New and emerging insect pest and disease threats to forest plantations in Vietnam

The planted forest area in Vietnam increased from 3.0 to 4.4 million hectares in the period 2010–2020, but the loss of productivity from pests and diseases continues to be a problem. During this period, frequent and systematic plantation forest health surveys were conducted on 12 native and 4 exotic genera of trees as well as bamboo across eight forest geographic regions of Vietnam. Damage caused by insects and pathogens was quantified in the field and laboratory in Hanoi. The threats of greatest concern were from folivores (Antheraea frithi, Arthroschista hilaralis, Atteva fabriciella, Hieroglyphus tonkinensis, Lycaria westermanni,Krananda semihyalina, and Moduza procris), wood borers (Batocera lineolata, Euwallacea fornicatus, Tapinolachnus lacordairei, Xyleborus perforans, and Xystrocera festiva), sap-sucking insects (Aulacaspis tubercularis and Helopeltis theivora) and pathogens (Ceratocystis manginecans, Fusarium solani, and Phytophthora acaciivora). The number of new and emerging pests and pathogens increased over time from 2 in 2011 to 17 in 2020, as the damage became more widespread. To manage these pests and diseases, it is necessary to further invest in the selection and breeding of resistant genotypes, improve nursery hygiene and silvicultural operations, and adopt integrated pest management schemes. Consideration should be given to developing forest health monitoring protocols for forest reserves and other special-purpose forests

Synthesis, characterisation and thermoelectric properties of the oxytelluride Bi2O2Te

Bi2O2Te was synthesised from a stoichiometric mixture of Bi, Bi2O3 and Te by a solid state reaction. Analysis of powder X-ray diffraction data indicates that this material crystallises in the anti-ThCr2Si2 structure type (space group I4/mmm), with lattice parameters a = 3.98025(4) and c = 12.70391(16) Å. The electrical and thermal transport properties of Bi2O2Te were investigated as a function of temperature over the temperature range 300 ≤ T/K ≤ 665. These measurements indicate that Bi2O2Te is an n-type semiconductor, with a band gap of 0.23 eV. The thermal conductivity of Bi2O2Te is remarkably low for a crystalline material, with a value of only 0.91 W m-1 K-1 at room temperature

Daldinia eschscholzii (Ascomycota, Xylariaceae) isolado na Amazônia brasileira: características taxonômicas e condições de crescimento micelial

The Amazon has a high diversity of fungi, including species of the genus Daldinia (Ascomycota, Xylariaceae), which produce secondary metabolites with recognized nematicidal and antimicrobial activity. The ecological role of Daldinia is important, as stromata serve as refuges to many insects and arthropodes, and the fungi contribute to the degradation of vegetable organic matter. The aim of this study was to analyze the taxonomic features and mycelial growth conditions in vitro of a Daldinia specimen collected in the Brazilian Amazon. Morphological and molecular studies of the fungus identified it as D. eschscholtzii. To evaluate mycelial growth, we cultivated the fungus at 20, 25, 30, 35, and 40 °C in malt extract-peptone agar (MEPA), malt extract-peptone (MEP), potato dextrose (PD), and minimum medium (MM). The best mycelial growth occurred at 35 °C, although the greatest amount of biomass was obtained at 25 °C and 30 °C. PD proved to be the best medium for biomass production.A Amazônia apresenta alta diversidade de fungos, incluindo Daldinia (Ascomycota, Xylariaceae), cujas espécies produzem metabólitos secundários com reconhecida atividade antimicrobiana e nematicida. O papel ecológico é importante, visto que estromas servem de abrigo para muitos insetos e artrópodes, além de contribuir na degradação da matéria orgânica vegetal. O objetivo desse estudo foi analizar as características taxonômicas e as condições do crescimento micelial in vitro de um espécime de Daldinia coletado na Amazônia brasileira. Estudos morfológicos e moleculares do fungo o indetificaram como D. eschscholtzii. Para avaliação do crescimento micelial o fungo foi cultivado nas temperaturas de 20, 25, 30, 35 e 40 °C e nos meios de cultura extrato de malte-peptona ágar (EMPA), extrato de malte-peptona (EMP), batata dextrose (BD) e meio mínimo (MM). O melhor crescimento micelial ocorreu a 35 °C, entretanto, a maior quantidade de biomassa foi obtida a 25 e 30 °C. O meio BD provou ser o melhor meio para produção de biomassa

Management of needle-eating caterpillars associated with Pinus massoniana and P. merkusii in Vietnam

Pine tussock moth (Dasychira axutha Collenette (Lymantriidae)) and masson pine caterpillar (Dendrolimus punctatus Walker (Lasiocampidae)) cause serious damage to Pinus massoniana and P. merkusii plantations in Vietnam. An integrated pest management (IPM) program is required to control these pests. Therefore, this study was undertaken to identify damage thresholds and to evaluate control options for implementing IPM in the Northeast and North Central regions of Vietnam. Three damage thresholds were considered: 50% loss of leaf area. Control options were manual collection of eggs and pupae and the use of light traps and biological agents. An initial IPM model was developed for each pest and these gave control efficacies of 82.4% (Da. axutha on P. massoniana) and 77.8% (De. punctatus on P. merkusii). Six extended IPM models were undertaken by forest companies giving pest control efficacies of 79.2%–85.9%. The collection of pine resin provides an important source of income to local communities and the resin yield in the IPM models increased by 20.9%–22.7% compared to untreated control plots. The IPM protocols would help in developing policies that promote a more sustainable management of forest pests in Vietnam, thus reducing dependence on the use of insecticides of environmental and public health concerns

First report of wilt disease in Dalbergia tonkinensis caused by Ceratocystis manginecans

