Petunia Insect Damage

Identification

• Petunias attacked by the petunia or tobacco budworm and the serpentine leafminer, cites the University of California Extension. The insects are also a major pest of geranium and nicotiana. The tobacco budworm is native to the United States and is found extensively in the eastern and southwestern regions of the country. The pest is found in the northern regions during summer. Other common host plants of the serpentine leafminer include marigold, chrysanthemum and tomatoes. The pest is common in California and states in the South.

Description

• The adult tobacco budworm is a moth with 1-½ inch wide, light-green wings with light yellow bands. The females lay their eggs on foliage and buds. Emerging larvae come in different colors including red, brown and green. The caterpillars reach maturity in a month and drop to the soil to pupate. There are two generations of the pests every year. Serpentine leafminers are 1/8 inch long flies with black heads and yellow-and-black thoraxes. The white, legless maggots are also 1/8 inch long while the pupae are brown and oval shaped.

Damage

• Serpentine leafminer maggots feed on the foliage and flower tissue. They leave behind white, winding trails. The weakened foliage takes on a speckled look. Cases of severe infestation cause stunted plant growth and defoliation of damaged leaves. Tobacco budworm caterpillars feed on the plants' ovaries and flower buds. Damage causes failure of some flowers to bloom and chewed petals on the flowers that do bloom. Tobacco budworm damage to petunias is so severe in certain areas of the United States that people stopped growing the flower.

Control

• Control the tobacco budworm caterpillar with the use of synthetic pyrethrins or pyrethroid insecticides. Use products containing Bacillus thuringiensis as a biological-control strategy. Some suggested insecticides include cyfluthrin, bifenthrin or permethrin. Planting resistant varieties of petunias avoids problems with serpentine leafminer. Insecticides are not highly effective in controlling the pests. Introduce natural parasites such as parasitic wasps from the Diglyphus genus in infested plants as an effective method of controlling the insects.