Alabama Cotton Shorts
November 4, 2019
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November 4, 2019
Situation. The latter part of October ushered in rains which ended an extended period of great harvest weather. Since then, showers and overcast days have interrupted picking regularly, making it difficult to harvest for more than a couple of days at a time. Hopefully, we’re at least 65 to 70 percent harvested. The USDA October yield estimate for Alabama bumped up slightly compared to the previous months, from 942 to 851 lb/A. Even my colleague Dr. Ron Smith has upped his prediction from 850 to over 900 lb/A, so maybe we’ll get close to a million bales in 2019. I’ve seen some great, good, and bad and am still not quite so bullish. (Brown)
Below is the November 1 Alabama report from the USDA Macon Classing Office.
USDA Macon Classing Office. November 1. Alabama data. 186,523 bales |
Color grade 31 or better |
83 percent |
Average micronaire |
4.44 |
Average leaf |
2.89 |
Average strength, g/tex |
29.3 |
Average staple |
35.9 |
Average Uniformity |
80.8 |
Extraneous matter: bark – 1.9 percent grass – 0.4 percent |
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Cotton Leaf Roll Dwarf Disease (CLRDD) Update. The formal name for the virus which causes this disease is cotton leaf roll dwarf virus-AL or CLRDV-AL. The link below features a presentation given by Dr. Kathy Lawrence and posted in the Cotton Incorporated Webinar files in which she chronicles the initial findings and confirmation of CLRDV-AL.
http://www.plantmanagementnetwork.org/edcenter/seminars/Cotton/CottonBlueDiseaseAlabama/presentation_html5.html
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Ratooned cotton along with surviving stalks are reservoirs for plant parasitic nematodes as well as the cotton leaf roll dwarf virus (CLRDV-AL). Stalk survival increases the risk of damaging disease and nematode outbreaks next year in that or surrounding fields. This issue is particularly acute in extreme South Alabama where fields are not exposed to a killing freezes. To avoid continued nematode reproduction as well as to eliminate a CLRDV-AL source, stalks should be completely pulled from the ground as quickly as feasible this fall either with a stalk puller, disk harrow, or similar aggressive tillage, or possibly eliminated with herbicides. Planting a winter small grain or brassica cover crop following stalk pulling or fall tillage may also help suppress winter weeds such as henbit and white clover, which serve as hosts for CLRDV-AL. (Hagan)
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Plant Bug Management. Plant bugs can occur as an economic pest of cotton throughout the state of Alabama. Historically, they cause greater damage in the Tennessee Valley area of northern Alabama than elsewhere in the state. Adult tarnished plant bugs (TPB) move into pre-bloom cotton based on spring rainfall patterns. In dry periods, such as occurred in late-May and June 2019, wild host plants dry down rapidly, resulting in movement of high numbers of plant bugs into cotton over a short period of time. During wet springs, the opposite occurs -- a long, extended period of host plant decline leads to a long, drawn out migration of plant bugs into cotton.
Adult TPB feed on pinhead squares, resulting in abortion of these young fruiting structures. They also deposit eggs into the tender stems, and these eggs later hatch into small nymphs (immatures) in 10 to 15 days. These immatures typically hatch about the time cotton begins to bloom.
Scouting methods and treatment thresholds are well established for TPB. In pre-bloom cotton, all the plant bugs are migrating adults moving from wild host plants. A sweep net is the only effective survey method of counting TPB prior to bloom. One of two thresholds may be utilized during this period. The most common threshold in pre-bloom cotton is to use percent square retention. Eighty percent retention (which reflects 20 percent square loss) is the threshold to trigger intervention with insecticides. A second approach involves a sweep net, and the associated threshold is 8 adult TPB per100 sweeps. After first bloom, a drop cloth is the normal survey method. At this time, the majority of the population are immatures which have hatched from eggs deposited by migrating adults. When using a drop cloth, plants are briskly beaten over a cloth (3 x 2.5 feet) spread on the ground between two rows. The immatures, which do not fly, are then counted and tallied as the number per 5 feet. The treatment threshold with this survey method is 3 to 5 plant bugs per 5 feet.
A small plot (8 rows X 30 feet) replicated plant bug control trial was initiated at the Prattville, AL, research farm on June 25 (post bloom) on DP 1646 B2XF cotton planted on April 25, 2019. Immature TPB were approximately 1 per row foot prior to treatment. Post treatment counts (Table # 1) were made at 2, 7, and 14 days after treatment. This trial consisted of seven recommended insecticides or combinations plus an untreated control. Two 5-foot samples were taken in each plot, therefore the data are presented as the number of plant bugs per 10 row feet. In this trial all treatments gave acceptable control. However, based on previous research and observations by experienced consultants, it is recognized that plant bugs vary in susceptibility to some insecticides from region to region within the state. (Smith)
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Dicamba pH Buffers and Volatility. During the summer of 2019, our weed science program evaluated several commercial pH buffers with Engenia herbicide. It was clear that increasing spray solution pH decreased Engenia volatility. Certain commercial pH buffers such as Novus K and Maximum N-Pact B decreased dicamba volatility significantly. Both products contain boron as the main mechanism to increase tank pH. However, use rates of these products are quite high (44 to 192 fl oz/A) and can sometimes cause spray solution instability and tank precipitates, clogging tanks and spray lines. More research will be conducted in 2020 to better understand the efficacy of commercial pH buffers and explore options at lower use rates.
A large-field dicamba vapor study was conducted at Deatsville, AL, in June 2019. The results indicated that following the application of Roundup Powermax 32 oz + Xtendimax with Vaporgrip 22 oz + Intact (DRA), the total amount of dicamba volatilized from the 5-acre treated block was less than 0.2 percent of the total dicamba applied. This is well within the range of a current nationwide study (10-plus states) in which losses averaged 0.1 to 0.5 percent. Soybean bioassay plants in pots placed 15 feet away from the sprayed block and maintained for 2 days after application showed no more than 15 percent visual injury. More results will be available at our 2020 crop meetings and auxin herbicide trainings. (Li)
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New Extension Plant Pathologist. Dr. Amanda Strayer-Scherer recently joined the faculty of Auburn as an Extension Plant Pathologist with responsibilities in cotton, peanuts, small grains, ornamentals, and turf. Growing up in Florida, she received her undergraduate and graduate training at the University of Florida and served a post-doc at N.C. State. She’s had opportunities to conduct basic and applied research and participate in numerous Extension and outreach activities. Her email address is ascherer@auburn.edu, and you can follow her on Twitter @StrayerScherer. Welcome, Amanda.
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