banner ad

Reduced Carryover, Reduced Pests

December 11, 2020 |

By Julia Ellis

After bringing a tobacco harvest safely through a gauntlet of aphids, hornworms, budworms and grasshoppers, growers must protect their tobacco from insect pests that don’t like it green: cigarette beetles and tobacco moths. These ravenous ravagers plague stores of cured tobacco, eating holes into the profits of growers, manufacturers and distributors.

Beetle Mania

The cigarette beetle Lasioderma serricorne has been bugging humans for thousands of years. In fact, a specimen of this small (2 mm to 3 mm) reddish-brown beetle was found in King Tutankhamun’s tomb.

One of two stored product pests in the Anobiid family, larvae of the cigarette beetle are fond of munching more than just stored tobacco. These white, hairy worms also eat flour, dried fruit, rice and nuts. The adults pass on a symbiotic yeast to their offspring, which enables them to munch on less nutritious food, such as bookbinding paste.

The life cycle of the cigarette beetle can be accelerated by warm temperatures and plentiful food. Females lay 10 eggs to 100 eggs in a food source, such as tobacco. After about a week, the larvae emerge. They eat and molt four to six times over a period of five to 10 weeks before creating a cocoon for pupation. One to three weeks later, adults emerge and reproduce, living up to four weeks. Generations can overlap during warmer temperatures.

Cigarette beetles both damage and contaminate tobacco. When feeding, they create small holes similar to those created by flea beetles in green tobacco. Their bodies, body parts, larvae, cocoons and excrement can contaminate a bundle of tobacco. They leave behind a powdery waste, which gives tobacco an unpleasant flavor.

Moth Menace

Ephestia elutella, or the tobacco moth, is also commonly known as the warehouse moth or chocolate moth. Adults have gray wings with black markings and a wingspan of 14 mm to 20 mm. Like the cigarette beetle, the larvae of this moth feed on dry plant produce, including tobacco, cocoa beans, cereals and more.

After emerging from the cocoon, adults can mate within a few days. Females then lay 150 eggs to 200 eggs on a food source. After a week, the eggs hatch. The larvae worm into the food source and hide, eating and molting for several months. After the fifth instar, or molt, they leave the food source and find a place to go into diapause for the winter. When summer comes around, they go through their final instar, creating a pupa. A month or so later, adults emerge.

Tobacco moth larvae leave larger holes in stored leaves than the cigarette beetle and can strip tobacco leaves down to their veins.

Damage from both insects can greatly reduce the quality and grade of tobacco.

Clean and Spray

Being strategic about storage is the first line of defense against these pests. Experts at North Carolina State University recommend keeping tobacco in the curing barn so it can be reheated if pests invade. If other storage facilities are required, these should be thoroughly emptied of organic material. All plant refuse should be burned away from the site.

Stored tobacco should be checked regularly for signs of insect pests. Pheromone traps can be used to check for the presence of cigarette beetles. Sticky hanging traps can be used to catch resident moths.

Products containing the bacterium Bacillus thuringiensis can be used to prevent and treat tobacco moth infestations. Growers should spray the storage facility with a mixture of 0.5 oz of Biobit HP or DiPel DF per 2.5 gallons of water, applying 0.5 gallons per 1,000 square feet. Tobacco leaves can be sprayed as they are bundled with 0.2 oz of Biobit HP/DiPel DF per quart of water applied to 100 pounds of tobacco in a fine mist spray. If an infestation is identified after several weeks in storage, the bales should be unwrapped and the loose leaves should be sprayed before rebundling. For tobacco hung on sticks, both sides of the leaves should be sprayed.

Gassed Resort

Cigarette beetle infestations require fumigation, which must be performed by a professional. Phosphine (PH3) gas has been commonly used since the late 1950s for control of the cigarette beetle. Successful fumigation with phosphine is dependent on maintaining phosphine concentration through all of the tobacco.

Exposure time and the temperature of the tobacco bale center are also critical. The tobacco must be 61 degrees Fahrenheit or warmer for successful fumigation. Depending on phosphine concentration and tobacco temperature, tobacco may need to be fumigated for six to 12 days.

The long-term use of phosphine has resulted in cigarette beetles that have developed resistance to the gas. Companies such as Fumigation Service and Supply Inc. and Degesch America Inc. offer kits to test for phosphine resistance. If insects do not show resistance, they are called “susceptible” and can be treated at lower concentrations of phosphine for less time. Phosphine-resistant beetles may be treated with higher concentrations of the gas or with alternative fumigants.

The tobacco moth can also be controlled by fumigation. Because it is more susceptible to phosphine than the cigarette beetle, standards for cigarette beetle fumigation are used.

Industry researchers are investigating freezing and controlled atmosphere—adjusting ratios of carbon dioxide, oxygen and dinitrogen—as alternatives to fumigation. Deep freezing would provide control in climates below the 61 degree temperature needed for fumigation. These methods would have less of an environmental impact and would not affect product flavor.

Carry On

Although cigarette beetles and tobacco moths are still creating headaches for tobacco manufacturers and distributors, tobacco growers are not encountering them much these days. Most tobacco is grown under contract, which means that growers grow only the amount they have contracted and do not “carry over” or store tobacco from one year to the next.

According to Bryant Spivey, Johnston County, North Carolina, Extension director, “you would have to go back to the late ’90s to see much tobacco stored on the farm.”

Rick Smith of Independent Leaf Tobacco Company echoes that sentiment. “Nobody carries over any more,” he says. “If they do, it’s an accident.”

Category: Diseases & Pests

About the Author ()

Comments are closed.