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Meet What Eats Your Profit: Insect Management Strategies  

December 11, 2020 |

By Allison Mullen

As professor and Extension specialist at North Carolina State University, Hannah Burrack has spent years studying the management of tobacco’s insect pests and pollinators. In a recent presentation to North Carolina tobacco growers, she shared a collection of findings from experiments and observations in the field.

While Burrack recommends certain treatments to aid growers in their struggles with certain pests, the main takeaway from her observations in the experiment is clear: “Growers should be mindful of not making applications they do not need,” Burrack says. “This will help them save on costs as well as avoid issues of residue.”

We caught up with Dr. Burrack for insights into four common tobacco issues. Read on for her latest advice on how best to recognize and combat some of your field’s top challenges.

 

Tobacco Flea Beetles

For years, growers have been plagued by tobacco flea beetles, insects that prefer to feast on tobacco leaves early in the growing season and again close to harvest. To determine the best methods of treatment for these pests that can cause wide-scale damage, Burrack studied the effect of foliar applications.

These applications included Exeril (labeled in tobacco and contains the same active ingredient as Verimark), Admire Pro and a few other experimental pesticides not labeled for tobacco as of yet. For a pure study, she avoided the use of Admire Pro in the greenhouse so results would only contain the pesticides employed post-transplant.

Burrack divided the plants up and compared how the flea beetle populations were reduced with each separate chemical. Her findings revealed that, after each treatment, the flea beetle populations were greatly reduced.

Burrack warns of a caveat: “The effects of the foliar treatments are quite different depending on the time of the season and the size of the leaves,” she says. With small, younger plants, a foliar treatment on the leaves is much more effective than the same treatment on large leaves. “For this reason, if you are dealing with tobacco flea beetles later in the season, I would recommend using drop nozzles that provide good coverage on the lower part of the plant. This method will target the mature leaves the beetles are focused upon.”

Another thing to watch out for is the timing of the application when considering harvest. “Make sure the pre-harvest interval is acceptable to the legal growing standards,” Burrack advises. While Admire Pro can be an effective foliar treatment, for example, growers may hesitate to use this product late in the season as it has a 14-day pre-harvest interval.

While this experiment will lead to a better understanding of treatments for tobacco flea beetles later in the season, Burrack stresses that late-season tobacco flea beetle infestation is not a universal concern but a rarer condition. “Treating for these pests with a tray application in the greenhouse is standard practice; however, if you have not been experiencing an occurrence late in the season, do not pretreat with a foliar application as it is most likely not necessary.”

 

Thrips

Burrack’s next area of focus was the effect of foliar applications of pesticides to treat thrips infestation, though typically a foliar treatment is not the way growers have handled these pests in the past. “While you can generally eliminate the need for a foliar application with an effective greenhouse application of Actigard, in certain instances of extreme infestation another management strategy may be necessary,” Burrack says.

Burrack’s testing of foliar applications to control thrips later in the season did not show a significant reduction of infestation with the pesticides she used, some of which were experimental and not yet labeled for tobacco. However, Burrack advises that Actigard has shown promise acting as a foliar treatment.

When it comes to a foliar application of Actigard, timing is essential. In high-risk areas threatened with heightened thrip activity, the tobacco thrips flight and tomato spotted wilt virus (TSWV) intensity predictor tool can assist growers with application timing. This tool, found at www.climate.ncsu.edu/thrips, can help growers determine if and when to treat for thrips and TSWV. It also shows any past thrip and TSWV activity in an area.

It is important to remember that a foliar treatment only makes sense if you are experiencing a greater than 10 percent infestation rate. “Growers who have a less than 10 percent infestation rate should not use Actigard as a foliar application option as this method of treatment has been associated with plant stunting,” Burrack says.

In addition, the timing of the application must be perfect to account for the thrips’ flight schedule. “Because the timing of the foliar application is so critical, I’m less inclined to do foliar sprays, especially considering the unpredictability of weather patterns and a grower’s busy schedule, except in certain areas where the problem is extreme,” Burrack explains.

 

Tobacco Budworm

In Burrack’s observations in foliar treatments for tobacco budworm, she observed that the pests were not only seen earlier than usual but took a while to build up their population, resulting in a more prolonged infestation than normal. She treated with a foliar spray when the 10 percent threshold was reached and recommends growers do so as well.

The success of her application was evident in the reduction of the budworm population. However, Burrack warns that under a high-pressure situation, budworms could exceed thresholds twice and need more than one application. “Tobacco budworms are drawn to new leaves and buds not impacted by a foliar spray,” Burrack says. “The 10 percent threshold is an important rule to follow as if you go to a foliar treatment too early, it may not be as effective.”

 

TSWV Impact

With a mild winter, experts had predicted a higher than usual TSWV infection rate this season. However, growers actually saw less TSWV than in years past. Burrack credits this decline to rainy spring weather.

“The excessive rain after the transplants were in worked to suppress TSWV,” says Burrack. “Thrip larvae with new wings were susceptible and could not fly during this rainy period, helping contain the spread.”

 

 

 

Category: Diseases & Pests

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