Hawthorn Lace Bug

Causal Organism: Corythucha cydonidae

Crops Affected: Saskatoon berry and other plants in the Rose family (apples, crabapples, hawthorn, pear, cotoneaster, mountain ash, etc.)

Life Cycle:

• This pest belongs to a small group of insects (Tingidae) within the much larger family of True bugs (Hemiptera)
• Lace bugs are often quite host specific, but this specific species has a wide host range
• Adults are a small, delicate-looking insect, which appears to be covered with lace
  • Adults reach about 5mm (3/16 inches) long
  • They have a mottled colour mix, ranging from almost clear and creamy to light browns, with a brown crossbar pattern across their wings
• Eggs are laid in clusters on the undersides of leaves in early spring
  • Eggs are smooth, whitish ovals, with a broader base and a cut off upper end, which is somewhat brown
• Nymphs are somewhat smaller than the adults
  • Nymphs are oval-shaped, flat, dark coloured and have an armoured/spiny appearance
  • Nymphs emerge and feed on the underside of the leaves after about 3 weeks
    • Nymphs pass through 5 instars
  • Both adults and nymphs live on the underside of the leaves, feeding by piercing leaves and sucking out plant juices
  • HLB overwinters as adults, typically in leaf litter and other protected areas near their host plants
    • There can be up to two generations per season
    • The first generation of adults emerge in midsummer
      • The second generation emerges in fall
    • Multiple life stages will be visible on a plant at a given time

Symptoms:

• Feeding by adults and nymphs (by piercing and sucking) leaves tiny yellow/white coloured spots
  • The upper side of the leaves will develop a stippled or mottled appearance, with the degree of damage increasing according to the number of lace bugs that are present
• HLB tends to feed in large numbers
  • Leaves may be stained with their excrement (poop)
  • This is evident as tiny black/brown tar-like blobs scattered around the feeding adults and nymphs
• The leaves may be crowded with several adults and nymphs
• In heavy infestations, premature leaf drop may be observed
  • Branch dieback and plant death has been reported in other areas, but is uncommon in Alberta

Monitoring:

• This not required, but HLB can be detected while scouting for other insect pests

Management:

• Not typically required, as this pest does not typically cause economic damage
  • It is more a nuisance pest, producing cosmetic damage and reducing aesthetic value of plants
  • In some cases, the presence of the pests, along with their poop, can be off-putting for pickers of fruit
• Applying a high-pressure spray of water can dislodge the various life stage, reducing damage
• Broad-spectrum chemical applications for other registered pests might provide some control
  • The use of insecticidal soaps and horticultural oils may be effective at reducing the pest population provided there is good contact between the product and the pest