Efficacy of Essential Oils from Ocimum kenyense as a Biopesticide against Aphis gosypii, Thrips tabaci and Bemisia tabaci.

Natural sources of biopesticides such as plants and microorganisms are widely employed for pest management globally. Over the last five decades, the use of biopesticides has been explored as a safer alternative to synthetic pesticides. This study determined the repellence and contact toxicity of essential oils from Ocimum kenyense plant against Thrips tabaci, Bemisia tabaci, and Aphis gosypii. The essential oils (Eos) were extracted from dry leaves by hydrodistillation using the Clevenger apparatus for 8 hours. The composition of essential oils was qualitatively and quantitatively analysed using GC-MS, while ATR-FTIR was used to determine the functional groups. The major compound ion in the Eos was 1,8-Cionele while the major phytochemical identified was Eucalyptol Bioassay of the crude extracts were carried out on T. tabaci, B. tabaci, and A. gosypii. Contact toxicity and repellency tests against mixed-sex adult pests were carried out on T. tabaci, B. tabaci, and A. gosypii. In contact toxicity, five different concentrations were prepared and each was replicated five times. Acetone was used as a negative control, while permethrin, a commercial chemical pesticide was used as a positive control. The LD50 of the essential oils was determined by Probit analysis SPSS version 26.0. The response to the treatments was observed after 24 hours by using a blunt object probing and the pests that did not respond were counted as dead. It was found that essential oils from O. kenyense had the lowest LD50 of 0.127 µL against A. gosypii. This implies that O. kenyense can be used as a contact toxicant against A. gosypii. Repellency tests were carried out at four different concentrations. N, N-Diethyltoluamide (DEET) repellent from a commercial mosquito repellent was used to compare the effectiveness of the essential oils against commercial repellents. The repellency test responses were observed after 1 hour and the data was used to determine the correlation between different levels of concentration of Eos and percentage repellency of Eos of O. kenyense leaves carried out at α=0.05. There was a high correlation of 1.000 between the increase in concentration of Eos and repellency against A. gosypii, T. tabaci and B. tabaci. The results were statistically significant and (P<0.05, α=0.05). Therefore, essential oils from O. kenyense can be used as a contact toxicant biopesticide against A. gosypii and a repellent biopesticide against A. gosypii, T. tabaci and B. tabaci.

Potentials of compost, compost tea and aqueous neem leaves extract in reducing some diseased plants and boosting onion (Allium cepa L.) production in the field at Gapring-Lara in t he Department of Mayo Kani (Cameroon)

With a view to promoting the onion sector, we studied the behavior of onion following the application in fields of Cow Dung compost, compost tea and the aqueous extract of neem leaves during the 2018/2019 and 2019/2020 growing seasons. The device used was a complete randomized block comprising 10 treatments including compost (Cp), compost tea (CpT), Neem extract (Nex), compost + compost tea (Cp+CpT),compost+Neem extract (Cp+Nex), compost tea+Neem extract (CpT+Nex), compost+Compost Tea+NeemExtract (Cp+CpT+Nex), Control (Ctrl), Chemical Pesticide (ChP) and Chemical Fertilizer (ChF) with 3 repetitions each. The work focused on agronomic and phytopathological parameters. The results reveal that Cp+CpT+Nex treatment had a highly significant influence on the germination rate (92.33%) than Ctrl treatment (44%). He was significantly increased the number of leaves, size and yield compared to other treatments with 22.16 leaves, 52 cm and 114.74 t/ha (2018/2019) and 20.83 leaves and 53.84 cm; but yield was higher by ChF with 47.49 t/ha (2019/2020). Nex, Cp+Nex and CpT+Nex treatments reduced attack of Delia antiqua compared to control. And significant reduction in number of plants attacked by onion mildew was observed in Cp+CpT+Nex treatment. In view of the results obtained, organics fertilizers can be used in onion production.

An investigation of the genotoxic and cytotoxic effects of myclobutanil fungicide on plants

Myclobutanil is a chemical pesticide commonly used in the production of some vegetables and fruits like greenhouse peppers, grapes, and apples. The aim of this study was to investigate the genotoxic and cytotoxic effects of myclobutanil fungicide on the Allium cepa plant, the model organism. Randomly amplified polymorphic DNA and inter simple sequence repeat-PCR techniques were performed on the DNA of A. cepa exposed to the different myclobutanil doses and time periods. The nucleus anomalies and abnormal anaphases were investigated using a light microscope. PCR analyses showed that myclobutanil causes some DNA sequence changes on the onion genome depending on the increase in the fungicide dose and exposure time. It was determined that myclobutanil has a serious genotoxic effect, even in low doses like 25–50 ppm.

