What's Bugging Your Annuals
Insect Pests
Aphids
Plants Affected: Numerous indoor and outdoor plants
Symptoms: Severe infestations will cause curling/twisting of foliage, flowers to wilt and drop
Life Cycle: Eggs hatch on host plants in spring, these nymphs give birth to ‘daughters’, within days the daughters give birth – up to 30 generations per summer
Cultural Control:
• Ladybird beetles/larvae, lacewings are natural predators
• Strong jet of water to knock aphids off plants
Chemical Control: Doktor Doom House and Garden, End All
Flea Beetles
Plants Affected: Numerous annuals and perennials
Symptoms: Numerous holes in foliage, about the size of a pinhead
Life Cycle: Overwinter in soil beneath leaf debris, emerge in spring. Adults feed on foliage, mate and lay eggs
Controls – Cultural or Non-chemical: Clean up leaf debris and weeds in autumn
Controls – Chemical: Spray adult beetles in spring before they lay eggs; Ambush, Dr. Doom House and Garden
Slugs
Plants Affected: Annuals and perennials
Symptoms: Ragged holes chewed in leaves, slime trails on leaves
Life Cycle:
•Overwinter as eggs in soil
• Hermaphrodite; every slug can lay eggs. Eggs laid in batches of 10-0 in moist soil
Controls – Cultural or Non-chemical:
• Till soil to disturb eggs, expose eggs to natural predators
• Spread Diatomaceous earth or other gritty substances under plant leaves
• Spread iron based slug pellets (Sluggo or Safer’s) at base of plants, under foliage
• Beer traps, dishes filled with beer, set at soil level, may attract and drown slugs
Controls – Chemical: Metaldehyde based pellets
Spider Mites
Plants Affected: Numerous indoor and outdoor plants
Symptoms:
• Stippling—tiny dots in foliage
• Yellowing of foliage—’haze’ on foliage
Life Cycle:
• Can overwinter in various stages under debris or bark on host plants, in greenhouses
• Become active in spring as foliage emerges
Cultural Control:
• Lacewings are natural predators
• Keep plants misted (they prefer dry conditions)
• Fall debris cleanup
Chemical Control: End All, Doktor Doom House and Garden
Diseases
Leaf Spot on Roses
Plants Affected: Roses
Symptoms: Black spots appear on upper leaf surfaces, leaves eventually drop
Life Cycle:
• Overwinters in diseased canes and leaf debris beneath plants
• In spring, spores are spread by splashing water/rain. Fungal spores require 7 hours of moisture for infection to occur. Once infection occurs black spots start to develop
Cultural Control:
• Remove diseased leaves
• Prune roses to ensure good air circulation, do not water foliage (water base of plant)
Chemical Control: Garden Sulphur applied as preventative every 7-10 days
Powdery Mildew
Plants Affected: Many perennials and annuals, popular hosts include garden phlox, speedwell, salvia, begonias, impatiens
Symptoms :
• White powdery spots, yellowing leaves
• Plants cannot manufacture as much food as they need – severe infestations will kill plants such as begonia
Life Cycle: Specific spores (black spherical ones) overwinter on leaf debris and soil. High humidity favours spore production, while low humidity favours spore maturation and release
Cultural Control:
• Good circulation, full sun
• Clean up debris in fall
Chemical Controls: Garden Sulphur applied as preventative every 7-10 days
Rust
Plants Affected: Perennials, roses
Symptoms :
• Reddish orange spots on leaves and stems
• Wilting and defoliation follows
Life Cycle: Spores overwinter on leaf debris and any dead/dying canes
Cultural Control: Prune out, good fall cleanup
Chemical Controls: Garden Sulphur applied as preventative every 7-10 days
Cultural Disorders
Chlorosis
Symptoms:
• leaves are yellow but veins remain green, may be some browning on the margins of leaves
• will be evident first on new growth, then work back to older leaves on a branch
Control:
• ensure loose, well-drained soil, avoid overwatering
• high soil alkalinity can also be a cause, plants can be fertilized with iron chelate for recovery
Herbicide Damage
Symptoms:
• curling or cupping leaves
• discoloration between veins
• twisted, elongated stems
Control:
• use all herbicides according to label, note that herbicide can drift for several miles, it’s very difficult to ascertain where chemical drifts from
• keep damaged plants well-watered, most plants will recover
Overwatering
Symptoms:
• wilting, yellowing leaves
• leaves will yellow from outside in
• Note: wilting is a symptom of BOTH over and underwatering, if plants are wilting don’t assume they require moisture until soil is checked by hand
Controls:
• plants in lower lying areas will suffer in times of heavy rains; plant appropriate species in these areas
• for new and established plants, water only as required; check soil prior to watering
Underwatering
Symptoms:
• wilting, crispy or browned leaf edges
Controls:
• water, especially for new transplants should be monitored daily during periods of extreme heat
• for new transplants, stick your hand into the soil to determine if moisture is required