Validation of a multi-residue method to determine deltamethrin and alpha-cypermethrin in mosquito nets by gas chromatography with electron capture detection (GC-µECD)

Background: Nowadays long-lasting insecticidal mosquito nets (LNs) are frequently used around the world to protect people against malaria vectors. As they contain insecticide, laboratory control is needed to check whether the content of the active ingredient follows the conditions of the manufacturer and also if the active ingredient is still present after some time of use. For this purpose, an analytical method had to be developed. The fact that LNs include a range of polymers for the yarn and use coated or incorporated technologies for the active ingredient, it is a challenge to find only one analytical method determining the active ingredient in LNs, which takes into account both impregnation technologies. Some methods are provided by international organizations but are limited by the determination of only one pesticide per method. The aim of this study was to optimize a short time extraction method for deltamethrin and alpha-cypermethrin from coated and incorporated mosquito nets and also to detect both insecticides in one analytical run, using gas chromatography with electron capture detection (GC-mu ECD). Methods: Based on the literature, the most suitable solvent and the adequate extraction process for the insecticides used for net making were identified and adapted for the new multi-residue method. Results: The validation data of the multi-residue method to determine deltamethrin and alpha-cypermethrin in mosquito nets by GC-mu ECD are given. Depending on the concentration of the active ingredient spiked on the nets, the mean recovery for alpha-cypermethrin ranged between 86% and 107% with a relative standard deviation below 3.5%. For deltamethrin it ranged between 90% and 108% with a relative standard deviation also below 3.5%. The limit of detection is 0.009 g.a.i/kg of net (0.3 mg a.i./m(2) of net) both for alpha-cypermethrin and deltamethrin. Conclusions: Data obtained are excellent. A 30 minutes reflux extraction method with xylene was developed to determine alpha-cypermethrin and deltamethrin in long-lasting insecticidal mosquito nets (LNs) by gas chromatography with electron capture detection (GC-mu ECD). The method can be easily extended to others pyrethroid used for mosquito net treatment. This paper also presents an overview of the studies dealing with pesticide determination in mosquito nets

Absence of effects of herbicides use on yam rots : a case study in Wulensi, Ghana

Yam farmers in Ghana have, over the years, used herbicides for weed control, particularly glyphosate. Although this has been helpful to them, there are complaints and concerns, among the yam farmers and a section of the public, that the yam tuber rots easily under the use of herbicides. This study, therefore, was set up at the field level to investigate the possibility of herbicides use causing yam rot. Two yam varieties, laribako and olodo, were grown under the conditions of chemical weed control (use of glyphosate) and manual weed control in three replicate sites in Wulensi in the Nanumba traditional area of northern Ghana. The study revealed that there was no difference in rots between herbicide treated yams and manually weeded yams, but that there was a difference in rots between laribako and olodo yam varieties. The results also showed that there was no difference in yield between herbicide treated yams and manually weeded yams. Based on the findings, it can be concluded that, there was no difference in yam rot and yield between herbicides treated and manually weeded yams, but laribako was more susceptible to rot than olodo

Insecticide effect of zeolites on the tomato leafminer Tuta absoluta (Lepidoptera: Gelechiidae)

(1) Background: The tomato leafminer Tuta absoluta (Lepidoptera: Gelechiidae) is a key tomato insect pest. At present, it is considered to be a serious threat in various countries in Europe, North Africa, and Middle East. The extensive use and the developed resistance of T. absoluta to spinosad causes some concern, which leads to the need for alternative products. (2) Materials and Methods: Several laboratory experiments were conducted to investigate the ovicidal properties of a zeolite particle film on T. absoluta. The toxicity of three different zeolites and six zeolite formulations to T. absoluta eggs and larvae was determined using different exposure methods. (3) Results: In general, the formulated zeolites yielded higher egg and larvae mortality values, especially when the zeolite particle film was residually applied. Notable differences in mortality rates from exposure to zeolites compared to other products, such as kaolin, its formulated product Surround, and the insecticide spinosad, were observed. Kaolin and Surround exhibited little or no effect for both application methods, while the hatch rate was reduced by 95% when spinosad was applied topically. Spinosad yielded egg and larvae mortality rates of 100% for both application methods. Additionally, increased oviposition activity was observed in adults exposed to the wettable powder (WP) formulations. These WP formulations increased egg deposition, while Surround and spinosad elicited a negative oviposition response. (4) Conclusions: It can be derived that the tested products, zeolites BEA (Beta polymorph A), FAU (Faujasite), LTA (Linde type A), and their formulations, had no real insecticidal activity against the eggs of T. absoluta. Nevertheless, egg exposure to zeolites seemed to affect the development process by weakening the first instar larvae and increasing their mortality. Subsequently, based on the choice test, no significant difference was observed between the number of eggs laid on the treated leaves and control leaves

Beneficial effects of zeolites on plant photosynthesis

A

Effect of adjuvants on the efficiency of dimethomorph plus mancozeb (Acrobat 2 kg:ha) on the control of late blight

Industrial adjuvants were tested in combination with dimethomorph plus mancozeb (Acrobat 2 kg/ha) in the field to investigate their efficacy on foliar late blight caused by Phytophthora infestans. The tested adjuvant fungicide treatments for late blight control were applied 5 times at 7-day intervals. The effect of the adjuvant fungicide treatments on epidemic development, tuber rot and blight incidence and tuber yields were determined. Last summer late blight development was arrested in July due to high temperatures and lasting drought. August was characterized by rather low temperatures and high rainfall. These weather conditions were very favourable for the development of late blight. Due to the heat waves of June and July the foliage started to die allready in Agust. Because of that no incidence of foliage blight was scored. No significant differences in yield were observed for the different treatments applied. The addition of an adjuvant had a clearly positive effect on the tuber yield. In the control 12,7 % infected tubers were observed. The mean tuber infection of plots sprayed with the Acrobat-adjuvant combinations was 7,4 %

Effect of adjuvants on the efficiency of benthiavalicarb plus mancozeb (Valbon 1.6 kg/ha) on the control of late blight in potato

Industrial adjuvants were tested in combination with benthiavalicarb plus mancozeb (Valbon 1.6 kg/ha) in the field to investigate their efficacy on foliar late blight caused by Phytophthora infestans. The tested adjuvant-fungicide treatments for late blight control were applied 6 times at 7-day intervals. The effect of the adjuvant-fungicide treatments on epidemic development, tuber blight and tuber yields were determined. Because of the favourable weather conditions a high disease pressure could be observed. The incidence of foliage blight was scored and at the end of the growing season the disease level was lower in plots sprayed with the Valbon-adjuvant combinations than in plots treated with only Valbon. The addition of an adjuvant had a clearly positive effect on the tuber yield although the differences were not significant. In the plots treated with Valbon 6.9 % infected tubers were observed. The mean tuber infection of plots sprayed with the Valbon-adjuvant combinations fluctuated between 2.3 and 15.6 %

Dynamic screening of agricultural contaminants in freshwater ecosystems as part of amphibian biodiversity conservation

C