Defence Responses Associated with Elicitor-Induced, Cultivar-Associated Resistance to Latania Scale in Kiwifruit

Latania scale insect is a pest of global significance affecting kiwifruit. The sessile insect (life stage: settled crawler—mature adult) is covered with a waxy cap that protects it from topical pesticides, so increasingly, a selection of resistant cultivars and application of elicitors are being used in pest control. Thus far, the application of a salicylic acid (SA) phytohormone pathway elicitor, acibenzolar-S-methyl (ASM), has been shown to reduce insect development (as indicated by cap size) on one kiwifruit cultivar (‘Hayward’). To investigate how cultivar-associated resistance is affected by the ability to respond to different elicitors, we measured phytohormones (by LCMS) and gene expression (by qPCR and NanoString) on latania scale-tolerant ‘Hort16A’ and susceptible ‘Hayward’ kiwifruit over two seasons. Potted plants in the presence/absence of settled latania scales were treated with ASM (0.2 g/L) or methyl jasmonate (MeJA, 0.05% v/v), representing elicitors of the SA and JA signalling pathways, respectively. ‘Hort16A’ cultivar resistance to latania scale was associated with elevated expression of SA and SA-related defence genes (PR1 and two PR2 family genes) in the ASM treatment. MeJA treatments did not significantly affect insect development in ‘Hayward’ (latania scale did not survive on ‘Hort16A’) and did not correlate with phytohormone and gene expression measurements in either cultivar. ‘Hayward’ had greater concentrations than ‘Hort16A’ of inert storage forms of both SA and JA across all treatments. This information contributes to the selection of tolerant cultivars and the effective use of elicitors for control of latania scale in kiwifruit.

VIRULENCE OF ENTOMOPATHOGENIC NEMATODES TO THREE SOFT SCALE INSECT SPECIES

Virulence of commercial strains of entomopathogenic nematode (EPN) Steinernema carpocapsae (Weiser), Steinernema feltiae Filipjev and Heterorhabditis bacteriophora Poinar (Rhabditida: Steinernematidae, Heterorhabditidae), were tested on young females of Pulvinaria hydrangeae Steinweden, Partenolecanium corni (Bouché) and Coccus pseudomagnoliarum (Kuwana) (Hemiptera, Coccidae) and a native strain of H. bacteriophora was tested on citricola scale, C. pseudomagnoliarum. The laboratory tests were carried out in small plastic Petri dishes with infective juveniles (IJ) applied on filter paper covering the bottom. Results showed that all EPN tested were virulent to all three soft scale insect species. Recorded mortality of insects at the highest concentration of approximately 50 IJ per cm2 exceeded 64% in all combinations of nematode and scale species tested. Within the same nematode concentration, scales’ mortality of 90% and above was recorded for P. corni with all nematode species, P. hydrangeae with S. carpocapsae (Nemastar) and C. pseudomagnoliarum with native H. bacteriophora strain. All scale species were good hosts for all nematode species. This is the first report of EPNs to parasitize soft scale insects and one of the few among Coccoidea. The level of parasitism recorded is promising for potential use in management of scale insects.

Comparative Study on Pseudaulacaspis Pentagona Resistance of Four Different Cultivars of Kiwifruit

Background:Kiwifruit is a common and popular fruit around the world. However, white peach scale (Pseudaulacaspis pentagona) [Targioni-Tozzetti], a scale insect with a wide range of hosts, seriously affects the yield and quality of kiwifruit. To investigate the differences in resistance of different kiwifruit cultivars to Pseudaulacaspis pentagona, cellular structure and gene expression assays were used to explain the mechanism. Results:In this study, based on the stability of the rate of injury fruit, we selected four cultivars from fifty kiwifruits for in-depth study, including “LC-04285”, “CF-3”, “DA-7B” and “Hayward”. By analyzing the differences in the anatomical structure of the canes of these cultivars, we found that the resistant cultivar "LC-04285" had thicker cuticle, denser epidermis and cortex. The real-time quantitative PCR data indicated that the expression levels of genes related to cuticle synthesis and formation of epidermis and cortex are also higher in “LC-04285”. Jasmonic acid (JA) is an important hormone involved in plant defense against many insect pests. In this study, we found that the expression levels of JA receptor COI1 were higher in “LC-04285”. However, the expression levels of AcJAZs, which played negative role in JA signaling, were higher in susceptible cultivar “Hayward”. Besides, the expression levels of AcICS, AcPAL4, AcPAL5, and AcNPRs, which were involved in salicylic acid (SA) synthesis and SA response, were also higher in “LC-04285”. Conclusions:Our results revealed the mechanism of kiwifruit resistance to P. pentagona at the molecular and cellular levels. This study provided useful guidance for breeding insect-resistant kiwifruit in future.

A checklist of the scale insects (Hemiptera: Coccomorpha) of Kenya, with some new combinations

The checklist of scale insect species recorded from Kenya comprises 14 families, 128 genera and 304 species, of which 207 (68.0%) are probably of African origin, 91 (29.9%) have been introduced from outside Africa and six (2.0%) are of unknown origin. Out of the 207 African species, only 11 (5.3%) have been recorded damaging plants, whereas out of the 91 introduced species, 45 (49.5%) have caused or are highly likely to cause plant damage in Kenya. The most economically important scale insect families in Kenya are (in order of importance) the Pseudococcidae, Coccidae and Diaspididae. Four new combinations are made: Eurycoccus glomerulus De Lotto is transferred to Trionymus, as Trionymus glomerulus (De Lotto) comb. n.; Trionymus sativus James is transferred to Paracoccus, as Paracoccus sativus (James) comb. n.; Pseudococcus masakensis James is transferred to Nipaecoccus as Nipaecoccus masakensis (James) comb. n., and Spilococcus commiphorae De Lotto is transferred to Paracoccus, as Paracoccus commiphorae (De Lotto) comb. n.

