Skip to main content

Soft scale insect, repens scale (Pulvinaria rhododendri), on Rhododendron spp. in Northern Europe

Soft scale insect, repens scale (Pulvinaria rhododendri), on Rhododendron spp. in Northern Europe

NEWS - Repens scale (Pulvinaria rhododendri Kahrer & Hodgson, Hemiptera: Coccomorpha: Coccidae) was discovered in Rhododendron spp. (Ericaceae) in Denmark and Norway which appears taxonomically close to P. camelicola Signoret and P. floccifera Westwood with an uncertain geographic origin, but is likely to have been introduced to northern Europe via imported live plants.

P. rhododendri is distinguished from P. floccifera, P. camelicola and all other Pulvinaria species by a combination of characters-a medial band of large conical spinous setae extending from the anal plate anterior to the head and simple pores with strongly sclerotic margins present in a narrow medial band between the large conical spinous setae.

The new species also differs from P. floccifera by the presence of a type III tubular canal submarginally between the lateral stigmatic clefts (vs. absent). The species is named after the genus of the host plant from which it is most commonly collected, Rhododendron L. P. rhododendri is also found on Vaccinium myrtillus L. (Ericaceae) but only when Rhododendron spp. are present nearby.

In Denmark, the species has been found in gardens on the mainland at Hadsund Syd, Jutland, and at Tyfelse on the island of Zealand, 25 km southwest of Copenhagen. These gardens are probably about 150 km apart. In Norway, P. rhododendri has been collected from Arendal and Grimstad on the south coast, about 250 km north of Jutland, Denmark.

The new species is only known from a small area in northern Europe and was probably first found on Rhododendron spp. in Norway in 2018 causing severe sooty mold infestations. This plant was eradicated but the population appears to have persisted as specimens were collected at the same location in 2022.

It is likely that the first discovery also referred to P. rhododendri and since it is still present, it is clearly growing and overwintering under northern European conditions, having survived two winters in between.

To date, no geographical surveys have been carried out to determine the distribution of the species. This host plant could spread more widely as it is cultivated, is a popular plant and is often moved in the plant trade.

The new species is potentially important as a pest of urban plants, especially Rhododendron spp., based on the distribution mentioned above. In the field, P. rhododendri is somewhat similar to P. camelicola which may have been mistaken for non-entomologists in the past.

P. rhododendri, like other Pulvinaria species, produces abundant honeydew, so the growth of sooty mold is a major problem, forming a thick, unsightly layer covering the leaves. However, so far it does not appear to cause host mortality or other problems.

Original research

Andreas Kahrer & Chris J. Hodgson (2024). A new species of the soft scale insect genus Pulvinaria Targioni Tozzetti (Hemiptera: Coccomorpha: Coccidae) on Rhododendron spp. in Northern Europe. Zootaxa 5512 (2): 233-239, DOI:10.11646/zootaxa.5512.2.7

Dlium theDlium
Labels:

Popular Posts

Guinea grass (Panicum maximum)

Guinea grass or buffalo grass or green panic ( Panicum maximum ) is a plant species in Poaceae, annual grasses, growing upright to form clumps, strong, cultivated in all tropical and subtropical regions for very high value as fodder. P. maximum reproduces in very large pols, fibrous roots penetrate into the soil, upright stems, green, 1-1.5 m tall and have smooth cavities for diameters up to 2.5 mm. Propagation is done vegetatively and generatively. Ribbon-shaped leaves with a pointed tip, very many, built in lines, green, 40-105 cm long, 10-30 mm wide, erect, branched, a white linear bone, often covered with a layer of white wax, rough surface by hair short, dense and spread. The flower grows at the end of a long and upright stalk, open with the main axis length to more than 25 cm and the length of the bunches down to 20 cm. Grains have a size of 3x4 mm and oval. Seeds have a length of 2.25-2.50 mm and each 1 kg contains 1.2 - 1.5 million seeds. Guinea grass has two varieties. P...
Read more

Indian shot (Canna indica)

Puspa midra or Indian shot ( Canna indica ) is is plant species in Cannaceae, annual, shrub 0.5-2.5 meters high, depending on variety, erect stems, unbranched and leaf midrib arranged overlapping to form pseudostems and hermaphrodite flowers. C. indica forms a branched rhizome, 60 cm long which is divided into rounded segments and is covered in two stripes by pale green or purple scaly leaves. The rhizome has tubers that contain very large starch grains. The surface has transverse furrows, the underside appears white roots and numerous shoots. The leaves sit alternate and spiral or arranged in two rows, very large and divided into a leaf midrib, short stalk and blade. The strands are 30-60 cm long, 10-20 cm wide and have linear veins, green or purple-green, the base blunt or narrowly pointed and the apex immediately tapering or sharp. Hermaphrodite flowers, pedicels 0.2-1 cm long and red or yellow-orange, except in some cultivars 4.5-7.5 cm long. The sepals are triangular in shape a...
Read more

Indian rosewood (Dalbergia latifolia)

Sonokeling or Java palisandre or Indian rosewood ( Dalbergia latifolia ) is a species of plant in the Fabaceae, a large tree producing hardwood, medium weight and high quality, rounded leaves, thin and broad pods, highly adaptive, grows in dry and rocky landscapes with lots of sunlight. D. latifolia has medium to large size, cylindrical stems, up to 40 m high with a ring of up to 2 m, the bark is brownish gray and slightly cracked longitudinally. The crown is dense, dome-shaped and sheds leaves. The leaves are compound and pinnate oddly with 5-7 strands that have different sizes and appear alternately on the shaft. The leaves are round or elongated in width or heart, the upper surface is green and the surface is pale green. The flowers are small, 0.5-1 cm long and clustered in panicles. The pods are green to brown when ripe and are elongated lanceolate, pointed at the base and tip. The pods have 1-4 seeds which are soft and brownish. Indian rosewood grows at elevations below 600 m,...
Read more