Louisiana Cotton Bulletin. LSU AgCenter Cotton Research and Extension

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Louisiana Cotton Bulletin Volume 6, Issue 14 ARTICLES THIS ISSUE September 2,, 20092 Crop Report Dr.

1 Louisiana Cotton Bulletin Volume 6, Issue 14 ARTICLES THIS ISSUE September 2,, Crop Report Dr. Donald Boquet, Jack and Henrietta Jones Endowed Professor of Agronomy and Interim Cotton Specialist..p. 1 Insecticide Termination Guidelines Dr. Roger Leonard, Professor of Entomology and J. Hamilton Regents Chair in Cotton Production.....p. 2 List of LSU AgCenter Cotton Personnel......p. 6 Crop Report, September 2, 2009 Donald J. Boquet, PhD Airplanes have been very active applying defoliates this week as the dry weather has increased the rate of boll opening and many fields are greater than 60% open bolls. Fields now being Sep. 2, 2009 defoliated have good to excellent yield potential, many with 2+ bales per acre potential. The lower than normal temperatures we experienced last week and again this week will have no affect on mature and almost mature cotton. Defoliation chemicals will work well under these conditions. However, cotton that is still filling bolls will be affected and management of fields will also be affected. Usually, we can expect to harvest bolls set in mid-august and even in late August. At this time of year we usually accumulate DD60s at optimal or near optimal rates with night temperatures in the low 70s and daytime temperature in the low 90s. Rate of boll fill for late bolls is always slowed some by the shorter day lengths in September but is still rapid enough to complete maturation by late September. However, recent DD60 accumulation has been averaging only 12 to 15 per day; well below optimal for rapid boll development. Combined with the shorter days, if the cool weather persists, boll development rate will be slower than normal. This becomes a major factor in whether to continue to wait for the latest bolls to complete development, meanwhile incurring additional insecticide expenses, and possibly placing the majority of the crop at risk from weather events. This year, in particular, many fields have a bottom crop open and a gap in fruiting caused by the dry weather in June/July and other factors. The top crop would be a welcome addition to the bottom line and the decision on whether to continue protecting these developing bolls is never clear cut. It is made more difficult this year by the arrival of early cool fronts that may extend boll development. The article below on IPM termination timing should be helpful in making management decisions during the next two weeks. 1

2 Louisiana Cotton Bulletin When to terminate insecticide applications in cotton B. R. Leonard, PhD For most producers and consultants, the proper time to stop applying insecticides for late-season cotton insect pest management is an important consideration and requires a balance between the cost of applying a treatment and final yield loss. One key point to recognize is that profits through increased yields and improved fiber quality must exceed the cost of these control strategies to justify late-season insecticide treatments. However, it is just as important to be aware of the fact that during the latter stages of flowering, fruiting forms reach a peak value and plants lose the ability to fully compensate for their loss during the remainder of the season. The indeterminate growth pattern of cotton also allows bolls to develop on the plant over an interval of several weeks. In fields where insect pests have been successfully controlled for the entire season, the contribution of bolls in the top of the plant is usually minor compared to those bolls at lower fruiting positions on the plant. Numerous cotton insect pests injure cotton during the production season, and a single action threshold to terminate insect control strategies is not likely appropriate for all pests. Numerous studies during the previous decade have demonstrated that heat unit (HU) accumulation of bolls using anthesis (pink flower) as the starting point for boll maturation is a consistent method of gauging the susceptibility of bolls to pests. As shown in Figure 1, there is considerable variability in the ability among cotton pests to injure bolls. The decision of when to terminate late-season insect pest management has been a persistent problem for the cotton industry. Many of you are aware of the COTMAN program, which can provide information on plant development during the entire season. COTMAN data gives a reference and seasonal perspective of crop fruiting patterns that can be coupled with insect and mite infestation counts to make a well-informed decision. A sub-program routine, BOLLMAN has been used to estimate the critical time to terminate insect pest management strategies at the end of the growing season. This program uses cutout [main stem nodes above white flower (NAWF) 5], as the endpoint for the last effective boll population set on the plant. Many bolls produced by the plant after cutout does not have enough time remaining in the season to produce mature cotton fibers. As a general rule, after cutout has occurred and the crop has accumulated 350 to 550 HU, harvestable bolls are considered safe from attack by most fruit feeding insect pests. If one wants to hedge the measurement of boll tolerance with the definition of cutout using NAWF 4, then HU accumulation rules remain the same. Physiological cutout is a key factor that must be defined accurately for each situation to eliminate late-season treatments used to protect cotton bolls that normally abscise or will not produce mature fiber. Unfortunately, there are situations in which the crop develops in such a manner that the NAWF never progresses to within five main stem nodes of the plant terminal. Under these conditions, an alternative to using a physiological basis for cutout is to estimate the latest possible cutout date using a calendar day. This endpoint of crop development uses long-term weather data for a specific location and represents the last day in which a white flower has a 50% chance of receiving enough HU to mature into a boll of sufficient size and quality. For most of Louisiana, long-term weather averages suggest the last week of August should be considered as our calendar based cutout date. Therefore, if a producer is interested in maturing bolls set on the plant during that week, insect control strategies will need to be used until those bolls have accumulated at least 350 HU. During common September temperatures, that is about 2-3 weeks. This year, however, as noted in the above report, late August and early September temperatures have been lower than normal, which has reduced DD60 accumulation by about 5 per day and extended the number of days for bolls to be generally safe from damage from insects to about 25 days. 2

