No abstract

Bradysia odoriphaga is an agricultural pest in China’s vegetable industry. In this study, pupae and adults were exposed to various non-lethal high-temperatures. The results demonstrated a decreased rate of eclosion once the pupae were exposed to temperatures exceeding 37 °C for 1 h. No effect on the lifespan of unmated female adults was observed after exposure to temperature stress, while unmated male adult lifespan decreased (>37 °C for 2 h). The size of the testis and ovaries for unmated male and female adults decreased, as did the fecundity and egg hatching rate for mated females. Compared with the control group (25 °C), the testis size of unmated male adults decreased after high-temperature stress followed by recovery at 25 °C for 1 h, though the size of the ovaries of female adults did not change. Additionally, the size of the testis and ovaries for unmated male and female adults decreased following high-temperature stress and 24 h of recovery at 25 °C. High temperatures affected males more than females; 37 °C is the critical temperature to control the population of B. odoriphaga. These results lay the foundation for the future development of environmentally friendly high-temperature prevention and pest-control strategies.

The soil inhabits many microbes, including plant parasitic nematodes. Plant parasitic nematodes are reported to cause substantial damage to crops which results in yield and economic losses. Chemical control is the most widely used method to control plant parasitic nematodes. However, the consequences of synthetic chemicals are detrimental to human health, animals, and the environment and face so many strict regulatory measures. Synthetic chemicals are also not reliable with their inability to provide long-term protection. Many studies have shown that the use of beneficial fungi and bacteria has the potential to prevent and suppress plant parasitic nematodes while keeping the environment safe. Several experiments have demonstrated that bioproducts of microbial origin are cheap, safe, and provide long-lasting biocontrol effects against pathogens both in vitro and field conditions. Therefore, this review aims to discuss mechanisms that beneficial microbes and their products use to successfully suppress plant parasitic nematodes. The review also explains the importance of using commercial bionematicides in the sustainable management of plant parasitic nematodes. The existing challenges that are limiting the full application of beneficial microbes, and what needs to be done to fully utilize biocontrol agents in the management of plant parasitic nematodes have also been discussed. To the best of our knowledge, this review has come at the right time to give researchers and plant growers more options when several synthetic chemical nematicides are being banned by regulatory authorities due to their hazardous effects.

Akebia trifoliata (Thunb.) Koidz. is a species in the family Lardizabalaceae, which belongs to deciduous woody lianas. It is an important species of plant used in Chinese medicine. In July 2019, a leaf spot disease was observed on A. trifoliata in a nursery garden in Jingzhou (N 30° 21', E 112° 19'), Hubei Province, China. Symptoms initially appeared as small brown spots and subsequently developed into subcircular or irregular-shaped brown necrotic lesions. In severe cases, the leaves became completely necrotic and abscised. The incidence of leaf symptoms on affected plants ranged was between 30% and 40%. To isolate the pathogen, pieces of symptomatic leaves were collected and excised at the margins of lesions, surface disinfected with 70% ethanol and 0.1% HgCl2, rinsed three times with sterile water, placed on potato dextrose agar (PDA) amended with 50 μg/ml kanamycin, and incubated at 28°C in the dark for 3 days. Isolated colonies were subcultured by transferring hyphal tips. Six fungal isolates were isolated from the collected tissues. All six isolates had similar colony morphologies on on PDA and were composed of white flocculent aerial hyphae. The average radial growth rate of colonies after 7 days was 11.2 mm/d. Isolates were later cultured on 20% V8 juice agar for 20 days to encourage sporulation. Sporangia were produced on V8 media and were colorless, inverted, pear-shaped, and terminal, with obvious mastoid, 22 to 34 × 28 to 46µm (n=50); Oospores were light brown, and suborbicular, with thick wall, 18 to 26µm (n=20); Globose chlamydospores were light brown, and suborbicular, 12 to 32µm (n=50). Antheridia were not observed suggesting homothallism. These morphological charactertistics were identical to those reported for Phytophthora nicotianae (Erwin and Ribeiro 1996). We selected a single isolate ‘B2’, for molecular identification because it was the most aggressive in leaf pathogenicity assays. The internal transcribed spacer (ITS) region of rDNA was amplified and sequenced using primers ITS1/ITS4 (White et al. 1990). BLAST analyis revealed that the ITS sequence (GenBank accession nos. MT472132) was 100% identical to other P. nicotianae strains (GenBank accession nos. KJ754387). To fulfill Koch’s postulates, a 50 ml zoospores suspension (106 spores/ml) of B2 was sprayed on the foliage of three 1-year-old healthy seedlings. Sterile distilled water to inoculate control plants. After 10 days, typical symptoms of dark brown spots were observed on all the inoculated leaves, while the control leaves remained asymptomatic. P. nicotianae was re-isolated from the inoculated, symptomatic leaves, thus confirming Koch's hypothesis. The experiment was repeated three times. To the best of our knowledge, this is the first report of P. nicotianae causing leaf spot on A. trifoliata in China. P. nicotianae is a common stramenopile pathogen that infects many plant hosts. The presence of this pathogen in an A. trifoliata nursery should be carefully considered to mitigate possible outbreaks of this disease in other fields in this growing region.