The question in the headline has been asked in a lot of venues this winter and now the spring. But it may just be the wrong question. Perhaps we should be asking, instead, what will it take to make cotton profitable in 2015?
A paper written by four entomologists at Mississippi State University includes a figure that speaks volumes about why producers are shying away from the crop: The cost of foliar insect control in the Mississippi Delta has risen to an average of $140.49 per acre – three times what it was in 2005.
“When the other insect control costs are factored in, this is clearly not sustainable, and a more holistic approach to tarnished plant bug management is needed that does not rely only on foliar insecticides,” the paper says. (The authors are Jeff Gore, Angus Catchot, Don Cook and Fred Musser.)
The paper singles out tarnished plant bug because it has become the most important insect pest of cotton in Mississippi and the surrounding states or regions of Arkansas, Louisiana, the Missouri Bootheel and west Tennessee.
Several factors have led to the rise of tarnished plant bugs in the insect rankings. Bt cotton, or cotton containing the Bacillus thuringiensis gene, has improved the control of lepidopterous insects such as tobacco budworms, bollworms and pink bollworms. Another is the altered crop mix in the Mid-South.
“When you look at all the issues that can influence a pest population, one of the biggest is we have a shrinking amount of acreage of cotton so that target on a cotton field becomes bigger and bigger,” says Gus Lorenz, Extension entomologist with the University of Arkansas.
“You still have the same numbers coming out of corn and soybeans and wild hosts and things like that, but you have less acreage for those plant bugs to go to when that cotton starts fruiting,” said Lorenz, speaking at the Southern Consultants Conference sponsored by Adama in Memphis, Tenn., just prior to the Mid-South Farm and Gin Show.
Lorenz showed a slide of the “edge effect” that tarnished plant bugs moving from drying corn or soybeans can have on cotton. The first set of cotton rows next to a soybean field has almost no bolls on the plants.
“You can see the impact of not controlling plant bugs in that untreated check,” he said, referring to a photo from test plots at the Lon Mann Cotton Research Station at Marianna, Ark. “That’s the kind of pressure that we’re dealing with so when I show these numbers we’re dealing with you’ll realize the pressure is pretty intense.”
Another factor is the number of insecticides that no longer provide reliable control of tarnished plant bugs. Resistance to the pyrethroids was widespread by 1999 and to organophosphate insecticides by 2005.
Foliar insect control costs last peaked at $86.50 an acre in 1992 prior to the introduction of Bt cotton and boll weevil eradication. Those costs dropped below $20 an acre during the height of the spraying of malathion for boll weevil eradication in 1999 and 2000. They’ve been rising steadily since 2005.
The authors of the paper, entomologists who work for the Mississippi Agricultural and Forestry Experiment Station or for Mississippi Extension, have put together a list of “Best management practices for tarnished plant bug in cotton.”
At the top of the list is field selection and planting arrangement. “Tarnished plant bug infestations within a cotton field are significantly influenced by other agronomic crops and wild hosts adjacent to that field,” said the entomologists.
“Edge effects can be minimized by blocking cotton fields together and separating them from corn and early planted soybean fields. Additionally, care should be taken to manage wild hosts before they flower and hold heavy infestations of tarnished plant bugs. The overall goal of field selection should be to minimize the number of edges where cotton is adjacent to other plant hosts.”
Variety and planting date can also be important. Growers should consider leaf pubescence and varietal maturing in the decisionmaking process on cotton varieties for 2015.
“The density of hairs on cotton leaves can have an impact on tarnished plant bug injury in cotton,” the entomologists said. “With similar numbers of plant bugs, a hairy leaf variety maintains significantly greater levels of square retention compared to a smooth leaf variety.”
“In our trials, the later the planting date, the more insecticide applications were required and the greater the yield loss from plant bug damage,” says Jeff Gore, a research entomologist at the Delta Research and Extension Center. “If we planted mid- to late-April and early May, we only had to make three or four applications during the entire season. With mid-May or early June planting, we had to make a lot more.
Lorenz and Angus Catchot have also said that applying the insect growth regular Diamond alone or in combination with other materials can also help growers reduce the amount of injury from tarnished plant bugs.
12 things you can do
The complete list of best management practices include:
Plant as early as possible (before May 7)
Plant an early maturing variety
Arrange plantings to avoid “edge effects”
Promote earliness (early season thrips, disease, and weed management)
Avoid smooth leaf varieties
Reduce nitrogen rates (Excess nitrogen leads to rank growth and delayed maturity)
Delay irrigation as long as possible (can cause rank growth and delayed maturity)
Use optimum application practices (nozzle type, ground vs. air, timeliness, etc.)
Make sequential sprays and shorten intervals to 4-5 days during heavy pressure
Rotate insecticide classes
Use Diamond during late squaring/early flowering (when adults are migrating)
Do not chase a few pounds of lint in the top of the plant with multiple sprays (more research is needed on when to stop spraying for plant bugs).
For more on this topic, see more at: http://www.mississippi-crops.com/2015/03/05/best-management-practices-for-tarnished-plant-bug/#sthash.i2hYkmqf.dpuf