Behavioural responses and changes in biology of rice leaffolder following treatment with a combination of bacterial toxins and botanical insecticides

Ingestion of the bacterial toxins Bacillus thuringiensis (Berliner) sub sp kurstaki, neem seed kernel extract and Vitex negundo L. (Lamiales:Verbenaceae) leaf extract to the rice leaffolder (RLF), Cnaphalocrocis medinalis (Guenée) (Lepidoptera: Pyralidae), resulted in altered leaf-folding behaviour and biology. In laboratory experiments, treatment with plant extracts and bacterial toxins suppressed leaf folding behaviour of C. medinalis. Larvae fed lower doses moulted into progressive instars, but in the late fourth to early fifth instars, spinning behaviour completely stopped, feeding was reduced and larvae regurgitated a sticky, semisolid substance that occluded the tunnel in which the pupae were formed. With the combination of Btk and botanicals, average leaf consumption was decreased by a factor of two even at reduced concentrations when compared with controls. Duration of larval and pupal stages, adult longevity and fecundity were more affected by treatment with the combination of bacterial toxins and both botanicals than by the treatment with the bacterial toxins or botanicals individually. All larvae died in the treatment of bacterial toxins and both botanicals combined.     

The toxicity and behavioural effects of neem limonoids on Cnaphalocrocis medinalis (Guenée), the rice leaffolder

Meliaceae plant products have been shown to exert pesticidal properties against a variety of insect species. In agricultural pest control programs, such products may have the potential to be used successfully as botanical insecticides. The effect of the neem (Azadirachta indica) limonoids azadirachtin, salannin, deacetylgedunin, gedunin, 17-hydroxyazadiradione and deacetylnimbin on the biology and mortality of rice leaffolder larvae was investigated. In laboratory experiments, treatment with neem limonoids suppressed leaf folding behaviour of C. medinalis. Biological parameters (larval duration, pupal duration adult longevity and fecundity) were also affected by the treatment. Azadirachtin, salannin, and deacetylgedunin showed high bioactivity at all doses, while the rest of the neem limonoids were less active, and were only biologically active at high doses. Azadirachtin was most potent in all experiments and produced almost 100% larval mortality at 1 ppm concentration. These results indicate neem limonoids affect the larval behaviour. These effects are most pronounced in early instars.     

The toxicity and physiological effect of goniothalamin, a styryl-pyrone, on the generalist herbivore, Spodoptera exigua Hübner

Efficacy of Goniothalamin a styryl-pyrone isolated from Goniothalamus wightii Hook.f. and Thoms, against beet armyworm, Spodoptera exigua (Hübner), populations was determined under laboratory condition. The experiments were carried out with concentrations of 5, 10, 15 and 30 ppm in an artificial diet and compared with control insects. Laboratory bioassay showed that the goniothalamin had a strong effect on food utilization, moulting and gut histology. The food consumption and conversion of ingested and digested food to body matter decreased with increasing pyrone concentration. The antifeedant activity was also observed in larvae of S. exigua. The treated third instar larvae exhibited mortality in a dose dependent manner. At 5, 10, 15 and 30 ppm/insect, the pyrone gave 23%, 45% 63% and 100% mortality respectively. The larvae of S. exigua gained significantly less weight until pupation in the 10 and 15 ppm pyrone concentrations. Duration of larval period was also affected after treatment with pyrone. The metamorphosis was delayed with additional moulting (7th instar) after treatment with 10 and 15 ppm of goniothalamin, the percentage of larvae successfully moulted into progressive instars was significantly decreased with an increase in pyrone concentrations. The effects of goniothalamin on midgut ultrastructure of third instar larvae of S. exigua were investigated by using light microscopy. Cross sections of the midgut showed that the epithelial cells were destroyed. Significant damage of the midgut epithelium was observed along with lysis.     

Microplastic sources,formation, toxicity and remediation: a review

Microplastic pollution is becoming a major issue for human health due to the recent discovery of microplastics in most ecosystems. Here, we review the sources, formation, occurrence, toxicity and remediation methods of microplastics. We distinguish ocean-based and land-based sources of microplastics. Microplastics have been found in biological samples such as faeces, sputum, saliva, blood and placenta. Cancer, intestinal, pulmonary, cardiovascular, infectious and inflammatory diseases are induced or mediated by microplastics. Microplastic exposure during pregnancy and maternal period is also discussed. Remediation methods include coagulation, membrane bioreactors, sand filtration, adsorption, photocatalytic degradation, electrocoagulation and magnetic separation. Control strategies comprise reducing plastic usage, behavioural change, and using biodegradable plastics. Global plastic production has risen dramatically over the past 70 years to reach 359 million tonnes. China is the world's top producer, contributing 17.5% to global production, while Turkey generates the most plastic waste in the Mediterranean region, at 144 tonnes per day. Microplastics comprise 75% of marine waste, with land-based sources responsible for 80–90% of pollution, while ocean-based sources account for only 10–20%. Microplastics induce toxic effects on humans and animals, such as cytotoxicity, immune response, oxidative stress, barrier attributes, and genotoxicity, even at minimal dosages of 10 μg/mL. Ingestion of microplastics by marine animals results in alterations in gastrointestinal tract physiology, immune system depression, oxidative stress, cytotoxicity, differential gene expression, and growth inhibition. Furthermore, bioaccumulation of microplastics in the tissues of aquatic organisms can have adverse effects on the aquatic ecosystem, with potential transmission of microplastics to humans and birds. Changing individual behaviours and governmental actions, such as implementing bans, taxes, or pricing on plastic carrier bags, has significantly reduced plastic consumption to 8–85% in various countries worldwide. The microplastic minimisation approach follows an upside-down pyramid, starting with prevention, followed by reducing, reusing, recycling, recovering, and ending with disposal as the least preferable option.

     

Effect of neem limonoids on lactate dehydrogenase (LDH) of the rice leaffolder, Cnaphalocrocis medinalis (Guenée) (Insecta: Lepidoptera: Pyralidae)

Neem is derived from the neem tree Azadirachta indica A. Juss. (Meliaceae), and its primary insecticidal component is the tetranortriterpenoid azadirachtin and other limonoids. The effect of neem limonoids azadirachtin, salannin, deacetylgedunin, gedunin, 17-hydroxyazadiradione and deacetylnimbin on enzyme lactate dehydrogenase (LDH) activity of the rice leaffolder (RLF) Cnaphalocrocis medinalis (Lepidoptera: Pyralidae) larvae was investigated. There was a decrease in enzyme activity relative to the control at all concentrations tested. When fed a diet of rice leaves treated with neem limonoids in bioassays, gut tissue enzyme, LDH levels in rice leaffolder larvae are affected. These results indicate neem limonoids affect LDH activity. These effects are most pronounced in early instar larvae. Azadirachtin was the most potent in of all the limonoids in all experiments indicating strong enzyme inhibition. Clear dose-response relationships were established with respect to LDH activity.     

Larvicidal and repellent activity of N-methyl-1-adamantylamine and oleic acid a major derivative of bael tree ethanol leaf extracts against dengue mosquito vector and their biosafety on natural predator

Environmental Science and Pollution Research - Aegle marmelos (L.) Correa belongs to the family Rutaceae is generally known as “bael fruit tree” occuring across the south Asian...