Temporal synergism can enhance carbamate and neonicotinoid insecticidal activity against resistant crop pests

BACKGROUND: Piperonyl butoxide (PBO) effectively synergises synthetic pyrethroids, rendering even very resistant insect pests susceptible, provided a temporal element is included between exposure to synergist and insecticide. This concept is now applied to carbamates and neonicotinoids. RESULTS: A microencapsulated formulation of PBO and pirimicarb reduced the resistance factor in a clone of Myzus persicae (Sulzer) from >19 000- to 100-fold and in Aphis gossypii (Glover) from >48 000- to 30-fold. Similar results were obtained for a strain of Bemisia tabaci Gennadius resistant to imidacloprid and acetamiprid, although a second resistant strain did not exhibit such a dramatic reduction, presumably owing to the presence of target-site insensitivity and the absence of metabolic resistance. Synergism was also observed in laboratory susceptible insects, suggesting that, even when detoxification is not enhanced, there is degradation of insecticides by the background enzymes. Use of an analogue of PBO, which inhibits esterases but has reduced potency against microsomal oxidases, suggests that acetamiprid resistance in whiteflies is largely oxidase based. CONCLUSION: Temporal synergism can effectively enhance the activity of carbamates and neonicotinoids against resistant insect pests. Although the extent of this enhancement is dependent upon the resistance mechanisms present, inhibition of background enzymes can confer increased sensitivity against target-site resistance as well as increased metabolism. .     

Temporal synergism by microencapsulation of piperonyl butoxide and alpha-cypermethrin overcomes insecticide resistance in crop pests

A microencapsulated formulation that gives a burst release of piperonyl butoxide (PBO) several hours before a burst release of a conventional pyrethroid can effectively overcome metabolic resistance in Bemisia tabaci Gennadius, Helicoverpa armigera (Hübner), Aphis gossypii Glover and Myzus persicae Sulzer. This increase in efficacy against resistant pests was reflected in a field trial against B. tabaci on cotton, eliminating the need for two treatments. The ratio between the active insecticide and the synergist was found to be crucial in reducing resistance factors.     

Use of a wireless system to measure invasive arterial blood pressure in ponies – preliminary study

Objective  To evaluate the feasibility and functionality of intra-carotid wireless device implantation in ponies, and to investigate its short-term complications.
Study design  Prospective preliminary study.
Animals  Five mixed breed, adult, intact male ponies weighing 104 ± 28.8 kg (mean ± SD) underwent surgery. Arterial blood pressure data were continuously collected from four animals.
Methods  General anesthesia was induced on two consecutive days. On the first day, an intra-arterial wireless device was implanted in the right carotid artery. On the next day, a transcutaneous intra-arterial catheter was placed in the left facial artery. Data from both sources were collected. Post-mortem examination was performed.
Results  Surgical time was 27.1 ± 11.85 minutes. All catheters remained in place with some extra vascular migration. Complications included mild seroma and hematoma.
Conclusion  The wireless system allowed continuous monitoring in ponies throughout anesthesia and at rest and may allow for the recording of arterial blood pressure and heart rate when it would be difficult to achieve with a conventional system (e.g. during recovery from anesthesia).
Clinical relevance  The wireless invasive blood pressure monitor may allow continuous measurements when only intermittent measurements would be feasible with a wired system.     

Ultrasound emission in infant rats as an indicant of arousal during appetitive learning and extinction

Infant rats rewarded for crawling by being allowed to suckle on the dry nipple of an anesthetized dam showed a decreasing rate of ultrasound production during acquisition and an increasing rate during extinction. These results suggest that infant rats can be stressed and are aroused as a result of successive nonrewards just as adult rats are. In addition, these results do not support the hypothesis that infant rats lack inhibitory mechanisms related to poorly developed neural centers.     

Effects of post-harvest storage of Allium sativum bulbs on the cryopreservation of stem-discs by encapsulation/dehydration

Summary

Cryostorage of vegetatively propagated Allium species is important for the long-term conservation and sustainable use of Allium germplasm. Cryopreservation of clonally-propagated crops such as Allium is a complex, multicomponent process where both cryogenic and non-cryogenic factors can influence the outcome of storage. This study demonstrates that the duration of post-harvest storage of bulbs significantly affected the frequency of shoot regrowth following cryostorage of Allium sativum. Post-cryostorage survival of stem-disc quarters was highest (75%) following a storage period of 5 months. The highest frequency of regrowth (55%), after 4 months of storage, corresponded to an average regeneration frequency of 1.9 shoots per stem-disc quarter. These results show the importance of the physiological state of bulbs, and the need to optimise the duration of storage to break bulb dormancy, in order to improve the cryopreservation of A. sativum stem-discs using encapsulation/dehydration.     

Investigating the potential of selected natural compounds to increase the potency of pyrethrum against houseflies Muscadomestica (Diptera: Muscidae)

BACKGROUND: A study was undertaken to determine the efficacy of seven natural compounds compared with piperonyl butoxide (PBO) in synergising pyrethrum, with the intention of formulating an effective natural synergist with pyrethrum for use in the organic crop market. RESULTS: Discriminating dose bioassays showed PBO to be significantly more effective at synergising pyrethrum in houseflies than the seven natural compounds tested, causing 100% mortality in insecticide‐susceptible WHO and resistant 381zb strains of housefly. The most effective natural synergists against WHO houseflies were dillapiole oil, grapefruit oil and parsley seed oil, with 59, 50 and 41% mortality respectively, compared with 18% mortality with unsynergised pyrethrum. Against 381zb houseflies, the most effective natural synergists were parsley seed oil and dillapiole oil. Esterase inhibition by the natural compounds and PBO in vitro showed no correlation with pyrethrum synergism in vivo, whereas the inhibition of oxidases in vitro more closely correlated with pyrethrum synergism in vivo. CONCLUSION: Dillapiole oil and parsley seed oil showed the greatest potential as pyrethrum synergists. PBO remained the most effective synergist, possibly owing to its surfactant properties, enhancing penetration of pyrethrins. The results suggest the involvement of oxidases in pyrethroid resistance in houseflies, with the efficacy of synergists showing a high correlation with inhibition of oxidases. Copyright © 2011 Society of Chemical Industry