Lepidosaphes ulmi
Encyclopedia
Lepidosaphes ulmi also known as apple mussel scale or oystershell scale is a scale insect
that is a pest of trees and woody plants. The small insects attach themselves to bark and cause injury by sucking the tree's sap; this metabolic drain on the plant may kill a branch or the entire tree.
shell. The upper side is a banded, brown, waxy scale and the underside is cream coloured. There are no eyes or legs and the short antennae
have only a single segment. The mandibles are lengthened into a stylet adapted for sucking sap. The female lays about one hundred oval white eggs, retaining them under her body, and then dies. Her scale darkens in colour and stays in place, protecting the eggs over the winter. They can survive temperatures as low as -32°C. They hatch in the spring at about the time the host plant's buds are bursting. The crawlers are tiny and disperse on the host, each one looking for a suitable protected site with thin bark in which to settle, remaining in that place permanently after sinking the stylet into the host plant's vascular tissues. The crawler moults twice before becoming an adult female, forming a protective scale from larval exuvia
e and secretions. Some crawlers may develop into males. These undergo four moults and the adult males have eyes, three pairs of legs, one pair of wings, a head and a body divided into a thorax and abdomen. Not all colonies produce males and bisexual and parthenogenetic populations are known.
, Betulaceae
, Caprifoliaceae
, Celastraceae
, Elaeagnaceae
, Grossulariaceae, Hydrangeaceae
, Juglandaceae
, Oleaceae
, Pyrolaceae
, Rosaceae
, Salicaceae
and Tiliaceae
. Apart from forest trees and ornamentals, the oystershell scale is a pest of apples, pears, plums, peaches, apricots, mulberries and currants. It infests trunks and branches but is not found on leaves. Heavy infestations can kill branches and even cause trees to die.
s but adult oystershell scales are protected by their waxy scales which repel water. Use of horticultural oil
s may overcome this problem but control is still difficult. In gardens, trunks and branches may be scrubbed and heavily infested wood pruned out and removed. In some parts of the world, populations are controlled to a certain extent by the oystershell scale parasitoid
, Aphytis mytilaspidis
and the ladybird Chilocorus bipustulatus
.
Scale insect
The scale insects are small insects of the order Hemiptera, generally classified as the superfamily Coccoidea. There are about 8,000 species of scale insects.-Ecology:...
that is a pest of trees and woody plants. The small insects attach themselves to bark and cause injury by sucking the tree's sap; this metabolic drain on the plant may kill a branch or the entire tree.
Biology
The adult female oystershell scale is up to four millimetres long, elongated, tapering to a point at the posterior end and often slightly curved, somewhat resembling a musselMussel
The common name mussel is used for members of several families of clams or bivalvia mollusca, from saltwater and freshwater habitats. These groups have in common a shell whose outline is elongated and asymmetrical compared with other edible clams, which are often more or less rounded or oval.The...
shell. The upper side is a banded, brown, waxy scale and the underside is cream coloured. There are no eyes or legs and the short antennae
Antenna (biology)
Antennae in biology have historically been paired appendages used for sensing in arthropods. More recently, the term has also been applied to cilium structures present in most cell types of eukaryotes....
have only a single segment. The mandibles are lengthened into a stylet adapted for sucking sap. The female lays about one hundred oval white eggs, retaining them under her body, and then dies. Her scale darkens in colour and stays in place, protecting the eggs over the winter. They can survive temperatures as low as -32°C. They hatch in the spring at about the time the host plant's buds are bursting. The crawlers are tiny and disperse on the host, each one looking for a suitable protected site with thin bark in which to settle, remaining in that place permanently after sinking the stylet into the host plant's vascular tissues. The crawler moults twice before becoming an adult female, forming a protective scale from larval exuvia
Exuvia
Exuviae is a term used in biology to describe the remains of an exoskeleton and related structures that are left after ecdysozoans have moulted...
e and secretions. Some crawlers may develop into males. These undergo four moults and the adult males have eyes, three pairs of legs, one pair of wings, a head and a body divided into a thorax and abdomen. Not all colonies produce males and bisexual and parthenogenetic populations are known.
Host plants
Over one hundred and fifty host plant species are known for the oystershell scale including members of the families AceraceaeAceraceae
Aceraceae is a family of flowering plants also called the Maple Family. It contains two to four genera, depending upon the circumscription, of some 120 species of trees and shrubs. A common characteristic is that the leaves are opposite, and the fruit a schizocarp.The maples have long been known...
