Texas Cotton: Plant Growth Regulator Considerations
Recent storms have provided much needed moisture across much of the High Plains and parts of the Panhandle. Unfortunately, these storms also brought hail and high winds that have caused varying levels of damage to already delayed cotton crops. Some fields were completely destroyed in the areas where large amounts of hail and/or high winds were observed. Currently, there is no hard number to report in terms of lost cotton crops.
Reports from Texas A&M AgriLife County Extension Ag Agents and IPM Agents indicate that some fields have already been replanted to cotton or sorghum. Rainfall amounts reported by the Texas Tech University West Texas Mesonet System (Current and Past Precipitation) vary greatly thus far for the month of June and range from a high of 5.13” to a low of 0.93” for Anton and Friona, respectively. These amounts have provided enough moisture to germinate cotton planted to dryland production fields in some areas but more is needed at timely intervals to maintain established stands.
Based on data from the CottonHeatUnits.com website, heat unit accumulations at Lubbock total 699 DD60s, which is 95 above our long term average of 604. In general, the cotton stands that have been established and managed to dodge the weather bullet appear to be in fair to good condition. Growth stages of these crops range from just emerged or emerging to very early squaring.
During my travels to the eastern part of the region earlier last week I determined that two dryland variety trial locations we planted had received some moisture following dry planting and were beginning to emerge. With high temperatures forecast in the 90s for the next ten days and only slight chances for additional rainfall, cotton crops that have begun squaring should be watched closely for moisture stress, especially in areas where little rainfall was experienced during the recent storm events.
Plant Growth Regulators
Questions concerning mepiquat-based (Pix, Pix Plus, Mepex, Mepichlor, Mepiquat Chloride, Mepex GinOut, Stance, and others) plant growth regulators (PGRs) are being asked. Mepiquat chloride (MC) reduces production of gibberellic acid in plant cells that in turn reduces cell expansion, ultimately resulting in shorter internode length. MC will not help the plants compensate for earlier weather or disease damage by increasing growth rate.
It may, under good growing conditions, increase fruit retention, control growth and promote earliness. MC should not be applied if crop is under any stresses including moisture; heat; severe spider mite, insect, or nematode damage; disease stress; herbicide injury; or fertility stress.
Results from our replicated testing indicates that we observed from 5 to 20% reduction in plant height (compared to the control) from 16 oz of 4.2% a.i. MC material applied in up to 4 sequential 4-oz/acre applications starting at match head square (MHS) and ending at early bloom. We have been able to “shave” about 1 node from the growth of the main stem at some locations, which can result in about 3-5 days earlier cutout. Low rate multiple applications beginning at MHS have generally provided more growth control than higher rate applications made at first bloom or later.
Mepiquat chloride (MC) based products have been around for many years. Several plant growth regulators (PGRs) based on the same active ingredient are now available. Pentia is a formulation of mepiquat pentaborate – a different molecular structure than MC. Mepex Gin Out contains the same amount of MC active ingredient as others, but contains an additional PGR. Refer to the product labels or contact local representatives to ensure you understand the correct use of these products.
Mepex, Mepichlor, Mepiquat Chloride and other generics 4.2% active ingredient (a.i.)/gallon or 0.35 lb/gallon a.i.
Mepiquat pentaborate molecule (different from MC) 9.6% a.i./gallon or 0.82 lb/gallon a.i.
Mepex Gin Out
4.2% a.i./gallon or 0.35 lb/gallon a.i. with 0.0025% Kinetin (a cytokinin). Cytokinins are plant hormones that promote cell division and growth and delay the senescence of leaves. This product has use guidelines similar to other MC materials.
Stance Bayer CropScience’s Stance product is a mepiquat chloride based PGR. It is a 4 to 1 ratio of mepiquat chloride and cyclanilide (0.736 lbs/gallon mepiquat chloride plus 0.184 lbs/gallon cyclanilide). Cyclanilide is an auxin synthesis and transport inhibitor. Auxins are generally referred to as compounds which have the capacity to induce cell elongation. The inhibition of auxins could reduce cell elongation and inhibit growth.
Producers should be aware that the mepiquat chloride concentration in Stance is about twice as high as most of the other materials we have become accustomed to applying. THEREFORE THERE IS A CORRESPONDING REDUCED RATE. If you have specific questions concerning this product, visit with your local Bayer CropScience representative.
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