Petunia Flowers Eaten-up?

This could be the insect eating your Petunias

By: Sandy Feather 2007
Penn State Extension

Q. I have a hanging basket of white petunias that were just lovely. Little by little, it seems that something is eating the flowers. It started out with holes in the petals. Now, a lot of the blooms are gone. I have had rabbits eat petunias in the past, but these are in hanging baskets. Besides, only the flowers are bothered. The plants themselves seem to be unscathed. Do you have any idea what could cause this and what I can do about it?

A. It sounds like the work of the tobacco budworm larva (Heliothis virescens). The larva, or caterpillar, matures at about an 1 1/4 inches long. The larva's color depends somewhat on its diet and varies from black to pale brown, reddish or greenish. This pest can also damage flowering tobacco (Nicotiana spp.), geraniums (Pelargonium spp.), ageratum, snapdragons (Antirrhinum majus), roses, strawflower (Bracteantha bracteata) and many other species of flowers.

Life Cycle of Tobacco Budworm

They overwinter as pupae a few inches below the soil surface near susceptible plants. Adult moths emerge in the spring, and after mating, females lay eggs on host plants. The adult moths are pale green with four lighter, wavy bands on the forewing, and have a wingspan of an 1 1/2 inches or so. Because moths are active at night, you probably would not notice their activity.

Purple petunia hanging basket

The caterpillars hatch and feed primarily on buds and flowers; they rarely feed on leaves. They can cause extensive injury if populations are high. They mature in about three weeks, and then burrow into the soil to pupate. We have two generations in our area every year, with their peak populations occurring in August and early September.


Hand-Pick Budworm Caterpillars

Handpicking is an effective control for small plantings, such as a hanging basket. If the caterpillars make you squeamish, wear gloves to pick them and crush them under foot. Because they are the larvae of moths, Bt (Bacillius thuringiensis) provides good control on small larvae. Bt is a bacterial disease that affects only the larvae of moths and butterflies that feed on treated crops. The target insect must ingest Bt in order for it to work, so plants have to sustain a little more damage. It is very safe for people, pets, wildlife and insects that are not feeding on sprayed plants.

Other Methods of Control

Once the larvae get beyond the half-inch size, Bayer Advanced Power Force Multi-Insect Killer (cyfluthrin) will provide better control. Cyfluthrin is a synthetic form of pyrethrins, a botanical insecticide made from the flowers of the pyrethrum chrysanthemum.


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