Extending the Shelf-Life of <i>Myrothecium verrucaria</i>, a Bioherbicide

Abstract

The shelf-life of a bioherbicide product is an important factor with regard to its commercial potential. The bioherbicidal efficacy of freshly fermented Myrothecium verrucaria (strain IMI 368023) (MV) mycelia formulations and MV mycelia preparations that had been freeze-dried and then stored at −20˚C for 8 years was compared. Two concentrations of each formulation (1.0x and 0.5x) were tested, utilizing bioassays on seedlings of the weed, hemp sesbania (Sesbania exaltata) under greenhouse conditions or in darkness utilizing hydroponically grown seedlings. Freeze drying of freshly prepared MV mycelium produced a light, brownish-colored powder. Efficacy tests of this reconstituted 8-year-old dried material showed that some bioherbicidal activity was lost during long-term storage, i.e., ~20% and ~60% seedling dry weight reduction at the 1.0x and 0.5x rate, respectively. Although plant mortality was greater in the fresh mycelial preparations treatments versus the freeze-dried and stored samples at all time points in the time-course, the stored material still caused >80% mortality, 15 days after treatment. Comparative disease progression ratings also showed a similar trend. Overall results show that freeze-drying MV is a useful method to reduce the bulk and cumbersomeness of storing heavy liquid fermentation product, while retaining bioherbicidal activity. These findings increase the utility of this bioherbicide and offer the potential to use the dried material in soil treatments or in a more concentrated form than attainable via the fermented product.

Bioherbicidal Activity of Albifimbria verrucaria (Formerly Myrothecium verrucaria) on Glyphosate-Resistant Conyza canadensis

“…In contrast, a dew duration period of only 16 h resulted in relatively high (80%) control of cocklebur (Xanthium strumarium) plants treated with another Xanthomonas strain [54,55]. No plant mortality occurred at ≤4 h of dew [51] and mature plants were more resistant to infection than younger plants [55]. In the present studies, no dew was applied in the greenhouse tests, although plants in the field test did receive intermittent dew and some light rain (<0.20 cm) during testing.…”

“…Cultures of AV (formerly M. verrucaria (IMI 368023)) were maintained on potato dextrose agar (PDA) (Difco Laboratories, Inc., Detroit, MI, USA) in petri dishes at 25 • C. Mycelial cultures of AV were prepared via fermentation and used as previously described [50,51].…”

The potential future roles of natural compounds and microbial bioherbicides in weed management in crops

“…These include a limited shelf life and more limited storage conditions, lack of compatibility with other pesticides, and the need for a specific, well-defined microenvironment for the microbe to infect the target weed. Shelf life and storage conditions can be improved by formulation (Amsellem et al, 1999;Zidack, Quimby, 2002), freeze drying (Hoagland et al, 2017), and by low temperatures and a modified atmosphere in the packaging (Teshler et al, 2007). These problems are less with viral, microbial bioherbicides such as Tobacco mild green mosaic virus for control of tropical soda apple (Solanum viarum) (Charudattan, 2007).…”