Field Assessment of the Host Range of Aculus mosoniensis (Acari: Eriophyidae), a Biological Control Agent of the Tree of Heaven (Ailanthus altissima)

Tree of heaven (Ailanthus altissima) is a fast-growing deciduous tree native to China, considered a serious invasive species worldwide, with several socio-economic and ecological impacts attributed to it. Chemical and mechanical methods have limited efficacy in its management, and biological controls may offer a suitable and sustainable option. Aculus mosoniensis (Ripka) is an eriophyid mite that has been recorded to attack tree of heaven in 13 European countries. This study aims to explore the host range of this mite by exposing 13 plant species, selected either for their phylogenetic and ecological similarity to the target weed or their economic importance. Shortly after inoculation with the mite, we recorded a quick decrease in mite number on all nontarget species and no sign of mite reproduction. Whereas, after just one month, the population of mites on tree of heaven numbered in the thousands, irrespective of the starting population, and included both adults and juveniles. Significantly, we observed evidence of damage due to the mite only on target plants. Due to the specificity, strong impact on the target, and the ability to increase its population to high levels in a relatively short amount of time, we find A. mosoniensis to be a very promising candidate for the biological control of tree of heaven

The importance of cryptic species and subspecific populations in classic biological control of weeds: a North American perspective

Classical biological control of weeds depends on finding agents that are highly host-specific. This requires not only correctly understanding the identity of the target plant, sometimes to subspecific levels, in order to find suitable agents, but also identifying agents that are sufficiently specific to be safe and effective. Behavioral experiments and molecular genetic tools have revealed that some arthropod species previously thought to be polyphagous really consist of multiple cryptic species, host races or biotypes, some of which are more host-specific than others. Whereas true species are reproductively isolated, individuals from subspecific populations may potentially interbreed with those of other populations if they should encounter them. Furthermore, biotypes may consist of individuals sharing a genotype that is not fixed within a monophyletic group, and thus may not be evolutionarily stable. This raises the question of how such populations should be classified, and how to confirm the identity of live arthropods before releasing them as classical biological control agents. The existence of host races or cryptic species may greatly increase the number of prospective biological control agents available. However, it may also create new challenges for governmental regulation. These issues are discussed using pertinent examples, mainly from North America

Resistance of grapevine to the erineum strain of Colomerus vitis (Acari: Eriophyidae) in western Iran and its correlation with plant features.

Trisetacus juniperinus (Nalepa) sensu Keifer (Acari: Eriophyoidea: Phytoptidae) causes irregular development of buds, shoot deformations and stunted growth of trees, resulting in a serious threat to nurseries and young stands of Cupressus sempervirens L. (Mediterranean cypress). Recently, some cypress clones selected for their resistance to the fungal canker agent Seiridium cardinale (Wag.) have shown high susceptibility to the mite. Considering its tiny body, its hidden lifestyle inside the buds and the probable occurrence of other species (the vagrant Epitrimerus cupressi (Keifer) is common on the Mediterranean cypress in Italy), detection and monitoring of T. juniperinus require taxonomic expertise and are often time-consuming and challenging before serious damage is discernible. In the present study, a rapid, cost-effective PCR-based method was developed and validated to detect T. juniperinus on cypresses. The cytochrome c oxidase subunit I gene was amplified with degenerate and specific primers, but the latter were the only ones able to discriminate between T. juniperinus and E. cupressi. PCR products distinguished the two species both in a pool of individuals in a mixed population of both species and in single individuals, indicating the sensitivity of the detection method. PCR–RFLP (restriction fragment length polymorphism) by means of XmnI and XbaI endonucleases separated the two species. Furthermore, a washing-sieving protocol was used to make mite collection from the tree sample faster and simpler; this procedure did not interfere with the molecular detection of the species. The possibility of the routine use of this assay to monitor quarantine eriophyoids infesting plant material is discussed

Study of defense-related gene expression in grapevine infested by Colomerus vitis (Acari: Eriophyidae)

Real-time quantitative polymerase chain reaction was used to study the expression of some marker genes involved in the interaction between grape (Vitis vinifera L.) and the erineum mite Colomerus vitis Pagenstecher (Acari: Eriophyidae). Potted vines of cultivars Atabaki (resistant to C. vitis), Ghalati (susceptible to C. vitis) and Muscat Gordo (moderately resistant to C. vitis) were infested at the six-leaf stage. The expression of protease inhibitor (PIN), beta-1,3-glucanase (GLU), polygalacturonase inhibitor (PGIP), Vitis vinifera proline-rich protein 1 (PRP1), stilbene synthase (STS), and lipoxygenase (LOX) genes was assessed on young leaves collected 96, 120 and 144 h after mite infestation (hami). As a control, non-infested leaves collected 24 h before mite infestations were used. Differences were detected in expression of the selected genes during the C. vitis–grapevine interaction. The resistant cultivar Atabaki increased the expression of LOX, STS, GLU, PGIP and PRP1 genes during the first 120 hami. On the contrary, in the susceptible Ghalati, all selected genes showed an expression level similar or lower than non-infested leaves. Muscat Gordo increased the expression of all selected genes in comparison with non-infested leaves, but it was lower than in Atabaki. Significant transcript accumulation of PIN gene was detected for Muscat Gordo whereas it was slightly up-regulated in Ghalati and Atabaki. LOX, STS, PIN, GLU, PGIP and PRP1 genes were clearly expressed in response to C. vitis infestation. We therefore infer that expression of PGIP, PIN and PRP1 genes could represent a defense strategy against C. vitis infestations in grapevine leaves