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Oklahoma Cotton: Stand Problems; Cotton Fleahopper is Next Pest Up

Ernst Undesser
By Randy Boman and Jerry Goodson, Oklahoma State University June 19, 2017

Oklahoma Cotton: Stand Problems; Cotton Fleahopper is Next Pest Up

Texas A&M AgriLife Extension Service photo by Dr. Tom Isakeit

Current Situation

The Oklahoma cotton crop situation at this time is a very mixed bag. A lot of irrigated cotton was planted during the second week of May. As of this writing, cotton producers are still busy finishing up planting mostly dryland fields, working on weed management and watching for square formation.

 

 

Some of our irrigated acres had to be replanted due to high intensity rainfall/thunderstorm events in the second half of May and on into early June.

Many producers also have noted that small seeded varieties have many times exhibited poor seedling vigor and experienced significant difficulty with respect to stand establishment. A quick glance at some of the seed counts indicated that very small seed were noted (up to 6,400 seed/lb) for some varieties.

Some of these varieties have performed very well in variety trials and in producer fields last year, but this year challenging environmental/planting conditions impacted the germination and early season vigor of some of these small seeded types.

Many early planted irrigated acres had to be replanted. Some dryland producers whose fields have not received much rainfall have been boxed in by poor emergence of these varieties. Some growers have indicated they needed to replant but unfortunately don’t have the moisture to do so.

Therefore, some may be stuck with less than desirable stands in 2017. However, there still are a lot of earlier planted fields that are nearing the squaring stage at this time and should be on track for blooms in early July.

The Mesonet 30-Day Rainfall Accumulation graphic below illustrates the poor rainfall that has been obtained in the far southwestern corner of the state.

This low rainfall situation has impacted cotton acreage southwestern Jackson County, and several counties bordering or near the 100th meridian with Texas, including Harmon, Greer, Beckham and Roger Mills. Other, more eastern areas are in much better shape.

Planted acreage will be very large for the state, and we may possibly have the most cotton acres since the early 1980s – at perhaps 500,000 or so.

We have producers who are new to cotton and some who have planted cotton for the first time in many years.  Boll weevil eradication across most of the U.S. Cotton Belt, and in the state has been very successful and is a major contributing factor to the continued profitability of cotton production.

It has been a long, difficult, and challenging task to rid our state and most of the Cotton Belt of this invasive species that for such a long time negatively impacted our production.  We all need to do our part in keeping this pest from resurfacing in our state.  Some new cotton producers may be unaware of this ongoing program.

It is important for producers who are not familiar with this program to contact the Oklahoma Boll Weevil Organization to make sure their new fields are properly identified and trapped.  For more on this see the section below.

Weed Control

Many producers are making over-the-top applications of various herbicides.  High wind has been a challenge for many.  Producers should seriously consider any potential offtarget movement of their herbicides. This is important, especially when considering the new auxin herbicides recently labeled.

The new labels have extensive requirements to remain legal.  For an extensive review of this and information on herbicide selection, readers are encouraged to see the information provided in the May 11 edition of the newsletter.

Early Season Pests – Thrips and Fleahoppers

This year the crop is has wide ranging development – from squaring to just emerging. Early planted fields generally have received a thrips control sprays where later fields thrips have not been detected.

Herbicide Resistance Info


Fields just emerging with adequate moisture should outgrow thrips and control sprays should not be needed. WEEKLY scouting needs to be established as soon the plants emerge. Conversations with chemical distributors and consultants have indicated that unusual pests have occurred ranging from pill bugs to aphids.

Control measures were initiated in some situations.  Thanks to consultants Jerry Stoll and Andy Harrison for notifying this office.  As the crop reaches the squaring stage, the next major pest to be concerned about is the cotton fleahopper.

Since the introduction of Bt cotton and boll weevil eradication the cotton fleahopper has become the number one pest in Oklahoma. The cotton fleahopper usually feeds on young succulent weeds such as croton, goatweed, and horsenettle in early spring.

These weeds also provide an overwintering site for eggs. As the weeds mature, adults migrate to cotton which is beginning to develop pinhead squares. Fleahoppers insert their sucking mouthparts into the small squares.  These damaged squares later turn brown and are shed from the plant.

In addition to squares, the cotton fleahopper will also feed on other parts of the plant. If heavy infestations exist, new growth will be abnormal and whip-like in appearance. All stages of the life cycle will feed on the plant as long as it remains succulent.

As cotton matures, these insects migrate to weeds or other host crops. In southwest Oklahoma, the highest population typically occurs in cotton in early August, although this is not generally a problem that late in the season.

The life cycle begins with the female placing her eggs into the plant tissue by means of an ovipositor. The eggs hatch in approximately 1 week, and small nymphs (which are similar to the adults, except for being wingless) undergo five molts before reaching the adult stage. Egg to adult takes approximately 3 weeks with six to eight generations per year.

The cotton fleahopper adults are approximately one-eighth inch long, winged, and pale green in color. They are covered with small black spots and have four characteristic black spots near the wing tip. The nymphs are about one-twenty-fifth of an inch long, wingless, and pale green in color.

Numerous chemicals are registered for control of fleahoppers. In an ideal situation, fleahoppers should be controlled only when thresholds are exceeded in order to preserve beneficial insects since these will help control later occurring pests.

Unless the cotton is extremely late, after July 25, control of cotton fleahoppers generally is not economical.
Spray decisions should be based on the squaring rate and level of cotton fleahopper infestation. Usually when cotton fleahoppers (adults and nymphs) reach or exceed 30 per 100 terminals and squaring rates begin to decline, treatment is justified.

However, if cotton fleahopper numbers build slowly, fields can tolerate higher numbers before a reduction in squaring rate will occur. In most cases, fields will no longer be vulnerable to cotton fleahoppers once they begin to bloom.
Chemical control of cotton fleahoppers is a fairly easy to accomplish and several products provide good control.

However certain chemicals may not be advantageous. Care must be taken to preserve beneficial arthropods that will help in controlling cotton aphids and spider mites. Flaring of these pests can be avoided by using products that are “softer” on beneficials.

The list of chemicals that control cotton fleahoppers includes Orthene (acephate), Bidrin, Intruder, Centric, Carbine, Lorsban, Steward, Lannate, Dimethoate, and various pyrethroids. Vydate has historically been a product of choice. However, due to manufacturing issues, it is not available at this time.

Bidrin has a label allowing its use in cotton from emergence to prebloom, but you can’t apply more than 3.2 oz/ac during this period. According to research conducted by Texas A&M AgriLife Extension at Lubbock, products least likely to flare secondary pests include Carbine, Bidrin, Steward and low rates of Orthene (acephate).

Other insecticides such as Intruder and Centric won’t flare aphids and are probably fine to use as well, but these have been implicated in flaring mites. Pyrethroids are typically not recommended for fleahopper control because they tend to be very disruptive to beneficials and many times flare aphids. Pyrethroids can also exacerbate bollworm challenges in non‐Bt cotton.

Ernst Undesser
By Randy Boman and Jerry Goodson, Oklahoma State University June 19, 2017