The Role of Yeasts as Biocontrol Agents for Pathogenic Fungi on Postharvest Grapes: A Review

In view of the growing concern about the impact of synthetic fungicides on human health and the environment, several government bodies have decided to ban them. As a result, a great number of studies have been carried out in recent decades with the aim of finding a biological alternative to inhibit the growth of fungal pathogens. In order to avoid the large losses of fruit and vegetables that these pathogens cause every year, the biological alternative’s efficacy should be the same as that of a chemical pesticide. In this review, the main studies discussed concern Saccharomyces and non-Saccharomyces yeasts as potential antagonists against phytopathogenic fungi of the genera Penicillium and Aspergillus and the species Botrytis cinerea on table grapes, wine grapes, and raisins.

Response of Entomopathogenic Fungus Paecilomyces fumosoroseus on Drought Stress Factor

The entomopathogenic fungus Paecilomyces fumosoroseus (common name: Isaria fumosorosea) can utilize to control white fly population. Bemisia tabaci or white fly has become key pest in soybean cultivation. It reported became resistance due to chemical pesticide. Some of new strain has been emerge as chemical pesticide resultant However, to develop P. fumosoroseus as biopesticide hide a problem. The environmental drought factor (temperature and water stress) become major problem. This research aimed to determine effect of environmental factor like temperature and water stress to growth and effectivity of P. fumosoroseus, due to selection an isolat were persist to drought factor. In this research has been used two different isolat of P. fumosoroseus, that is Wirowongso 1 isolat and Mumbulsari 5 isolates. This research had been conducted with five different treatments. First is a growth test under temperature stress, in vitro germination test under temperature stress and in vitro germination test under water stress, and virulence test under temperature and under water stress. The result showed that the increase a temperature and of water stress, directly make decreased of growth, germination and effectively. That effect has made different effect to growth, germination and effectivity on both isolat. The results showed that the isolat WR 1 test result showed the isolat WR 1 more persist to each drought factor. It became more valuable to develop as biopesticide among other.Keywords: Bemicia tabaci, germination, isolat, Isaria fumosorosea, in-vivo.

Integrated pest management for Jatropha Carcus plant: An Impulsive control approach

In this research, an integrated pest management model using impulsive differential equations has been investigated for Jatropha curcas plantation to control its natural pests through relying on the release of infective pest individuals and spraying of chemical pesticides. Using Floquet’s theory and the small amplitude perturbation method, it is obtained that there exists an asymptotically stable susceptible pest eradication periodic solution when the release amount of infected pest is larger than the critical maximum value (or strength of chemical pesticide spraying is larger than some critical maximum value). Also, we have established the permanence of the system. After comparison, it is explored that integrated pest management is more effective than biological control or chemical control. Finally, verify the analytical results through numerical simulation.

Ecological strategies of biological and chemical control agents on wildfire disease of tobacco (Nicotiana tabacum L.)

Background To investigate the ecological effects of chemical and biological control methods on tobacco wildfire disease, a plot field experiment was conducted to compare the control efficiency and mechanisms of a chemical pesticide (kasugamycin wettable powder, KWP) and a biological control agent (BCA) through high-throughput sequencing of bacterial 16S rRNA genes. Results The results showed that the BCA displayed better performance in decreasing the disease index and morbidity of tobacco than the chemical pesticide. By monitoring the endophytic community within tobacco leaves, it was found that the control effects of these two methods might be mediated by different changes in the endophytic bacterial communities and community assembly patterns. The application of either method decreased the taxonomic diversity of the leaf endophytic community. Compared to the BCA, KWP showed a more significant effect on the endophytic community structure, while the endophytic community treated with the BCA was able to return to the original state, which presented much lower disease infection. The disease control efficiency of KWP and BCA treatments might be achieved by increasing the abundance of Sphingomonas and Streptophyta, respectively. Furthermore, an analysis of the ecological processes in community assembly indicated that the BCA strengthened the homogeneous and variable selection, while KWP enhanced ecological drift. Conclusions The results suggested different control mechanisms between KWP and BCA treatments, which will help in developing diverse ecological strategies for plant disease control.

Control strategies for heterogeneous plant pathogens: evolutionary and agricultural consequences

Optimising the use of chemical pesticide is required in order to reduce the inevitable environmental and economic costs related to it. The consequences of chemical control are particularly tricky to foresee in the presence of pathogens, displaying heterogeneous traits involved in their life cycle, because its effect will likely differ across the population. In this work, we investigate the effects of trait-dependent pesticide on heterogeneous plant pathogens, by means of a minimal model connecting evolutionary and agricultural states of the system. We model a pathogen population displaying continuous levels of virulence and transmission. Control strategies are modelled by the quantity of pesticide released and its degree of correlation with the pathogen's heterogeneous traits. We show that the pathogen population can adapt towards opposite evolutionary states, that may be reversed by chemical control due to its heterogeneous selective pressure. This dual behaviour triggers saturating effects in yield production, with respect to pesticide use. As a consequence, we show that maximising yield production and minimising pesticide application are conflicting objectives. We identify Pareto-efficient solutions, where the optimal pesticide type depends on the applied quantity. Our results provide a theoretical framework to explore how to harness heterogeneity in pathogen populations to our advantage.