Study of The Effect of Hot Water Extract of Garlic and Pepper Plants, With Different Concentrations Saline Solution on The Mortalityon Parlatoria Blanchardi (Targioni-Tozzetti) on Date Palms

The scale insect Parlatoria blanchardi (Homoptera : Diaspdidae) is one of the important pests, that cause damage to all parts of the date palm in the central and southern governorates of Iraq, In order to reduce the negative effects of pesticides on the environment. Two types of hot water extracts, of Capsicum annuam and Alliu sativum, were used in the field at three concentrations of 5, 10 and 15 g/liter of water, in addition to the use of the saline solution in three concentrations of 15, 20 and 25 g/liter of water, to reduce the population density of P. blanchardi. The results showed that the plant extracts and the saline solution, had high efficiency in reducing the population density of P. blanchardi after one week of spraying, as the saline solution registered the best mortality of 100% at the three concentrations used and with a significant difference from A. sativum extract, which recorded the highest mortality of 80% for the insect at the concentration of 15 g/L and the lowest mortality was 56% over the concentration of 10 g/L, while the C. annuam extract recorded the highest mortality of 80% at a concentration of 15 g/L, and the lowest mortality at a concentration of 5 g/L was 55%.

Transmission of Grapevine leafroll-associated virus-1 (Ampelovirus) and Grapevine virus A (Vitivirus) by the Cottony Grape Scale, Pulvinaria vitis (Hemiptera: Coccidae)

The cottony grape scale Pulvinaria vitis is a scale insect colonizing grapevine; however, its capacity as a vector of grapevine viruses is poorly known in comparison to other scale species that are vectors of viral species in the genera Ampelovirus and Vitivirus. The ability of P. vitis to transmit the ampeloviruses Grapevine leafroll-associated viruses [GLRaV]−1, −3, and −4, and the vitivirus Grapevine virus A (GVA), to healthy vine cuttings was assessed. The scale insects used originated from commercial vine plots located in Alsace, Eastern France. When nymphs sampled from leafroll-infected vineyard plants were transferred onto healthy cuttings, only one event of transmission was obtained. However, when laboratory-reared, non-viruliferous nymphs were allowed to acquire viruses under controlled conditions, both first and second instar nymphs derived from two vineyards were able to transmit GLRaV−1 and GVA. This is the first report of GLRaV−1 and GVA transmission from grapevine to grapevine by this species.

Towards the identification of the scale insects (Hemiptera: Coccomorpha) of continental Africa: 1. Identification of the families

Scale insects (Hemiptera: Sternorrhyncha: Coccomorpha) are obligate plant parasites feeding on plant sap; some are damaging pests in agriculture, horticulture and forestry. Despite their economic importance, the scale insects found in continental Africa have not been extensively studied and the keys for identifying them are incomplete and scattered through the literature in several languages. The aim of this study is to improve our understanding of the African scale insect fauna. As a first step towards their identification, we provide a key to the 23 families currently known from continental Africa, based on slide-mounted adult females, covering Aclerdidae, Asterolecaniidae, Cerococcidae, Coccidae, Conchaspididae, Dactylopiidae, Diaspididae, Eriococcidae, Halimococcidae, Kermesidae, Kerriidae, Kuwaniidae, Lecanodiaspididae, Margarodidae, Matsucoccidae, Micrococcidae, Monophlebidae, Ortheziidae, Phoenicococcidae, Pseudococcidae, Putoidae, Rhizoecidae and Stictococcidae.

Host phylogeny and ecological associations best explain Wolbachia host shifts in scale insects

Wolbachia are among the most prevalent and widespread endosymbiotic bacteria on earth. Wolbachia’ s success in infecting an enormous number of arthropod species is attributed to two features: the range of phenotypes they induce in their hosts, and their ability to switch to new host species. Whilst much progress has been made in elucidating the phenotypes induced by Wolbachia, our understanding of Wolbachia host shifting is still very limited: we lack answers to even fundamental questions concerning Wolbachia’s routes of transfer and the importance of factors influencing host shifts. Here, we investigate the diversity and host-shift patterns of Wolbachia in scale insects, a group of arthropods with intimate associations with other insects that make them well-suited to studying host shifts. Using Illumina pooled amplicon sequencing of Wolbachia-infected scale insects and their direct associates we determined the identity of all Wolbachia strains, revealing that 32% of samples were multiply infected (with up to five distinct strains per species). We then fitted a Generalised Additive Mixed Model (GAMM) to our data to estimate the influence of factors such as the host phylogeny and the geographic distribution of each species on Wolbachia strain sharing among scale insect species. The model predicts no significant contribution of host geography but strong effects of host phylogeny, with high rates of Wolbachia sharing among closely related species and a sudden drop-off in sharing with increasing phylogenetic distance. We also detected the same Wolbachia strain in scale insects and several intimately associated species (ants, wasps, beetles, and flies). This indicates putative host shifts and potential routes of transfers via these associates and highlights the importance of ecological connectivity in Wolbachia host-shifting.

Occurrence and spread of Ceroplastes cirripediformis Comstock (Hemiptera: Coccomorpha: Coccidae) in India

The notoriously destructive and invasive soft scale, Ceroplastes cirripediformis Comstock (Hemiptera: Coccomorpha: Coccidae), is recorded for the first time from India. The scale is redescribed to facilitate its identification and information on its host range, natural enemies and distribution is provided. An identification key to the Indian species in this genus is given. Management options in the event of an outbreak are discussed briefly. The establishment of this scale insect warrants special attention in India as it is a potentially damaging plant pest and has a broad host range across many plant families.