Start your aphid battle the natural way:
Plant sweet alyssum in the flower garden to draw beneficial wasps. Include cosmos to attract hungry lacewings, and add penstemon or yarrow to attract ladybugs. Insect soap and a strong blast of water will take care of heavy infestations. Encourage ladybugs in your garden. A single ladybug can eat as many as 5,000 aphids in its one-year lifespan and larvae eat hundreds before they pupate.
The worst borer in the flower garden is the iris borer, which will tunnel through an entire iris rhizome, leaving bacterial rot in its wake. You should be suspicious if you notice sawdust material around the base of your irises or ragged leaf margins. Pinprick holes in the leaves of iris are the signs of tiny caterpillars that have infiltrated the leaves and are making their way down into the rhizomes.
Discourage borers by removing iris leaves in the fall, which provide a host for borer moth eggs. In the spring, you can apply the systemic pesticide Merit or the nontoxic spray Garden Shield. The best non-toxic control is to dig up affected plants after flowering is done, trim out the rotten rhizomes, and replant the good portions.
Remove debris from the garden at the end of the season to eliminate overwintering sites. Use floating row covers to prevent leafhoppers from reaching your plants. Blast leafhopper nymphs from plants with a strong jet of water. Spray adults with insect soap, pyrethrin, or Sevin. Keep dandelion and thistle weeds away from the flower garden, as they provide cover for leafhoppers. Encourage beneficial insects, such as ladybugs, lacewings, and pirate bugs, which all prey on the eggs and larvae of leafhoppers.
If you notice white fuzzy growths on your plants, you may have mealybugs. Ways to control mealybugs include:
Avoid overwatering and over fertilizing since mealybugs are attracted to new growth and plants with high levels of nitrogen. Dip a cotton swab in rubbing alcohol and touch it to the pests to desiccate and kill them instantly. You can also spray the pests away with water, or apply Malathion or Orthene pesticide sprays. Use insecticidal soap or neem oil as repellants; these products do not harm honeybees and other beneficial insects. Encourage beneficial insects, such as ladybugs and lacewings, which are predators of mealybugs.
Like leafhoppers, plant bugs inject a toxin into your plants’ leaves, buds, and shoots as they feed. The result is a plant mottled with brown or black spots and deformed growth. Dahlias, azaleas, daisies, Liatris, and asters are just a few of the flowering plants these bugs commonly feast upon. Gardeners should be on the lookout for tarnished plant bugs and four-lined plant bugs, growing up to a 1/4 inch long. Plant bugs often have an unpleasant odor.
Plant bugs are fast moving pests, but you can pluck them off and drop them into a bucket of soapy water if you’re an early riser, as the bugs are sluggish in the morning. Spraying young bugs with neem oil or insecticidal soap will offer some control for most plant bugs. Protecting edible crops with floating row covers will prevent plant bugs from damaging your vegetables. Plant bugs can be killed by spraying your plants with neem, Sevin, or diazinon. Use sparingly, as these chemicals will also kill beneficial insects.
Parasitic wasps love to use scale insects as hosts, and you may see evidence of this as tiny holes piercing the scale’s armor. This same armor makes scale resistant to many pesticides, but dormant oil can suffocate the insects during the winter season. To control scale:
Dispose of affected branches and leaves, which harbor the insects. Pick off the insects by hand—a viable solution if the numbers are low. Dab individual insects with a cotton swab dipped in rubbing alcohol.Encourage beneficial insects such as ladybugs and lacewings, which feed on scale insects. Use insecticidal soap or oils to coat scale. This will require repeated applications but is very safe for the environment. Apply neem oil to affected plants. A concentrated form of neem oil, azadirachtin, is a very effective control. If chemicals are needed, those containing acephate or imidacloprid are effective as systemic pesticides.
Take advantage of the small size and weakness of these insects by using a vacuum to remove them from plants. Yellow sticky traps can be used to trap adult whiteflies. Encourage natural predators such as ladybugs and lacewings. Insecticidal soaps work well on heavy infestations but must be applied regularly. Neem oil and other horticultural oils will kill whiteflies; make sure to completely drench plants. Where chemical pesticides are needed, use natural insecticides containing pyrethrin. Malathion is a more aggressive chemical that can be used sparingly.
