"Budworm Control in Flue-Cured Tobacco" Mitch Smith, County Extension Director Pitt County Extension Center Greenville, NC 27834

Introduction

In 2000, 59 percent of Pitt County tobacco producers treated for the control of budworms. With such a wide range of control, growers may often be uncertain as to whether treatment should be made to control this tobacco pest. The purpose of this fact sheet is to provide helpful tips regarding this important management decision.

Scouting

The decision to treat for budworms should only be based on an effective scouting program. Many farmers do not notice budworms in the crop until damage is easily seen. By this time, fields may have been above threshold for several days.

Scouting for budworms should begin no later than three to four weeks after transplanting and in those fields which were planted the earliest. These fields tend to be the most attractive to the budworm moth (adults). When scouting, the effort should be made to look in the bud and on both sides of the leaf.

Budworm Lifecycle

Tobacco in eastern North Carolina may experience damage from both corn earworms and budworms with budworms being the most common.

Tobacco budworm adults emerge from late April to mid-May. Corn earworms adults emerge from early May to early June. Egg-laying moths are most attracted to the flowers of tops and to the tallest tobacco plants.

Once the moth reaches the tobacco plant, eggs are deposited on the leaves or the bud of the tobacco plant. After 24 hours, eggs hatch and larvae may first feed on the leaf and then move to the bud region.

Once the budworm completes it's development as a larva (which is a caterpillar) it drops to the ground, wanders around a bit and tunnels into the soil. In the soil it transforms into a pupa and then into an adult moth. This takes a little over two weeks. The moth then tunnels back up to the surface, finds a mate and begins the cycle over again. Both species have four generations in North Carolina. Budworms overwinter as pupae in the top 2-4 inches of soil.

Treatment

The economic threshold to justify treatment for budworms is when 10% of plants are infested with "live" budworms of any size prior to buttoning. Budworms will not cause loss of any importance after the plant has buttoned. The decision to spray should be based on the presence of live worms and not damage.

When the level of infestation has reached ten percent, spray applications should be made in the early morning or at night when the bud area of the tobacco plant is the most open. Only one application is usually justified due to the difficulty of control.

Nozzle Selection

Under normal growing conditions, the most common spray nozzle arrangement for budworm control is a three-nozzle rig which has two TX-8 nozzles on the outside and a TX-12 or TX-14 nozzle in the middle. These are hollow cone nozzles resembling a standard sucker control rig with a shorter width.

The spray rig should be centered about 6 inches above the bud. The upper one-third of the plant should receive this application with a high volume of water (25 to 50 gallons per acre).

To utilize existing sucker control rigs, growers can turn the rig to a 45 degree angle to the row in order to reduce the width of treatment. For more irregular rows, turning the nozzles by 30 percent is advisable versus 50 percent (45 degrees).

Dry Weather

Dry weather will make the effective control of budworms more difficult. In dry weather, control with conventional sprays may not exceed 50-60% control versus 70 percent or higher under normal conditions.

Under dry conditions, growers should consider changing their three nozzle arrangements in order to improve control. In this situation, it is advisable to switch to two TG2 nozzles (one at each end)and a TG3 nozzle in the center. These nozzles are solid cone nozzles which provide larger droplets thus allowing greater access to the insect.

Product Selection

While most producers attempt to control budworms with sprays, "baits" provide the most effective control. In on-farms tests over the years, baits have provided 95 percent control compared to 70 percent with sprays.

For spray applications, Tracer can be expected to provide 80-85% control of budworms. Denin and Lannate generally performs equivalent to Tracer but may be less consistent. Admire, which is used in the greenhouse as a tray drench treatment, is not considered to be effective in preventing budworms. Tobacco which has received an application of Admire should be scouted closely for aphids throughout the growing season.

Treatment Recommendations

Because tobacco can compensate for high levels of leaf damage, budworms often cause less yield loss than expected. In on-farm tests from 1998 and 1999, budworm infestation levels of 40 percent (1998) and 100 percent (1999) did not reduce yields compared to tobacco which was kept "budworm free". Therefore, if a crop is experiencing good growth at 4-8 weeks after transplanting, growers may expect limited economic loss due to budworms. At a minimum, if growth is good, growers should not spray unless infestations are greater than 10%.

Disclaimer: The use of brand names in this publication does not imply endorsement of the products or services named or criticism of similar ones not mentioned.

Special thanks to Dr. Sterling Southern, NCSU Extension Entomologist for his contribution to this fact sheet.

Distributed in furtherance of the Acts of Congress of May 8 and June 30, 1914. Employment and program opportunities are offered to all people regardless of race, color, national origin, sex, age, or disability. North Carolina State University at Raleigh, North Carolina A&T State University, U.S. Department of Agriculture, and local governments cooperating.