HMSO £3.50 Forestry Commission Bulletin Forestry Commission ARCHIVE Conifer Lachnids C I Carter N R Maslen Cover: Top: Colony of Cinara piceae on the stem of pole stage Norway spruce. The largest aphids are mature apterous virginoparae; an oviparous female showing the white pericaudal wax ring is on the left centre of the colony. (C/S 35753) Bottom left: Colonies of Schizolachnus pineti on the needles of Corsican pine transplants showing the densely packed aphids and the wax coating over their body surfaces. (C/S 35752) Bottom right: Eggs of Pine aphid (Cinara pini) on pine needles showing characteristic grouping and colour change from yellow (of new laid egg) through brown to black. (C/S 35751) FORESTRY COMMISSION BULLETIN No. 58 Conifer Lachnids in Britain C. I. Carter and N. R. Maslen Line drawings by N. J. Fielding Forestry Commission Research Station, Alice Holt Lodge, Farnham, Surrey LONDON: HER MAJESTY’S STATIONERY OFFICE © Crown Copyright 1982 First published 1982 ISBN 0 11 710151 6 CONTENTS Page A b stract iv 1. Introduction 1 2. The association of conifer lachnids and the host plant 3 3. Honeydew 7 4. Glossary of terms used in the life cycle of conifer lachnids 10 5. Field key to conifer lachnids commonly occurring in Britain 14 6. Morphological keys 17 7. Accounts of the species in Britain 39 References 70 Acknowledgements 74 Index to aphid names 75 ABSTRACT Field keys and morphological keys with descriptions and illustrations are given for the identifications of the 27 aphids of the family Lachnidae known to occur on conifers in Britain. The strong influence of their host plant upon these insects and the impact some of them have on the growth of forest trees and amenity plantations throughout the world is discussed. The importance of conifer aphid honeydew from various species in the production of forest honey is reviewed. Accounts of each species include recent synonymy, descriptions of morphs, type of life cycle, host plants, distribution and economic importance. SOMMAIRE L’article comporte des tableaux d’observation sur le terrain et morphologiques accompagnds de descriptions et d’illustrations permettant l’identification des 27 pucerons de la famille Lachnidae qui sont trouvds sur les coniffcres en Grande Bretagne. L’influence considerable exercde par l’amphitryon sur ces insectes et l’effect de certains d’entre eux sur la croissance des arbes forestiers et des plantations d’agrdment dans le monde entier sont traitds. L’importance de la miellde de diverses espdces de pucerons des conif£res pour la production du miel de forSt est considdrde. Les profils de chaque espdce comprennent la synonymie rdcente, descriptions des formes, le genre de cycle vital, les amphitryons, la distribution et l’importance pour l’dconomie. UBERSICHT Zur Bestimmung der 27 Arten von Blattlausen der Lachnidae Familie, die auf GroBbritanniens Koniferen vorkommen, werden Feldbeobachtungs— und morphologische Klassifikationstabellen, sowie Beschreibungen und Illus- trationen, angefiihrt. Es wird der starke EinfluB behandelt, den die Wirtspflanze auf diese Insekten ausiibt, sowie andererseits deren groBe Wirkung auf das Wachstum der Baume und der Parkanlagen der ganzen Welt. Die Bedeutung des Honigtaus der verschiedenen Arten von Koniferenblatt- lausen bei der Herstellung von Waldhonig wird betrachtet. Die Berichte iiber die einzelnen Arten enthalten die neueste Zusammenstellung wissenschaftlicher Namen, Beschreibungen der Formen, Typen des Lebenszyklus, Wirtspflanzen, Ausbreitung und wirtschaftliche Bedeutung. 1. INTRODUCTION This bulletin brings together recent information on Until recently not much special attention has been the various species of conifer-feeding aphids belong­ given to the lachnids in Britain. The increase in ing to the family L achnidae that are known to occur numbers of species recorded now in 1980 over those in Britain. The specimens studied have been mainly listed in A Check List of British Insects (Kloet and derived from collections made in Britain over the Hinks, 1945) illustrates the point. This lack of past 15 years from plantations and arboreta or those attention contrasts with a traditional interest in the accompanying forest and nursery enquiries sent to group in other parts of Europe where the potential the Forestry Commission. Keys are given for the of lachnids to damage growing conifers has long identification of both living aphids and prepared been recognised as has their value as producers of specimens. Individual accounts for each species highest quality honeydew, the raw material for include descriptions of the feeding sites, host plants, forest honey. The reputation of honeydew amongst life history, economic importance and distribution. British beekeepers in this last respect is curiously at The family L achnidae is a distinct part of the variance with that of their European counterpart, super-family Aphidoidea and can be readily recog­ and it is quite certain that whilst the former has nised by certain morphological