Research Progress on the Dendrolimus spp. Pheromone: From Identification to Molecular Recognition

Pest categorisation of Dendrolimus punctatus

The EFSA Panel on Plant Health performed a pest categorisation of Dendrolimus punctatus (Lepidoptera: Lasiocampidae), following a commodity risk assessment of bonsai Pinus parviflora grafted onto P. thunbergii from China, in which D. punctatus was identified as a pest of possible concern to the European Union (EU). D. punctatus, also known as the Masson pine caterpillar, is present in China, Taiwan, Vietnam, India and has recently spread to Japanese islands close to Taiwan. Larval feeding on the needles of Pinus elliottii, P. luchuensis, P. massoniana, P. merkusii and P. tabulaeformis causes important damage. D. punctatus larvae can also feed on P. armandii, P. echinata, P. latteri, P. parviflora, P. sylvestris var. mongolica, P. taeda, P. taiwanensis and P. thunbergii, but full development on these hosts is uncertain. The pest has three to five generations per year; winter is spent as larvae on branch tips, on tree trunks and in the soil. The females lay egg clusters on pine needles. Pupation occurs in cocoons attached to branches or needles. D. punctatus could enter the EU either as eggs, larvae or pupae in the foliage of plants for planting or cut branches, as larvae on wood with bark or as overwintering larvae in branches, crevices in the bark or in the litter of potted plants. However, Annex VI of 2019/2072 prohibits the introduction of D. punctatus hosts (Pinus spp.) from countries and areas where the pest occurs. There are climate zones where the pest occurs in Asia that also occur in the EU, though they are limited, which constitutes an uncertainty regarding establishment. The pest's main hosts are not grown in the EU. However, the fact that it attacks the North American Pinus echinata, P. elliottii and P. taeda in its Asian native area suggests a potential capacity to shift to pine species occurring in the EU territory. D. punctatus satisfies all the criteria that are within the remit of EFSA to assess for it to be regarded as a potential Union quarantine pest. Whether the Pinus commonly found in Europe could act as hosts is unknown but is fundamental, affecting the criteria of establishment and magnitude of impact.

Pathogenicity virulence of Beauveria spp. and biosafety of the BbMQ strain on adult ectoparasitic beetles, Dastarcus helophoroides Fairmaire (Coleoptera: Colydiidae)

Introduction

Beauveria spp. and Dastarcus helophoroides Fairmaire adults were simultaneously released to attack elder larvae or pupae of Monochamus alternatus in pine forests in China. However, little is known about the pathogenicity virulence and biosafety of Beauveria spp. on beneficial adults of D. helophoroides, and specific Beauveria bassiana (Bb) strains should be selected for synthetic release together with D. helophoroides.

Methods

A total of 17 strains of Beauveria spp. were collected, isolated, and purified, and then their mortality, cadaver rate, LT50, spore production, spore germination rate, and growth rate of D. helophoroide adults were calculated based on 0-20 days data after spore suspension and powder contact.

Results and discussion

The lethality rate of BbMQ, BbFD, and BbMH-03 strains to D. helophoroides exceeded 50%, and the cadaver rate reached 70.6%, among which the mortality rate (82.22%), cadaver rate (47.78%), spore production (1.32 × 10⁹ spores/ml), spore germination rate (94.71%), colony dimension (49.15 mm²), and LT₅₀ (10.62 d) of the BbMQ strain were significantly higher than those of other strains (P < 0.01), and the mortality of D. helophoroides adults increased significantly with increased spore suspension concentration, with the highest mortality reaching 92.22%. This strain was identified as Beauveria bassiana by morphological and molecular methods, while the BbWYS strain had a minimum lethality of only 5.56%, which was safer compared to other strains of adult D. helophoroide. Consequently, the biological characteristics and pathogenicity of different Beauveria bassiana strains varied significantly in their effects on D. helophoroide adults, and the safety of different strains should be assessed when they are released or sprayed to control multiple pests in the forest. The BbMQ strain should not be simultaneously sprayed with releasing D. helophoroide adults in the same forest, while the BbWYS strain can be used in concert with D. helophoroide to synergize their effect.