3 Louisiana Cotton Bulletin Determining cutout with either a physiological or calendar measurement requires some field observations and record-keeping. Many growers and consultants are busy during the production season and do not have access to this timely information. Therefore, I have listed several key items to consider in this process of terminating insecticide applications. Each field is a different environment under individual management and should be examined independently. The value of the last upper bolls (top 4 main stem nodes) is far less than those lower on the plant and any action threshold for initiating treatment should be increased when considering treatment. This is especially true when considering that late-season treatments are usually combinations of expensive insecticides. Terminating insecticide treatments early may result in some minor boll damage on the upper main stem nodes, but rarely will significant yield losses occur. To properly mature a full-season cotton crop, especially on fertile soils with maximum nutrient applications, some upper boll retention is usually necessary. Most cotton insect pests have difficulty in damaging large bolls and prefer squares. Even under significant infestations during the late season damage is usually not as severe as that observed earlier in the year. The exception is with stinkbugs and large fall armyworms. When the last bolls on the upper nodes that have reasonable expectation for harvest become hard when pressed between fingers or are speckled (normal change not due to herbicide injury) in color then yield losses caused by insect on those plants are unlikely. Special situations can occur with defoliating caterpillar (soybean loopers, beet armyworms) pests. Do not allow more than 40% defoliation until the plants have matured to the point that harvest aids can be applied. In many instances, the final applications to control late-season pests should not target the entire field, but isolated green areas because these areas are more attractive. If these areas constitute only a minor portion of the field, then field-wide losses will be minimal without any treatment. 3

Boll Abscission (%) 80 60 40 20 Boll Weevil 350 HU B. Armyworm 360 HU T. Plant Bug 327 HU F.

60 00 16 65 50 17 70 00 17 75 50 18 80 00 18 85 50 190 0 100 Figure 1.

4 Boll Abscission (%) Boll Weevil 350 HU B. Armyworm 360 HU T. Plant Bug 327 HU F. Armyworm > 850 HU Bollworm Stink Bugs 426 HU 560 HU 0 Heat Units Figure 1. The effects of boll maturity (heat unit accumulation after anthesis) on insect pest-induced boll abscission. Figure 2. This 30-day-old boll is safe from insect pests and does not need IPM protection. Figure 3. This 25 day old boll is generally safe from most insect pests, but could potentially be damaged by stink bugs or armyworm. 4

pests for 7 to 10 more days before it is safe from damage. Figure 6.