features. The life based his opinion on an inbuilt suspicion of the cycle of lachnids is completed on a single host plant untried, the latter has relied on centuries of and does not therefore have the woody plant/her­ experience. baceous plant alternation pattern so familiar in A recent taxonomic review of the genus Cinara by many agricultural aphid species. Some lachnid Dr V. F. Eastop has been a basis upon which the species attain a very large size for the super-family. present biological work has developed. Duplicates They may also possess very long mouthparts with of the many species encountered have been depo­ which to pierce the bark of trees and reach the sappy sited with him at British Museum (Natural History). tissues containing their liquid food. Similarly, access to the Rothamsted Insect Survey All conifer lachnids have a very limited host material kindly allowed us by Dr L. R. Taylor has range, nearly always confined to one plant genus provided opportunity for the building of a more and often restricted to a few species. Of the many comprehensive picture of the distribution and conifers now grown in Britain only two of the three dispersal behaviour of each species. native species (Pinus sylvestris and Juniperus com­ m unis) are host plants. jrAntennal Segments ii a •Muscle Attatchment Plates --Siphuncular Femur- - Cone 'Siphunculus Cauda Tibia Tarsus I Tarsus II- Figure 1. General morphological features of an apterous viviparous female ofCinara piceae. 2 2. THE ASSOCIATION OF CONIFER LACHNIDS AND THE HOST PLANT Feeding sites and damage young Douglas fir so their growth was only 'A to 'k that of uninfested ones. Keen (1938) reported that several species of lach­ nids cause considerable injury to conifers in North Effect of foliage feeding species America. The visible signs of this injury are usually a yellowing of foliage or a reduction of growth Species of the genera E ulachnus and Schizolachnus especially of young trees (Furniss & Carolin, 1977). feed and make colonies on the needles; whereas Where a particular species of lachnid feeds, at any those in the genus Cinara choose other parts of the one time of the year, is often restricted and does not tree although some species do feed in close vary much from tree to tree (Bradley 1959). There proximity to needles or on new shoot axes that are is, however, a tendency for some species to green and unlignified. The probing behaviour of gradually move as a colony to other feeding sites on Eulachnus agilis on pine foliage, described by Bliss the same plant during the year. This may be done to et al (1973), caused chlorosis and premature drop­ exploit new food sources which become available as ping of needles. Although there are no obvious the season progresses or to acquire some protection. morphological changes in the plant, it is thought that Aphids have to insert their piercing mouth-parts the salivary secretion may have physiological effects through various layers of plant tissue to reach cells such as increasing respiration and decreasing photo­ rich in nutrients. Lachnids are the giants among the synthesis. Both Schizolachnus pineti in Britain and aphids and many species are equipped with excep­ S. piniradiatae in North America live in small dense tionally long piercing mouth-parts to exploit the colonies on pine needles causing the attacked food source beneath the bark of stems and branches needles to senesce prematurely. Under heavy of mature trees. As the long mouth-parts are forced attacks, a large proportion of a tree’s photosynthetic into the plant, enzymes are injected with saliva to area can be lost. Thompson (1977) found high assist penetration between plant cells. Sometimes at densities of S. pineti associated with a marked these sites, where sap-feeding Hemipterous insects reduction in growth of young pines. feed, odd tissue deformities or characteristic galls develop. Effect of shoot and twig feeding Periodic attacks from Cinara cupressi have occurred Effect of stem feeding species on growth over a number of years in Europe. Its presence is not always easily detected, but hidden colonies on The growth reactions of plants to local auxin Cupressus spp. can sometimes be located by exten­ applications are not unlike galled tissue caused by sive sooty mould fungi on the lower foliage (Fox insects. This analogy led Nuorteva (1956) to look for Wilson, 1948). Bad attacks can also occur on certain the presence of plant-growth substances in the saliva Thuja and Juniperus species as well. Gunkel (1963) of certain Hemipterous insects. Amongst the insects described the symptoms of reddening of needles and tested in the bioassay was the colonial stem-feeding twig death, which can often lead to whole plants Cinara piceae. Though this aphid does not produce dying. Luisi and Triggiana (1977) report a wide­ anything in the form of a gall, Nuorteva’s investiga­ spread occurrence of aphid damge to Cupressus in tion showed that high concentrations of salivary recent years in Central and Southern Italy.