Rose scale

Rose scale Aulacaspis rosae
Appearance:

An attack by rose scale Aulacaspis rosae is being recognized due to the presence of spots with a white, peel-like structure. These places are often found on the stem of a shrub, quite hidden in the bottom of the crop. Within the rose scale, the males are clearly different from the females. Both have a light dirty white to white color; Females are more or less round whereas males are elongated. The females that live protected under the light-colored shield have an orange body. Even the youngest instars that are still below the mother's scale cover are orange in color. Once they are settled on the plant, most of the time near to the mother, they start preparing the light-colored scale cover. The rest of their lives they will stay at this place, hidden beneath the scale cover and do not move anymore. The males grow up in an elongated white-ribbed cocoon. As soon as they are full grown, they come out of it. Then they are far different from the females, winged and very tiny. They can fly a short distance to find a female for mating. The color of their body is like the one from the females, orange.

Damage from rose scale:

Rose growers are very keen on recognizing the presence of rose scale in a very early stage. Out of experience they know that rose scale is sometimes only noticed until the infestation is already rather serious. Larger areas with a high density of scales cover the stems and young crawlers disperse themselves along the tribes to adjacent shrubs. Such heavy attacks cause big damage: the rose shrubs become completely  covered by the scales who suck from stems and leaves. Wilting, shriveling and leaf drop occurs and at the end reduced shoot and flower formation. Ultimately, plants can die completely due to such infestation.

Aulacaspis rosae

Biocontrol agents:

Against rose scale in particular the coccinellid predator Rhyzobius lophanthae is effective as a biological control agent. Settlement of this species is not always easy, often due to residues of pesticides but if this predator gets the opportunity to build up a population it will finally clean up the infestation. Moreover at sites where growers make the decision to choose a biological / integrated approach and start introducing Rhyzobius lophanthae, we often see spontaneously 2 native parasitoid species parasitizing the scales in the greenhouse: Arrhenophagus and Adelencyrtus. These seem to come from outside the greenhouse and seriously contribute to the biological control of the rose scale.

life cycle rose scale:

  • Development time is 1 to 3 months
  • In winter hardly any development
  • Female may lay 100-200 eggs
  • Bigger part of young crawlers dies
  • In greenhouses several generations per year

host plants of rose scale:

  • roses
  • Rubus, berries
  • Hydrangea
  • Pyrus

PRODUCTS AGAINST ROSE SCALE:

Karnyothrips melaleucus:

K. melaleucus

Rhyzobius lophanthae:

R. lophanthae