5 Figure 4. This 20-day-old boll is also generally safe from most insect damage. Figure 5. This 15-day-old boll will need monitoring and protection from insect pests for 7 to 10 more days before it is safe from damage. Figure 6. Example of a small 10-day-old top boll on September 2, which will contribute very little to yield, and should not be protected from insect pests. ********************************************************* 5

6 Below is a list of contacts, parish and area field agents and state extension specialists. They are prepared to assist you with any questions or problems you have. Avoyelles COTTON FIELD AGENTS PARISH AGENT PHONE Trent Clark Carlos A. Smith Jr tclark@agcenter.lsu.edu CSmith@agcenter.lsu.edu Bossier Joe Barrett JBarrett@agcenter.lsu.edu Caddo John Levasseur JLevasseur@agcenter.lsu.edu Caldwell Jim McCann JMcCann@agcenter.lsu.edu Catahoula Glen Daniels GDaniels@agcenter.lsu.edu Concordia Glenn Daniels GDaniels@agcenter.lsu.edu East Carroll Donna Lee drlee@agcenter.lsu.edu Evangeline Keith Fontenot KFontenot@agcenter.lsu.edu Franklin Carol Pinnell-Alison CPinnell-Alison@agcenter.lsu.edu Grant Matt Martin MMartin@agcenter.lsu.edu LaSalle Jim Summers JSummers@agcenter.lsu.edu Madison Ralph Frazier or 2483 rfrazier@agcenter.lsu.edu Morehouse Terry Erwin Richard Letlow or or 5741 terwin@agcenter.lsu.edu rletlow@agcenter.lsu.edu Natchitoches Donna Morgan dsmorgan@agcenter.lsu.edu Ouachita Richard Letlow or 5741 rletlow@agcenter.lsu.edu Pointe Coupee Miles Brashier MBrashier@agcenter.lsu.edu Rapides Matt Martin MMartin@agcenter.lsu.edu Red River Richland Keith Collins KCollins@agcenter.lsu.edu St. Landry Keith Normand KNormand@agcenter.lsu.edu Tensas Dennis Burns dburns@agcenter.lsu.edu West Carroll Myrl Sistrunk MSistrunk@agcenter.lsu.edu EXTENSION SPECIALISTS Cotton Specialist Donald Boquet (cell) Weed Specialists Bill Williams Daniel Stephenson Donnie Miller (cell) (cell) dboquet@agcenter.lsu.edu bwilliams@agcenter.lsu.edu dstephenson@agcenter.lsu.edu dmiller@agcenter.lsu.edu Entomology Specialist Roger Leonard rleonard@agcenter.lsu.edu (cell) Nematology Specialist Charlie Overstreet Coverstreet@agcenter.lsu.edu Pathology Specialist Boyd Padgett (cell) bpadgett@agcenter.lsu.edu Economics Specialist Gene Johnson GJohnson@agcenter.lsu.edu Soil Fertility Specialist J. Stevens JStevens@agcenter.lsu.edu (cell) Extension Associate Brandi Woolam (cell) BWoolam@agcenter.lsu.edu Louisiana State University Center Agricultural Center, William B. Richardson, Chancellor Louisiana Agricultural Experiment Station, David J. Boethel, Vice-Chancellor and Director Louisiana Cooperative Extension Service, Paul D. Coreil, Vice Chancellor and Director Issued in furtherance of the Cooperative Extension work, Acts of Congress of May 8 and June 30, 1914, in cooperation with the United States Department of Agriculture. The Louisiana Cooperative Extension Service provides equal opportunities in programs and employment. 6

September 2006 Volume 1, No. 1

September 2006 Volume 1, No. 1 In This Issue: Sweet Potato Crop Update Sweet Potato Weevil Trapping Program Update Late Season Insect Concerns Proper Curing of Freshly Harvested Potatoes Market Outlook