It is simple: I grow flowers in my garden because they are pretty and colorful. It is disappointing when insects damage or destroy these blossoms. Here are three dastardly pests that are significantly impairing beautiful blooms in my garden.
▪ Thrips: Western flower thrips cause damage to roses and other flowering perennials. Thrips are tiny, straw-colored insects that feed on flower petals, often before the buds even open. They use their rasping mouths to scrape at plant tissues and suck up the liquids that ooze out. Their feeding causes streaks and blotches on the petals. If damage is severe, the flower buds may fail to open.
Thrips are difficult to control because their populations build up quickly. Prune off and dispose of badly infested flowers and buds. Eliminate plant litter and weeds in and around the garden. Avoid using pesticides that kill thrips predators, like lady beetles and lacewings, or that harm bees visiting the flowers. If you decide to apply an insecticide, apply it directly the buds and blooms. Repeat applications are likely to be needed. For effective insecticides, go to bit.ly/thripinsecticides.
▪ Tobacco budworm: The tobacco budworm is devouring all the buds on my petunias, including my beloved Wave petunias, before they even have a chance to open. Aargh! The few flowers that are able to open are riddled with holes. The adult tobacco budworm is an unremarkable greenish-brown moth about three-fourth-inch long. Like many moths, it is nocturnal, flying, mating and laying eggs at night, starting in late spring to early summer.
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On petunias, the moths typically lay their eggs on the leaves, but on geraniums, they deposit them directly on the flower bud clusters. As soon as the eggs hatch, the little larvae immediately get to work eating flower buds. They will also eat holes in leaves, especially when there are not many flower buds left. Along with the obvious holes in flower petals, buds and leaves, they deposit their telltale small black frass (poop) on the leaves.
Tobacco budworm also feeds on many other hosts, such as roses, snapdragon, zinnia, verbena, chrysanthemum, marigold and sunflower. However, its preferred hosts are petunias and geraniums.
The larvae are hard to detect because young larvae are yellowish-green and blend in well with foliage. More mature larvae vary in color from green to brown, tan or purple. During the day, the larvae tend to hide in the soil at the base of the plant and then venture out at dusk to feed. When using hand picking for control, look for them at dusk.
As the name infers, tobacco budworm is a pest of tobacco, but it also feeds on many other hosts, such as roses, snapdragon, zinnia, verbena, chrysanthemum, marigold and sunflower. However, its preferred hosts are petunias and geraniums.
▪ Sunflower moth: The larvae of the sunflower moth also attacks garden flowers. Its hosts are sunflowers and other members of the same family, such as daisies, zinnia, coneflower and cosmos. The larvae of the sunflower moth feed on the flower centers, eating the developing seeds and leaving webbing and frass .
Most home garden insecticides are ineffective against both the tobacco budworm and the sunflower moth. For effective insecticides, go to bit.ly/sunflowermoth.
When using insecticides for control of tobacco budworms, apply them as soon as feeding damage is noticed. For sunflower moths, apply them when the flowers start to bloom.
I do not like using insecticides in my garden, especially on flowers that are visited by bees and other pollinating insects. As a result, I have switched to plants planted for the colorful foliage, like coleus and sweet potato, but I just cannot give up my petunias.
Marianne C. Ophardt is a horticulturist for Washington State University Benton County Extension.