FEATURES

Challenging Bollworm Year Expected In The Delta

BY JEFF GORE, ANUGUS CATCHOT, DON COOK AND WHITNEY CROW

The 2019 season was one of the most challenging years we have had from a bollworm standpoint in both cotton and soybeans. The issue was not from a numbers position where they overwhelmed the traits and foliar insecticides. It was more an issue of population dynamics and how the egg lays occurred.

Rather than a normal population growth curve where the number of eggs starts off low and increases over a seven-day period ending with a heavy egg lay, we had a low trickling of eggs that persisted over several weeks. This made decisions to spray very difficult.

2019 Sprays Delayed

In a more typical year, growers can make a spray when the egg numbers increase and peak, which usually occurs about the middle of July. The egg lay drops to almost zero for a period of time and then peaks again in about a month, triggering a second spray.

In 2019, we never really saw the first peak in eggs that makes the decision to spray easy. In cotton, we typically got reports of low egg levels that ended up turning into low levels of larvae and damage that got worse over time, especially north of Highway 82.

As a result, we had a lot of sprays go out a little later than optimum in two-gene cotton varieties. In most cases, even if the sprays went out late, the survival and damage levels we saw were mostly not economical. In other words, the sprays worked, just not as good as they could have or as good as we would have liked.

Extended Corn Planting Hurt

The population dynamics of bollworms in cotton and soybeans are mostly influenced by corn. We believe the extended planting window and

Follow thresholds when treating for bollworms.

later planting dates for corn were a primary cause for what we experienced in 2019.

Trying to predict what insect populations will be like during July and August is almost impossible in April. And this year is setting up a lot like last year from a bollworm standpoint. Getting corn planted in a timely manner has been difficult with the rains this spring and will likely influence bollworms in cotton and soybeans.

As of the third week in April, we expect another challenging year from a bollworm perspective. We will collect bollworms from crimson clover in a couple weeks, but that will not tell us a lot about the upcoming crop season. Because corn is such a good host during June, even low populations during the spring can turn into big populations during July.

Similarly, big populations in clover don’t really matter if green corn silks

are not available when bollworms that developed on clover emerge as adults. The point is that corn is the key.

Follow Thresholds

For 2020, the best advice we can give is be prepared for anything and follow our thresholds. In twogene cotton (Bollgard II, TwinLink, WideStrike), we are still suggesting an egg threshold of 20% of plants with at least one egg. In three-gene cotton (Bollgard 3, WideStrike 3 and TwinLink Plus), we are sticking with a damage threshold.

We will monitor what is happening in corn and at more southern locations to give updates throughout the summer.

Localized Research Keeps Cotton In Context

All U.S. Upland cotton producers pay an assessment to The Cotton Board. In turn, it contracts with Cotton Incorporated to conduct research and promotion to increase the demand for and profitability of cotton.

Many cotton producers are aware of the national and regional research projects conducted by Cotton Incorporated but may be unaware that 7.5% of cotton assessments are dedicated to state-specific research. These funds are divided among the cotton-producing states according to production levels. The State Support Program is designed to address the specific needs of individual states.

A grower-led committee within each state sets priorities, requests proposals from local research institutions and allocates its share of SSP funds. In my territory — the Southeast cotton-growing region — all six states have certified producer organizations that set up the SSP committee meetings.

Cotton growers from each state hear researchers from land-grant universities and Extension agencies talk about specific projects and emerging localized concerns.

The SSP committee makes decisions about which projects are the most important for its state and allocates funding accordingly. BY MONTY BAIN DADEVILLE, ALABAMA

Teamwork Gets Results

Kater Hake, vice president of agricultural research at Cotton Incorporated, says, “Each cotton state has different combinations of soils, weather, pests and rotations. As a result, growers want research focused on their conditions and their fields. The structure of the Cotton Research and Promotion Program guarantees this connection to local conditions. Roughly 160 growers on The Cotton Board and Cotton Incorporated from every cotton-producing state volunteer their time to guide the research program.”

Once projects have been identified by the state committee, they are managed by Cotton Incorporated’s Agricultural and Environmental Research Division’s staff. The division team comprises seven research directors, with different areas of expertise and specialties, who support a network of more than 300 public sector scientists. The division team evaluates the specific concerns of each state and then makes research recommendations. Cotton Incorporated is currently managing more than 400 research projects.

In some cases, several states may be trying to address the same issue. When that happens, the team will use core

budget, not SSP funds, to address the national or regional-level project. Across the Cotton Belt, there is concern surrounding herbicide-resistant weeds, producer profitability and sustainability. Cotton Incorporated has numerous research projects addressing these widespread issues.

