Tobacco Flea Beetles & Hornworms

Flea Beetles

Tobacco flea beetles (Figure 1) usually are a common problem right after tobacco is transplanted. Overwintered adults fly into fields to feed before laying eggs around the base of newly-set tobacco and other solanaceous plants. Flea beetle larvae feed on tobacco roots and emerge as adults about 30 days later. There are three or more generations each year but systemic insecticides applied at transplanting usually provide satisfactory control.

Occasionally, tobacco flea beetles can cause significant damage (Figure 2) late in the season.  These small, hopping insects chew small round holes almost completely through leaves. Often, there is a brown rim around their feeding holes. Damage begins on the lower leaves with the beetles working their way up plants as leaves become tattered from their feeding.  Flea beetle damage is usually uniformly spread across fields.  The treatment guideline for this insect is an average of 60 or more beetles per plant

Figure 1. Tobacco flea beetle (Photo: Brandon Bell, Metcalfe County Extension Agent)

Figure 1. Tobacco flea beetle (Photo: Brandon Bell, Metcalfe County Extension Agent)

Figure 2. Severe late season tobacco flea beetle damage (Photo: Lee Townsend, UK)

Figure 2. Severe late season tobacco flea beetle damage (Photo: Lee Townsend, UK)

Tobacco Hornworms

Tobacco hornworms are active now, too. Newly hatched hornworms chew larger holes in leaves (Figure 3) than those caused by flea beetles and they usually have cleaner margins. Also, small hornworms usually can be found in the underside of damaged leaves. Treatment guidelines for this insect are 5 or more live worms per 50 plants (do not count hornworms with white cocoons on their backs, Figure 4).)

Figure 3. Feeding by small tobacco hornworms usually occurs on the upper 1/3 of plants (Photo: Lee Townsend, UK).

Figure 3. Feeding by small tobacco hornworms usually occurs on the upper 1/3 of plants (Photo: Lee Townsend, UK).

Figure 4. Do not count hornworms with silken wasp cocoons on their backs when assessing infestations (Photo: Lee Towsend, UK).

Figure 4. Do not count hornworms with silken wasp cocoons on their backs when assessing infestations (Photo: Lee Towsend, UK).

Management

The following insecticides are labeled for flea beetle and hornworm control on tobacco:

  • Assail (acetamiprid) – REI 12 hours , harvest 7 days
  • Carbaryl 4L – REI 48 hours, harvest 2 days
  • Voliam Flexi (thiamethoxam + chlorantraniliprole) – REI 12 hours, harvest 14 days.

Do not apply these products while bees are actively visiting the treatment area. Voliam Flexi has a pollinator warning on the label. Bees and other insect pollinators can be exposed to this pesticide from:

  • Direct contact during foliar applications, or contact with residues on plant surfaces after foliar applications
  • Ingestion of residues in nectar and pollen when the pesticide is applied as a seed treatment, soil, tree injection, as well as foliar applications.

 

By Lee Townsend, Extension Entomologist

 

Posted in Tobacco