Sentinel trees: a new method for early warning
The early detection of insect invaders is a challenge in plant health, as many of these insect species were not necessarily known to cause significant damage in their native range and some were not even known to science before being introduced into a new area. As Asia is currently considered to be the main origin of insect invaders to Europe, sentinel trees were planted in China during 2007-2011 as an early warning tool to evaluate the potential of Asian insects to colonize European trees. Seedlings (1-1.5 m tall) of 5 broadleaved (Carpinus betulus, Fagus sylvatica, Quercus petraea, Q. suber, Q. ilex) and 2 conifer species (Abies alba, Cupressus sempervirens) were planted in blocks of 100 seedlings at two widely separated sites: in a nursery in Beijing and in a forest environment near Fuyang (Anhui province). Sentinel trees were regularly inspected for the presence of insects (every month from May to October from 2007 to 2011 in Beijing – every 2 weeks from May to October from 2008 to 2011 in Fuyang). As a result, 104 insect species, mostly defoliators, were observed at various stages (eggs, larvae, pupae, adults) on European trees. Although many insects were probably incidental feeders, 38 species colonized the European sentinel trees more than 5 times during the studied period. The full list is included in the original paper, but a list of insects which could be identified to the species level has been extracted below by the EPPO Secretariat (in order of occurrence).
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Species
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Order: Family
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Known host in China
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European trees in China
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Compsapoderus continentalis
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Coleoptera: Attelabidae
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?
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C. betulus, F. sylvatica, Q. petraea, Q. suber
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Altica cirsicola
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Coleoptera: Chrysomelidae
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Thistles
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C. sempervirens, Q. suber
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Holotrichia diomphalia
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Coleoptera: Scarabeidae
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Field crops, Azadirachta, Prosopis, Ziziphus, Populus
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A. alba, C. betulus, C. sempervirens, F. sylvatica, Q. ilex, Q. petraea, Q. suber
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Holotrichia trichophora
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Coleoptera: Scarabeidae
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Field crops, Sapium, Cinnamomum, Castanea
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A. alba, C. betulus, C. sempervirens, F. sylvatica, Q. ilex, Q. petraea, Q. suber
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Rhopalus sapporensis
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Hemiptera: Coreidae
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Rice, field crops
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Q. ilex, Q. petraea
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Pteroma nr pendula
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Lepidoptera: Psychidae
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Legume trees
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C. betulus, F. sylvatica, Q. ilex, Q. petraea, Q. suber
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Lema coronata
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Coleoptera: Chrysomelidae
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Commelina communis
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Q. petraea
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Lema diversa
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Coleoptera: Chrysomelidae
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Commelina communis
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Q. petraea
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Calomycterus obconicus
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Coleoptera: Curculionidae
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Field crops, polyphagous
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Q. suber
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Echinocnemus squameus
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Coleoptera: Curculionidae
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Field crops, rice
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Q. petraea
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Basilepta fulvipes
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Coleoptera: Eumolpidae
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Cerasus, Prunus, Malus, Pterocarya
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Q. petraea
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Anomala corpulenta
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Coleoptera: Rutelidae
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Field crops, fruit trees, Populus
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Q. petraea
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Mimela chinensis
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Coleoptera: Rutelidae
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Field crops, fruit trees
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C. betulus, Q. petraea
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Holotrichia parallela
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Coleoptera: Scarabeidae
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Ulmus, Populus, Salix, field crops
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A. alba, C. betulus, C. sempervirens, F. sylvatica, Q. ilex, Q. petraea, Q. suber
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Holotrichia titanus
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Coleoptera: Scarabeidae
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Field crops
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A. alba, C. betulus, C. sempervirens, F. sylvatica, Q. ilex, Q. petraea, Q. suber
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Cletus tenuis
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Hemiptera: Coreidae
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Field crops, rice, wheat, maize
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C. betulus
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Dolycoris baccarum
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Hemiptera: Pentatomidae
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Field crops, fruit trees
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C. betulus
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Eysarcoris guttiger
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Hemiptera: Pentatomidae
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Field crops
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C. betulus, Q. petraea
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Trabala vishnou
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Lepidoptera: Lasiocampidae
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Juglans, Castanea, Quercus, Malus
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Q. petraea, Q. suber
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Cifuna nr locuples
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Lepidoptera: Lymantridae
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Field crops, Lythrum salicaria
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Q. petraea, Q. suber
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Acronicta rumicis
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Lepidoptera: Noctuidae
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Pyrus, Malus, Amygdalus, Rumex, Polygonum
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Q. petraea
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The use of sentinel plants to identify possible insect threats is promising but several constraints were encountered during this project: the taxonomic identification was difficult as a large proportion of the collected specimens were larvae, the duration of the experiment was too short to monitor bark and wood borers or fruit/cone pests which develop on larger trees, climatic and environmental factors have seriously affected the acclimatization and survival of tree seedlings, logistical and administrative difficulties were major constraints when planting trees in a foreign country. The use of an alternative method based on arboretum surveys, relying on a worldwide network of arboreta, botanical gardens and nurseries is also discussed. This latter approach tends to overcome the logistical and administrative difficulties, and allows studies on mature trees. However, it usually relies on a limited number of trees of the same species. In conclusion, both approaches were considered useful and complementary to identify potential insect invasions and achieve early warning.
Sources
Roques A, Fan JT, Courtial B, Zhang YZ, Yart A, Auger-Rozenberg MA, Denux O, Kenis M, Baker R, Sun JH (2015) Planting sentinel European trees in Eastern Asia as a novel method to identify potential insect pest invaders. PlosOne DOI: 10.1371/journal.pone.0120864 http://www.plosone.org/article/fetchObject.action?uri=info