, Betulaceae
Betulaceae
Betulaceae, or the Birch Family, includes six genera of deciduous nut-bearing trees and shrubs, including the birches, alders, hazels, hornbeams and hop-hornbeams, numbering about 130 species...
, Caprifoliaceae
Caprifoliaceae
The Caprifoliaceae or honeysuckle family is a clade consisting of about 800 dicotyledonous flowering plants, with a nearly cosmopolitan distribution; centres of diversity are found in eastern North America and eastern Asia, while they are absent in tropical and southern Africa.They are mostly...
, Celastraceae
Celastraceae
The Celastraceae , is a family of about 90-100 genera and 1,300 species of vines, shrubs and small trees, belonging to the order Celastrales...
, Elaeagnaceae
Elaeagnaceae
Elaeagnaceae, the oleaster family, is a plant family of the order Rosales comprising small trees and shrubs, native to temperate regions of the Northern Hemisphere, south into tropical Asia and Australia. The family has 45-50 species in three genera....
, Grossulariaceae, Hydrangeaceae
Hydrangeaceae
Hydrangeaceae are a family of flowering plants in the order Cornales, with a wide distribution in Asia and North America, and locally in southeastern Europe.-Overview:...
, Juglandaceae
Juglandaceae
The Juglandaceae, also known as the Walnut Family, is a family of trees, or sometimes shrubs, in the order Fagales. Various members of this family are native to the Americas, Eurasia, and Southeast Asia....
, Oleaceae
Oleaceae
Oleaceae are a family containing 24 extant genera and around 600 species of mesophytic shrubs, trees and occasionally vines. As shrubs, members of this family may be twine climbers, or scramblers.-Leaves:...
, Pyrolaceae
Pyrolaceae
Pyrolaceae was a small family of flowering plants under the old Cronquist system of plant classification. It included the four genera Chimaphila, Moneses, Orthilia, and Pyrola, and sometimes also the eight genera formerly usually placed in the family Monotropaceae.Recent genetic research by the...
, Rosaceae
Rosaceae
Rosaceae are a medium-sized family of flowering plants, including about 2830 species in 95 genera. The name is derived from the type genus Rosa. Among the largest genera are Alchemilla , Sorbus , Crataegus , Cotoneaster , and Rubus...
, Salicaceae
Salicaceae
Salicaceae are a family of flowering plants. Recent genetic studies summarized by the Angiosperm Phylogeny Group has greatly expanded the circumscription of the family to contain 55 genera....
and Tiliaceae
Tiliaceae
Tiliaceae is a botanical name for a family of flowering plants. Such a family is not part of APG II, but it is found all through the botanical literature and remains prominently listed by nomenclatural databases such as IPNI....
. Apart from forest trees and ornamentals, the oystershell scale is a pest of apples, pears, plums, peaches, apricots, mulberries and currants. It infests trunks and branches but is not found on leaves. Heavy infestations can kill branches and even cause trees to die.
Control
The crawlers are vulnerable to a number of pesticidePesticide
Pesticides are substances or mixture of substances intended for preventing, destroying, repelling or mitigating any pest.A pesticide may be a chemical unicycle, biological agent , antimicrobial, disinfectant or device used against any pest...
s but adult oystershell scales are protected by their waxy scales which repel water. Use of horticultural oil
Horticultural oil
Horticultural Oils or Narrow Range Oils are lightweight oils, either petroleum or vegetable based. They are used in both horticulture and agriculture, where they are applied as a dilute spray on plant surfaces to control insects and mites...
s may overcome this problem but control is still difficult. In gardens, trunks and branches may be scrubbed and heavily infested wood pruned out and removed. In some parts of the world, populations are controlled to a certain extent by the oystershell scale parasitoid
Parasitoid
A parasitoid is an organism that spends a significant portion of its life history attached to or within a single host organism in a relationship that is in essence parasitic; unlike a true parasite, however, it ultimately sterilises or kills, and sometimes consumes, the host...
, Aphytis mytilaspidis
Aphytis mytilaspidis
Aphytis mytilaspidis is a species of chalcid wasp in the Aphelinidae family. The adults feed on scale insects and the larvae are ectoparasites of scales.-Distribution:...
and the ladybird Chilocorus bipustulatus
Chilocorus bipustulatus
Chilocorus bipustulatus, the heather ladybird, is a beetle species belonging to the family Coccinellidae, subfamily Chilocorinae.These beetles are found in most of Europe, in East Palearctic ecozone, in the Near East and in North Africa....
.