Dalbergia tonkinensis is a rare and valuable rosewood which is being domesticated in home gardens in north Vietnam. Concern for the viability of this new industry has arisen with growers reporting the recent death of trees. This study identified a new wilt disease causing large bole cankers, associated blue staining to the wood, wilted canopies and tree death in home gardens and plantations. From βT1a and βT1b sequence analysis, the Ceratocystis isolates causing wilt disease in D. tonkinensis belong to Ceratocystis manginecans and were shown to be pathogenic with D. tonkinensis seedlings in a nursery trial. They were also able to form stem cankers in Acacia and Eucalyptus. Cankers in 2–11 year-old trees were associated with wounding, primarily from pruning of branches to improve tree form and drilling of trunks in older trees to assess heartwood formation. To mitigate against further damage, it is recommended that pruning be restricted to the dry season and that the practice of drilling trunks be kept to a minimum

Damage caused by Batocera lineolata Chevrolat (Coleoptera: Cerambycidae) in Eucalyptus and its management in Vietnam

The recent emergence of a new cerambycid pest in Eucalyptus plantations in Vietnam is causing concern in the forest sector. This paper confirms the identity of the new pest, assesses the damage caused in the main commercial Eucalyptus clones, and explores preliminary control options for the management of outbreaks. The pest was identified as Batocera lineolata Chevrolat based on mitochondrial cytochrome oxidase 1 analysis. Clonal plantations of E. urophylla × E. grandis (DH32-29) had the most bole damage; E. urophylla × E. pellita (PNCTIV, U6) had low damage; and E. urophylla × E. pellita (PNCT3) and E. urophylla (PN14) were not damaged by B. lineolata. Thirty days after pesticide treatments (fipronil, carbaryl, chlorantraniliprole, chlorpyrifos ethyl mixed with trisiloxane ethoxylate) were applied to the boles of one-year-old DH32-29 trees, damage from B. lineolata was reduced by 73.4 to 77.5%. Applying Bacillus thuringiensis, Beauveria bassiana or Metarhizium anisopliae mixed with Tween 80 were less effective, with damage reduced by 41.3, 31.5 and 30.2%, respectively. It is suggested that clone DH32-29 be replaced with resistant clones PNCT3, PNCTIV or U6 to reduce the risk of wood loss as the pest spreads. Until more effective control strategies can be identified, insecticides provide an option for reducing damage from B. lineolata larvae

Management of Hypsipyla robusta Moore (Pyralidae) damage in Chukrasia tabularis A. Juss (Meliaceae)

Chukrasia tabularis is a high-value tree in the mahogany family and in Vietnam is grown in home gardens and small plantations. One to 3-year old trees are susceptible to shoot tip damage from larvae of Hypsipyla robusta which feed inside the stem. With the recent expansion of C. tabularis plantations, the forestry sector is seeking management options for this pest. Therefore, the efficacy of a range of commercial insecticides and biological agents were evaluated in nursery and plantation experiments. Twenty days after application of carbaryl, carbosulfan, deltamethrin or fipronil to the shoots of 1-year old nursery seedlings, damage from inoculated H. robusta was reduced by 83–100%. Application of Bacillus thuringiensis, Beauveria bassiana or Metarhizium anisopliae were less effective, reducing damage by 58, 33 and 42%, respectively. In 2-year old trees in the field, damage from natural H. robusta infestation was reduced by >75% at 30 days after application of carbaryl, carbosulfan, deltamethrin or fipronil. Including alkyl sulfonate or trisiloxane ethoxylate as adjuvants into the spray mix reduced damage by up to 98%. Soil applied fipronil granules and foliar-applied B. thuringiensis were less effective treatments (72 and 63%, respectively). The most effective treatments can now be evaluated in more extensive trials so that management protocols can be provided to end-users

First report of Tapinolachnus lacordairei (Coleoptera: Cerambycidae) damage in Chukrasia tabularis

Chukrasia tabularis (Meliaceae) has been planted for many decades in home gardens and plantations in Vietnam. Recently, growers have become concerned with attack by stem borers. Tapinolachnus lacordairei J. Thomson 1864 (Coleoptera: Cerambycidae) is identified as a new indigenous pest causing damage to 15 to 30 year-old stands of C. tabularis in Tuyen Quang, Hoa Binh and Thanh Hoa provinces. The leaves of infested trees prematurely senesce or wilt followed by tree death. In 2019, the infestation level was 12.5–22.5% and the damage index was 0.33–0.55. Adults emerge from February to May, mate within 1–3 days and the females lay 20–40 eggs on the bark of healthy and infested trees. The larvae feed first in the phloem and sapwood, and then in the heartwood where they make pupal chambers. Larvae take up to one year to become fully grown. To mitigate against further loss of C. tabularis, cost-effective control strategies need to be developed and steps taken to reduce the risk of dispersal of the pest beyond its native range in SE Asia

Ceratocystis wilt in Chukrasia tabularis in Vietnam: identification, pathogenicity and host tolerance

Chukrasia tabularis is a rare and valuable tree in the mahogany family (Meliaceae) which has been planted with fruit trees in home gardens in Vietnam more than 60 years. Recently, households have become concerned with sporadic trees wilting and dying. In this study we explore this new tree decline. The trunk of diseased trees, with cankers and wilt symptoms, and soil from around roots were sampled and cultures of Ceratocystis were obtained. The causal agent was identified as C. manginecans based on a phylogenetic species hypothesis of β-tubulin. Five C. manginecans isolates from diseased trees and five soil isolates were pathogenic in C. tabularis seedlings in a nursery trial. We used one isolate to explore the tolerance of 59 one-year-old C. tabularis families to inoculation. Of these, 33 families exhibited very strong tolerance (no lesions, no death). This suggests that there are opportunities to employ resistant families in breeding programs and to increase disease tolerance of C. tabularis through genetic gain