Fifteen volatiles released by red raspberries and strawberries during ripening were analyzed for the inhibition of postharvest decay fungi. Five compounds completely inhibited all fungi directly on fruit at 0.4 μL/mL., Of these, benzaldehyde at 0.04 μL/mL completely inhibited isolated cultures of Alternaria altemata, Botrytis cinerea, and Col‐Ietotrichum gloeosporioides, while 1‐hexanol, E‐2‐hexenal and 2‐non‐anone inhibited all three fungal species at 0.1 μL/mL. When added directly to media, 0.1% (v/v) benzaldehyde or E‐2‐hexenal inhibited all three species. Starch encapsulated 2‐nonanone reduced fungal decay of raspberries and strawberries in enclosed containers after 7 days at 10°C.
This study describes the identification of an aggregation pheromone for the pepper weevil,Anthonomus eugenii and field trials of a synthetic pheromone blend. Volatile collections and gas chromatography revealed the presence of six male-specific compounds. These compounds were identified using chromatographic and spectral techniques as: (Z)-2-(3,3-dimethylcyclohexylidene)ethanol, (E)-2-(3,3-dimethylcyclohexylidene)ethanol, (Z)-(3,3-dimethylcyclohexylidene)acetaldehyde, (E)-(3,3-dimethylcyclohexylidene)acetaldehyde, (E)-3,7-dimethyl-2,6-octadienoic acid (geranic acid), and (E)-3,7-dimethyl-2,6-octadien-1-ol (geraniol). The emission rates of these compounds from feeding males were determined to be about: 7.2, 4.8, 0.45, 0.30, 2.0, and 0.30µg/male/day, respectively. Sticky traps baited with a synthetic blend of these compounds captured more pepper weevils (both sexes) than did unbaited control traps or pheromone-baited boll weevil traps. Commercial and laboratory formulations of the synthetic pheromone were both attractive. However, the commercial formulation did not release geranic acid properly, and geranic acid is necessary for full activity. The pheromones of the pepper weevil and the boll weevil are compared. Improvements for increasing trap efficiency and possible uses for the pepper weevil pheromone are discussed. A convenient method for purifying geranic acid is also described.
Formulations of Bacillus thuTingiensis Berliner spores and crystals, encapsulated together within a starch matrix containing no ultraviolet screens, lost all spore viability and insecticidal activity against the European corn borer, OstTinia nubilalis (Hiibner), within 4 d. Encapsulated crystals and spores with Congo red or folic acid as screens exhibited moderate spore viability and retained at least 50% of their original toxicity after 12 d. Congo red was the most effective protectant, followed by folic acid and para amino benzoic acid. Because Bacillus thuTingiensis is likely sensitive to the entire ultraviolet-component in sunlight, ability to provide broad-band ultraviolet protection is required to prolong insecticidal activity effectively.
The effect of sunlight and simulated rain on the residual insecticidal activity of Bacillus thuringiensis subsp. kurstaki formulations applied to field grown cabbage were measured. Leaf samples were collected 1, 2, 4, and 7 d after treatment and assayed against neonate cabbage looper, Trichoplusia ni (Hubner). Simulated rain applied by a sprinkler irrigation system washed B. thuringiensis from the plants, causing on average 20% reduction in insecticidal activity across all treatments. Sunlight intensity was manipulated by applying degrees of shade treatments consisting of no cover, clear plastic covers, and black plastic covers. Black plastic provided protection from sunlight degradation for 7 d, whereas both clear plastic and no cover treatments lost insecticidal activity equally beginning 2 d after application of B. thuringiensis. There was no interaction between simulated rain and shade treatments and thus no synergistic loss of insecticidal activity by the combination of both environmental factors. Formulations of B. thuringiensis differed in their ability to resist wash-off by simulated rain and degradation by sunlight. Formulations consisting of 1% wt:vol gluten or 0.5% wt:vol casein resisted wash-off better than f1our/ sucrose (2% wt:vol) and Dipel 2X. Resistance to sunlight degradation was greatest with the gluten formulation and progressively less for casein, flour / sucrose and Dipel2X formulations. Half-life of insecticidal activity in response to sunlight was calculated to be 7.1, 5.7, 4.8, and 4.3 d for gluten, casein, flour/ sucrose and Dipel 2X formulations, respectively.
Nuclear polyhedrosis viruses such as the one isolated from the celery looper, Anagrapha falcifera (Kirby) (AfMNPV), have the potential to be successful bioinsecticides if improved formulations can prevent rapid loss of insecticidal activity from environmental conditions such as sunlight and rainfall. We tested 16 spray-dried formulations of AfMNPV to determine the effect of different ingredients (e.g., lignin, corn flour, and so on) on insecticidal activity after simulated rain and simulated sunlight (at Peoria, IL) and natural sunlight exposures (at Tifton, GA). The most effective formulation contained pregelatinized corn flour and potassium lignate, which retained more than half of its original activity after 5 cm of simulated rain, and almost full activity after 8 h of simulated sunlight. In Georgia, formulations made with and without lignin were compared for persistence of insecticidal activity when exposed to natural sunlight. In addition, the effect of fluorescent brighteners as formulation components and spray tank additives was tested. Results showed that the formulations with lignin had more insecticidal activity remaining after sunlight exposure than formulations without lignin. The inclusion of brighteners in the formulation did not improve initial activity or virus persistence. However, a 1% tank mix significantly enhanced activity and improved persistence. Scanning electron micrographs revealed discreet particles, and transmission electron micrographs showed virus embedded within microgranules. Results demonstrated that formulations made with natural ingredients could improve persistence of virus-based biopesticides.
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