Baseline Sensitivity of Echinochloa crus-gall and E. oryzicola to Florpyrauxifen-Benzyl, a New Synthetic Auxin Herbicide, in Korea.

Echinochloa species is one of the most problematic weed species due to its high competitiveness and increasing herbicide resistance. Florpyrauxifen-benzyl, a new auxin herbicide, was recently introduced for Echinochloa management; however, the potential risk for the development of herbicide resistance in Echinochloa species has not been well-investigated. Thus, this study was conducted to evaluate the baseline sensitivity of Echinochloa species to florpyrauxifen-benzyl to estimate the risk of future resistance development. A total of 70 and 71 accessions of Echinochloa crus-galli and Echinochloa oryzicola were collected from paddy fields in Korea, respectively. These two Echinochloa species were grown in plastic pots up to the 5-leaf stage, and treated with florpyrauxifen-benzyl at a range of doses from 2.2 g to 70.0 g a.i. ha-1. Nonlinear regression analyses revealed that GR50 values for E. oryzicola ranged from 4.54 g to 29.66 g a.i. ha-1, giving a baseline sensitivity index (BSI) of 6.53, while those for E. crus-galli ranged from 6.15 g to 16.06 g a.i. ha-1, giving a BSI of 2.61. Our findings suggest that E. oryzicola has a greater potential risk than E. crus-galli for the development of metabolism-based resistance to florpyrauxifen-benzyl.

Fumigant Toxicity of Phenylpropanoids Identified in Asarum sieboldii Aerial Parts to Lycoriella ingenua (Diptera: Sciaridae) and Coboldia fuscipes (Diptera: Scatopsidae).

Lycoriella ingenua (Dufour) (Diptera: Sciaridae) and Coboldia fuscipes (Meigen) (Diptera: Scatopsidae) are two of the most economically important insect pests of cultivated mushrooms. The toxicities to the fly larvae of the three phenylpropanoids (methyleugenol, myristicin, and safrole) from aerial parts of Asarum sieboldii Miquel (Aristolochiaceae) were compared with those of the currently available carbamate insecticide benfuracarb. In a contact+fumigant mortality bioassay with L. ingenua and C. fuscipes larvae, methyleugenol (1.46 and 2.33 µg/cm2) was the most toxic compound, followed by safrole (2.03 and 2.59 µg/cm2) and myristicin (3.59 and 4.96 µg/cm2), based on 24-h LC50 values. The phenylpropanoids were less toxic than benfuracarb (LC50, 0.75 and 0.55 µg/cm2). In vapor-phase mortality tests with the larvae, the phenylpropanoids were consistently more toxic in closed versus open containers, indicating that the effect of the compounds was largely a result of vapor action. Global efforts to reduce the level of highly toxic synthetic insecticides in the agricultural environment justify further studies on A. sieboldii plant-derived products as potential fumigants for the control of mushroom fly populations in mushroom houses and mushroom compost.

Acaricidal activity of plant essential oils against Dermanyssus gallinae (Acari: Dermanyssidae).

The acaricial activity of 56 plant essential oils against poultry house-collected adult Dermanyssus gallinae De Geer was examined using direct contact and fumigation methods. In a filter paper contact bioassay, 100% mortality at 0.07 mgcm-2 was observed in bay, cade, cinnamon, clove bud, coriander, horseradish, lime dis 5F, mustard, pennyroyal, pimento berry, spearmint, thyme red and thyme white oils, whereas the mortality of these oils was significantly decreased at 0.02 mgcm-2. In fumigation tests with adult D. gallinae at 0.28 mgcm-2, cade, clove bud, coriander, horseradish and mustard oils were more effective in closed containers than in open ones, indicating that the effect of these essential oils was largely due to action in the vapour phase. Plant essential oils described herein merit further study as potential D. gallinae control agents.