Chemotaxis response and age-stage, two-sex life table of the Cheilomenes sexmaculata (Fabricius) (Coccinellidae: Coleoptera) against different aphid species.

The Cheilomenes sexmaculata (Fabricius) (Coleoptera: Coccinellidae), is one of the most beneficial and identifiable predators of numerous soft-bodied and sucking insect pests of several crops. Biological parameters and olfactory response of C. sexmaculata were investigated under laboratory conditions by providing three different aphid species i.e., mustard aphid (Lipaphis erysimi Kaltenbach), citrus black aphid (Toxoptera citricida Kirkaldy), and peach aphid (Diuraphis noxia Kurdjumov) as a food source. The developmental period of immature stages of C. sexmaculata was shorter on D. noxia as compared to other aphid species. The adult longevities were longer on D. noxia and T. citricida while shorter on L. erysimi. Female fecundity was highest on D. noxia while lowest on L. erysimi. Life table parameters i.e., intrinsic rate of increase (r), finite rate of increase (λ), net reproductive rate (Ro), and gross reproductive rate (GRR) were maximum on D. noxia while minimum on L. erysimi. The mean generation time C. sexmaculata was 20.90, 23.69, and 26.2 days on D. noxia, L. erysimi, T. and citricida, respectively. These findings were further confirmed from the olfactory experiment where D. noxia proved to be the most preferred prey. This study provides necessary information for mass-rearing of C. sexmaculata.

Toxicology of diatomaceous earth, phyto oils and their admixed emulsions against adults of Tribolium castaneum (Herbst).

Tribolium castaneum (Herbst), one of the invasive stored pest, is resistant to the most of synthetic insecticides used against this it. Moreover, synthetic insecticides are a major threat to human health, the environment, and the ecosystem. The development of some smart tools is needed to minimize the use of hazardous chemicals. As an alternative, nano-insecticides are on the horizon. Emulsions are expressed as sustain release of insecticidal components to achieve maximum efficacy and low residual toxicity. In this study, some essential oils (Cymbopogon citratus (DC.) Stapf, Ocimum basilicum L., Curcuma longa L., and Trachyspermum ammi L.), diatomaceous earth (DE), and their nano-emulsions are evaluated against T. castaneum. Essential oils and DE were tested at four (60 ppm, 30 ppm, 15 ppm, 7.5 ppm) different concentrations with and without emulsions, and data was recorded after 6, 12, 24, 48, and 72 h of exposure respectively. The mortality observed in essential oils of C. citratus, O. basilicum, and C. longa without emulsion after 72 h of treatment at the highest concentration was 98%, 95%, and 85%, respectively. While, at the highest concentration the lowest mortalities were observed with DE and T. ammi i.e. 65%. Insecticidal activity of emulsion essential oils increased to 100%, 98%, 90%, and 68.3% for C. longa, C. citratus, O. basilicum, and T. ammi, respectively. The results support that these admixed emulsions could be used as an alternative to synthetic insecticides in conventional formulations.

Graphene quantum dots as cysteine protease nanocarriers against stored grain insect pests.

Storing grains remain vulnerable to insect pest attack. The present study developed a biopesticide using biomolecules and their encapsulation in nanoparticles. A 25 kDa cysteine protease extracted from seeds of Albizia procera (ApCP) was encapsulated in graphene quantum dots (GQDs). The insecticidal activity of ApCP, with or without GQDs, against two stored grain insect pests, Tribolium castaneum (Herbst) and Rhyzopertha dominica (Fabricius) was explored. Insects were exposed to three concentrations 7.0, 3.5 and 1.7 mg of ApCP per a gram of wheat flour and grains. The insecticidal activity of ApCP encapsulated with GQDs was improved compared to that of ApCP without GQDs for both insect pests. The number of eggs and larvae of T. castaneum was reduced by 49% and 86%, respectively. Larval mortality was increased to 72%, and adult eclosion of T. castaneum was reduced by 98% at a 7.0 mg/g concentration of ApCP with GQDs compared to that of ApCP without GQDs. Exposure to 7.0 mg/g ApCP with GQDs, the number of R. dominica eggs and larvae was reduced by 72% and 92% respectively, larval mortality was increased by 90%, and eclosion was reduced by 97%. The extraction, purification, characterization, quantification and encapsulation of ApCP with GQDs were also studied. Cysteine protease nanocarriers have the potential to control stored grain insect pests.

Fitness parameters of Plutella xylostella (L.) (Lepidoptera; Plutellidae) at four constant temperatures by using age-stage, two-sex life tables.

Different temperature zones have significant impact on the population dynamics of Plutella xylostella. Effective management of P. xylostella requires the knowledge of temperature tolerance by different life stages. In the current study, fitness parameters of diamondback moth were reported by using age-stage, two-sex life table traits at four constant temperatures (15, 20, 25 and 30 °C). The life cycle of P. xylostella was significantly longer at 15 °C. The 20 °C level of temperature was found optimal for fecundity, gross reproductive rate (51.74 offspring) and net reproductive rate (44.35 offspring per individual). The adult pre-oviposition period was statistically at par at all four level of temperatures. However, the survival was maximum at 20 °C as compared to other three temperature ranges. Based on the current study, it was concluded that temperature has a great role in population build-up of P. xylostella and effective management tactics should be applied to prevent significant damage to cabbage and other cruciferous crops when the temperature in the field is near 20 °C.

Toxic effects of some insecticides, herbicides, and plant essential oils against Tribolium confusum Jacquelin du val (Insecta: Coleoptera: Tenebrionidae).

Cereals are staple food for many countries and are grown on millions of hectares of land, but much of the harvest is wasted due to losses by pests. To minimize these losses, many pesticides are used which are damaging to the environment and human health. There are debates to get rid of these chemicals but they are still in use at large scale. An alternative control strategy for insect pests in storage houses is the use of botanicals. In this study, four plant essential oils, two plant extracts, two herbicides, and two insecticides were used against Tribolium confusum and the comparison of toxicity was made by calculating LC50 and LT50 values. LC50 values were higher for abamectin (2.09-10.23 mg/L) and cypermethrin (3.41-11.78 mg/L) insecticides followed by neem essential oil (7.39-19.24 mg/L) and citrus extract (10.14-24.50 mg/L). However, LC50 values were maximum in case of jaman plant extract (22.38-176.42 mg/L) followed by two herbicides, Logran (19.66-39.72 mg/L) and Topik (29.09-47.67 mg/L) However, LC50 values were higher for topic herbicide (24.098 ppm) and jaman essential oil (16.383 ppm) after four days of treatment. Abamectin and cypermethrin insecticides, neem essential oil and citrus plant extract also killed adults of T. confusum quicker as compared other essential oils, extracts and herbicides. Results revealed that botanical formulations being environmentally safe could be used instead of highly hazardous pesticides for stored products' pests. This study also elaborates the non-host toxicity of herbicides commonly applied in our agroecosystem.