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Small white sap sucking scurfy rose scale insects can encrust rose (Rosa) and occasionally blackberry (Rubus fruticosus) stems, giving plants an unhealthy appearance.
Rose scurfy scale on rose
Like all scale insects scurfy rose scale is a true bug that feeds on plant sap. As adults they are immobile and covered in a waxy ‘shell’. Male scales are flat, narrow greyish white scales, up to 1mm in length. Female scales are pear-shaped and up to 2.5mm long. Eggs are laid in July or early August and hatch in August to September.
The crawler nymphs are orange and wonder around on plant material and can be distributed from plant to plant in wind currents. The nymphs soon become sedentary developing into scales. In this species the male scales develop into winged adults in May or June, the females remain under the scale. Mating occurs in May or June.
Scurfy rose scale insect infestations can completely encrust parts of rose stems, giving an unhealthy appearance. Heavy infestations can reduce plant vigour although unlike some other scale insects this species does not produce honeydew.
Scurfy rose scale can be difficult to control, replacing severely infested plants can be considered.
Well-tended healthy plants are usually able to tolerate light infestations. The scales can also be scraped off the stems.
The waxy covering produced by scales gives them some protection from insecticides and the best results are achieved by spraying against the newly hatched crawlers in August or September.
Provided manufactures instructions are followed especially regarding maximum number of sprays and harvest interval infested blackcurrants can be treated with some formulations of deltamethrin, lambda-cyhalothrin and organic products.
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