan, please contact myself or your local Corteva Seeds Sales Agronomist.
For more information about cotton production practices in your area, contact your state Extension cotton specialist. As always, your PhytoGen cotton development specialist also is available to discuss agronomic options.
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