Bioactivity of formulas containing essential oils from the family Myrtaceae for the management of deltamethrin-resistant Plutella xylostella (L.) (Lepidoptera: Plutellidae)

Plutella xylostella is the major pest of Brassica and is resistant to more than 95 synthetic insecticides, including deltamethrin, which is frequently used in family farming activities in the state of Pernambuco, Brazil. A possible strategy for overcoming such resistance is the use of botanical insecticides containing essential oils. The aim of the present study was to determine the chemical composition of essential oils from Syzygium aromaticum, Melaleuca alternifolia, Melaleuca leucadendra, Eucalyptus citriodora and Eucalyptus globulus and evaluate the effects of these oils as well as selected constituents (β-pinene, α-terpinene, ρ-cymene, limonene, 1,8-cineole, γ-terpinolene, citronellal, terpinen-4-ol, eugenol, β-caryophyllene and E-nerolidol) on different stages of development of two populations of P. xylostella – one susceptible and one resistant to deltamethrin. Chemical analysis by gas chromatography-mass spectrometry revealed eugenol (S. aromaticum), 1,8-cineole (E. globulus), citronellal (E. citriodora), terpinen-4-ol (M. alternifolia) and E-nerolidol (M. leucadendra) to be the major constituents. Among the oils tested, S. aromaticum was the most promising in the different modes of action and had the same level of toxicity to the two populations of P. xylostella analyzed. Among the constituents, E-nerolidol and terpinen-4-ol exhibited promising larvicidal action, whereas limonene exhibited promising ovicidal and antifeedant action. None of the oils presented severe phytotoxicity to the host plant. All results were compared to those achieved with deltamethrin and azadirachtin, which were used as positive controls. The deltamethrin-resistant population of P. xylostella did not exhibit pre-adaptive resistance to the oil from S. aromaticum or E-nerolidol, terpinen-4-ol and limonene.

     

Arthropods on grapes benefit more from fungicide reduction than from organic farming

BACKGROUND

Pesticides are considered main contributors to global arthropod declines and therefore may decrease the provision of ecosystem services such as natural pest control. Organic farming and cultivating pest- and disease-resistant varieties can allow pesticide applications and their impacts on nontarget organisms and the environment to be reduced. We investigated the effects of organic versus conventional management and fungus-resistant versus susceptible wine grape varieties on arthropod biodiversity and pest control of grape berry moths in 32 vineyards in the Palatinate region, Germany. Hazard quotients of applied pesticides were calculated for each vineyard.

RESULTS

The cultivation of fungus-resistant varieties led to significantly reduced hazard quotients and in turn enhanced abundances of natural enemies, particularly theridiid and philodromid spiders. Unexpectedly, organic management resulted in higher hazard quotients than conventional management and reduced numbers of natural enemies, particularly earwigs. Pest predation rates showed no significant differences between grape varieties or management types.

CONCLUSION

Widespread benefits of organic management on arthropod biodiversity found in other crops were absent in our viticultural study region. This is likely due to the dominant role of fungal diseases in viticulture, which requires high numbers of fungicide treatments under both conventional and organic viticulture. Thus, fungicide reduction through the cultivation of fungus-resistant grape varieties is one key element to fostering the abundance of arthropods in general and beneficial arthropods in particular. Beyond vineyards, this is potentially relevant in numerous other crop types. © 2023 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.     

Antimicrobial testing of selected fluoroquinolones against Pseudomonas aeruginosa isolated from canine otitis

A total of 100 Pseudomonas aeruginosa (P. aeruginosa) isolates were collected over a 1.5-year period from cases of canine otitis. Sensitivities to enrofloxacin, marbofloxacin, and orbifloxacin were determined using minimum inhibitory concentration testing (MICT). Isolates were also tested for sensitivities to enrofloxacin and marbofloxacin using disk-diffusion susceptibility testing (DDST). Isolates were significantly more sensitive to marbofloxacin than to enrofloxacin (z = -4.57; P<0.05) or orbifloxacin (z = -5.02; P<0.05). Agreement was 87% between MICT and DDST for marbofloxacin, with approximately equal numbers of overestimation and underestimation errors. Agreement was 74% between MICT and DDST for enrofloxacin, but DDST tended to overestimate the number of enrofloxacin-susceptible strains. These results suggest that marbofloxacin is more effective against P. aeruginosa than either enrofloxacin or orbifloxacin and that relying on DDST may lead to ineffective enrofloxacin treatment.     

Comparison of chloroform-methanol-extracted and solvent-free triglyceride determinations in four fish species

Lipids, including triglycerides, are important variables in fish bioenergetics and can be used to estimate overall fish condition. Triglycerides are the major energy storage form in fish and therefore are a more ecologically and physiologically relevant measure of bioenergetics than total lipids. Chloroform-methanol-extracted total body lipids (Bligh and Dyer) and total body triglycerides determined in chloroform-methanol extracts and unextracted whole-body fractions were measured in four fish species: northern pike Esox lucius, burbot Lota lota, slimy sculpin Cottus cognatus, and spottail shiners Notropis hudsonius. Determinations of total body lipids were consistently greater than those of total body triglycerides when measured in the same solvent-extracted fraction, although both measures followed similar trends. In an effort to eliminate the need for extraction with organic solvents, we compared the performance of an enzyme-based triglyceride assay in both the solvent-extracted fraction and a whole-body unextracted homogenate for each fish. The chloroform-methanol-extracted triglyceride values were consistently lower than triglycerides measured in the unextracted whole-body homogenate. In addition, comparison of triglyceride measurements revealed limitations to the solvent extraction and subsequent triglyceride determinations in lean fish. Thus, in addition to being simple, rapid, and not requiring organic solvents, determination of triglycerides in an unextracted whole-fish homogenate may be a useful alternative to chloroform-methanol-based methods of lipid extraction and subsequent triglyceride measurement.     