Cotton Incorporated research staff and Drs. Ed Barnes and Don Jones agree yield and quality are priorities in the Southeast, reflected by strong grower support for on-farm variety trials. “Growers understand that yield increase is what is keeping them in business,” Barnes says. Jones adds, “Farmers in the Southeast are also concerned about the potential damage from cotton leaf roll dwarf virus.”

Southeast State Projects

Below are a few of the major issues being addressed in the Southeast through SSP-funding research.  Alabama – Profitable grower values for fiber and cottonseed products.  Florida – Yield, fiber value and disease concerns.  Georgia – Weed resistance management, cost of production and cottonseed value.  South Carolina – Soil health and nutrient recommendations, particularly potassium.  North Carolina – Planting seed quality, control of tarnished plant bug and Bt-resistant bollworms.  Virginia – Deer damage to cotton and bear damage to cotton modules.

I encourage Southeast cotton producers who are interested in serving on your state’s SSP committee, or who are just interested in knowing more about localized research, to contact me. I am happy to put you in touch with the researchers and certified producer organizations in your state. Because the SSP closely follows the mission of Cotton Incorporated, I know it is something we can all get behind.

Link Found Between Pigweed And Plant Bugs

BY AMANDA HUBER SOUTHEAST EDITOR

The reasons to aggressively battle glyphosate-resistant Palmer amaranth (pigweed) are well known. This pest will outcompete any crop, and if left uncontrolled, can take over entire fields. But even with 20 years of research into this formidable foe, new evidence suggests yet another reason: a link between Palmer pigweed and tarnished plant bugs.

Research led by University of Georgia graduate student Taylor Randell with UGA Extension weed specialist Stanley Culpepper and Extension entomologist Phillip Roberts showed pigweed attracts tarnished plant bugs into the field. The insects then feed on cotton plants.

In research conducted in 2017- 2018, plant bugs damaged 9% to 15% of cotton terminals in plots kept free of Palmer amaranth. However, when pigweed was allowed to remain in the plot for up to 35 days before removal, damaged cotton terminals ranged from 25% to 39%. Cotton terminal damage from plant bugs influenced by the presence of Palmer amaranth caused yield loss at the Macon County site in one of two years.

Check Fields For Both Pests

Roberts says tarnished plant bug is becoming a more frequent pest but is still considered an occasional pest.

“I have heard more chatter on this pest in the past few years than in the previous 15,” he says. “It is a very serious pest in other parts of the country. Absolutely check your fields for them. If you have plant bugs, they can be bad. But it’s rare that we’re going to spray for them. Maybe 5% to 10% of the acres will need to be treated to control this pest.”

The link between Palmer amaranth and tarnished plant bug adds more science behind UGA’s decade-long recommendations for managing Palmer amaranth. These include:

Blooms with dried, brown anthers, or “dirty blooms,” indicate tarnished plant bug or plant bug nymphs fed on larger squares the plant did not shed. RONALD SMITH, AUBURN UNIVERSITY, BUGWOOD.ORG

 No Palmer up at planting.  Two effective at-plant residual herbicides used at rates that will not hurt the cotton crop.  Timely post applications.  Improving late-season weed coverage and control, while reducing cotton injury by applying conventional chemistry through your layby rig or hooded sprayer.

What To Look For

As for the tarnished plant bug, according to the “North Carolina Cotton Insect Scouting Guide,” early season monitoring for activity is recommended. This is especially important for retention counts of small squares at approximately 1/8 to 3/16- inch long, including bracts. If square retention is greater than or equal to 80%, more comprehensive sampling for live tarnished plant bugs is probably unnecessary.

As recommended in the guide, “If retention rates of small, upper and other first- or second-position squares drop below this level, further sampling for live tarnished plant bugs may be needed. Usually, one terminal square (or its missing position) and one first or second position square (or its missing position) two or three nodes from the top of the plant are inspected per plant. These inspections are from 25 randomly selected plants in a field for 50 squares total. Sweep net sampling for tarnished plant bug adults and large nymphs typically involves taking two sweeps at six to 10 locations per cotton field.”

But Roberts says producers shouldn’t be too aggressive in treating plant bugs.

“Plant bugs are a problem when we start to square,” he says. “We have good thresholds, and if you have a problem, address it. If not, let Mother Nature and beneficial insects come into cotton and start establishing to help us with pests later in the season.”

As Roberts points out, squaring cotton is attractive to predatory insects like big-eyed bugs that help with other pests.

“Squaring is a critical window in that you don’t want to go in and upset the apple cart, so to speak. Tarnished plant bug is more of a pest in other parts of the country than in Georgia.”