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Annual Pests: Typical Symptoms, Causes and Cures

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Patricia Freeman

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Aphids On Annual Bloom
Photo Credit: ©2000 Dolezal Publishing/John M. Rickard
Aphids are sucking insects that feed on plant juices. As a first defense, blast them off your plants with a strong stream of water from the garden hose.

The best way to defend against pest invasion in annual gardens is to start planting beds off right – from amending the soil and choosing healthy plants to proper planting technique. Unfortunately, sometimes our best efforts are no match for “bad bugs.”

Is your flower garden under attack? Use this guide to help identify common pest-problem symptoms on annuals, learn which pest is likely causing the issue and discover some remedies to try.

Symptom: Curled, puckered or twisted leaves, often with a sticky coating and/or black, sooty appearance. Stunted or deformed blooms on new growth.

Cause: Aphids. Look for tiny, green-yellow, reddish, brown or gray wingless insects clustered on buds, shoots and undersides of leaves.

Remedies: Spray with a strong stream of water from the garden hose, try insecticidal soap or remove and discard plants.

Symptom: Seedlings cut off at ground level.

Cause: Cutworms. Look for smooth, gray-brown, wormlike moth larvae under plant debris or just below the soil surface.

Remedies: Install cardboard collars (like toilet paper tubes) around plant stems and sink them 2 inches into the soil.

Symptom: Holes in leaves and flowers. Stems may be reduced to skeletons.

Cause: Japanese beetles. Look for half-inch-long insects with copper-colored bodies and green heads.

Remedies: Handpick, then kill the pests by either stomping on them or dropping them in a bucket of soapy water. Spray with insecticidal soap near soil. If that’s ineffective in controlling the infestation, spray insects with pyrethrin or rotenone, but only as a last resort.

Symptom: Leaves stippled with yellow; may be curled, dry and withered, with webs on tips and undersides. Plant may be stunted.

Cause: Spider mites. Look for reddish, green or yellow, pinhead-sized insects. Prevalent in hot, dry areas. (Lantana, hollyhock, verbena and sweetpea are particularly susceptible.)

Remedies: Spray with a steady stream of water or try insecticidal soap. If both are ineffective, spray with Neem or pyrethrin, but only as a last resort.

Symptom: Yellow leaves and stunted, sticky plants. When plant is shaken, a cloud of white insects may fly up.

Cause: Whiteflies. Look for minuscule, white, mothlike insects on the undersides of leaves.

Remedies: Catch with sticky cards, or try insecticidal soap. Horticultural oil may also work. If infestation continues, spray with pyrethrin, but only as a last resort.

Warnings
  • Many naturally-derived garden products are also toxic. No matter what type of pesticide or garden chemical you may be considering, always read the label first!
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Facts
  • Contrary to what you may have heard, kitchen soap is not an effective form of pest control – but insecticidal soap is. Yet, as great as they are, insecticidal soaps are not a cure-all – they do have limitations. One of the biggest is that the soap must come in direct contact with the pest in order for the product to kill.
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  • Insects can bug you in the garden, but don’t automatically reach for the chemicals. Remember, some insects are actually beneficial to your garden! You can help reduce populations of unwanted pests by practicing integrated pest management – or IPM. Several methods are commonly used, including inspecting plants for pests, growing pest-resistant plant varieties and implementing good cultural practices in the garden. When enforcing IPM, pesticides are only used as a last resort.
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Tips
  • Whenever you opt to use control products in your garden, restrict their application to only the infested area. Spray on a wind-free, cool day, wearing a respirator and protective clothing, and strictly follow all label instructions.
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Resources
 
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