Identifying the problem weeds of rice‐based systems along the inland‐valley catena in the southern Guinea Savanna,Africa

While weeds generally are considered as the most important overarching production constraints in inland‐valley cropping systems in West Africa, little is known about species' associations with environmental and crop management factors. Weed species' associations with seasonal and environmental factors, such as their position on the catena, soils and cropping systems, were studied during two seasons (dry and wet) in 45 arable fields of three inland valleys in south‐western Benin, Africa. The three most dominant weed species were Dactyloctenium aegyptium, Commelina benghalensis and Digitaria horizontalis on the inland‐valley crests (uplands), Ludwigia hyssopifolia, Corchorus aestuans and Ludwigia octovalvis on the sloping hydromorphic fringes and Leersia hexandra, Ipomoea aquatica and Fimbristylis ferruginea in the valley bottoms (lowlands). Echinochloa colona, Cleome viscosa and Talinum triangulare were the three most dominant species in the dry‐season crops (maize or vegetables) and Leer. hexandra, I. aquatica and Sphenoclea zeylanica were the three most dominant species in the wet‐season crop (rice). Ageratum conyzoides, Synedrella nodiflora and D. horizontalis were observed throughout the catena. Problem weeds in inland‐valley agro‐ecosystems are those that combine a high frequency with a high submergence tolerance and ecological plasticity, C₄ grasses, perennial C₃ species with persistent root structures and broad‐leaved species with high propagation rates. Weed management strategies that are aimed at increasing the resilience of rice‐based cropping systems in the inland valleys of the southern Guinea Savanna of Africa should address the categories of problem species that were identified in this study. This can be done best by following an integrated approach, including the use of more weed‐competitive cultivars and rotation crops.     

Contribution of Seafood to Total Vitamin B12 Intake and Status of Young Adult Men and Women

Previous research suggests 20% of omnivores and 40% of vegetarians do not consume enough vitamin B12. The contribution of seafood to dietary B12 intake stratified by frequency of seafood consumption and B12 status of young adults was assessed. Seafood was the greatest contributor to B12 intake (31%) among nonvegetarians, and intake comparisons based on frequency of seafood consumption revealed that frequent seafood consumers had higher (p < 0.001) B12 intakes. None of the frequent seafood consumers had suboptimal status, which occurred mainly in subjects consuming seafood < 1 time/month and vegetarians. Our findings suggest that modest seafood intake contributes to maintaining normal B12 status.     

DETERMINING THE IMPACT OF CRAWFISH IMPORTS ON U.S. DOMESTIC PRICES

The study identifies the linkage between imports and the domestic price of crawfish. The results show a simultaneous increase in imports and domestic prices of crawfish while showing a negative relationship between domestic landings and price. Each model shows that there is a seasonality effect on the domestic price of crawfish. The study also shows that increases in the domestic supplies of shrimp, tilapia, and clams generated increases in the domestic crawfish price, while increases in imported and domestic supplies of beef and imported supplies of pork decreased the domestic crawfish price.     

The efficacy of MS‐222 as anaesthetic agent in four freshwater aquarium fish species

The efficacy of anaesthetic tricaine methanesulfonate (MS‐222) was evaluated in four freshwater aquarium fish species, Zebrafish (Danio rerio), Guppy (Poecilia reticulata), Discu (Symphysodon discus) and Green swordtail (Xiphophorus helleri). The correct dose of anaesthetic should induce the plane 4 of anaesthesia in less than 180 s, recovery in less than 300 s and must survive when exposed during 30 min to anaesthetic. Fishes were exposed to six concentrations of anaesthetic (75, 100, 125, 150, 200 and 250 mg L^?1) and the time of fish reaching plane 4 of anaesthesia, post exposure recovery, and the percentage of survival when fish were subject to 30 min in the anaesthetic were recorded. The optimal doses varied according to the species: D. rerio – 75, 100 and 125 mg L^?1, P. reticulata – 125, 150 and 200 mg L^?1, S. discus – 75 and 100 mg L^?1 and X. helleri – 125 and 150 mg L^?1. The induction time generally decreased significantly with increasing concentration of MS‐222 for all of the species evaluated. The recovery time had a tendency to increase with the increase of the MS‐222 concentration for D. rerio, P. reticulata and S. discus. On the other hand, X. helleri recovery time decreased with the increase of MS‐222 concentration. MS‐222 proved to be effective in anaesthesia for all the freshwater ornamental species studied. The main results clearly show that the optimal dose to anesthetize is fish species dependent and it is completely wrong to extrapolate optimal anaesthetic concentrations between different species.     

Population characteristics of channel catfish near the northern edge of their distribution: implications for management

Channel catfish, Ictalurus punctatus (Rafinesque), populations in six lakes in northern Idaho, USA, were sampled to describe their population characteristics. During the summers of 2011 and 2012, 4864 channel catfish were sampled. Channel catfish populations had low to moderate catch rates, and length structure was dominated by fish <400 mm. Channel catfish were in good body condition. All populations were maintained by stocking age‐1 or age‐2 fish. Growth of fish reared in thermally enriched environments prior to stocking was fast compared to other North American channel catfish populations. After stocking, growth of channel catfish declined rapidly. Once stocked, cold water temperatures, prey resources and (or) genetic capabilities limited growth. Total annual mortality of age 2 and older channel catfish was generally <40%. Tag returns indicated that angler exploitation was low, varying from 0 to 43% among lakes. This research provides insight on factors regulating channel catfish population dynamics and highlights important considerations associated with their ecology and management.