Efficacy of Beauveria bassiana and Beauveria pseudobassiana isolates against the pine processionary moth, Thaumetopoea wilkinsoni Tams, 1926 (Lepidoptera/Notodontidae)

Background The pine processionary moth, Thaumetopoea wilkinsoni Tams, 1926 (Lepidoptera/Notodontidae) is one of the most harmful insects that destroys pine ecosystems by feeding on pine leaves at its larval stage. Because of its urticating setae, the insect also causes severe skin reactions to animals and humans. Instead of chemical control, eco-friendly biological control methods are preferred to combat this species. Results The purpose of this study was to evaluate the efficacy of five different Beauveria bassiana Vuill, 1912 (Hypocreales/Cordycipitaceae) isolates (TR-SM-10, TR-SM-11, TR-SM-2, TR-SK-1 and TR-D-1) and one B. pseudobassiana Rehner & Humber (Hypocreales/Cordycipitaceae) isolate (TR-SM-1) against the fourth instar larvae of T. wilkinsoni under laboratory conditions. T. wilkinsoni larvae were collected from the Ondokuz Mayıs University Kurupelit Campus in Samsun, Turkey, in 2021, and the fourth instar larvae were used in the experiment. Two ml of spray of the six fungal isolates were applied to every ten larvae at each concentration (1 × 107 and 1 × 108 conidia ml−1). The experiment was carried out in five replicates per group, and the larvae were observed for 10 days. As a result, all isolates of B. bassiana caused 100% mortality at 1 × 108 conidia ml−1 concentration. B. pseudobassiana isolate also caused 100% mortality at both concentrations. At 1 × 107 conidia ml−1 concentration, the larvae treated with the B. pseudobassiana isolate (TR-SM-1) had the lowest LT50 (2.89 days) and LT90 values (4.79 days), while the larvae treated with TR-SM-10 isolate had the highest LT50 (5.65 days) and LT90 values (9.39 days). At 1 × 108 conidia ml−1 concentration, the larvae treated with TR-SK-1 isolate had the lowest LT50 (2.89 days) and LT90 values (4.79 days), while those treated with TR-SM-10 isolate had the highest LT50 (3.95 days) and LT90 values (8.15 days). Conclusion It has been recommended that the five different isolates of B. bassiana and B. pseudobassiana isolates were virulent to T. wilkinsoni larvae and can be used for biological control of T. wilkinsoni.

Detection of Zika virus in Anopheles stephensi Liston, 1901 (Diptera: Culicidae) in India - First report

Zika virus (ZIKV) a mosquito-borne, causing acute febrile illness associated with rash, arthralgia and conjunctivitis in the patient, was reported from Thiruvananthapuram, Kerala, as an outbreak with 83 cases. Entomological surveillance revealed the presence of aedine mosquitoes viz., Aedes aegypti (Linnaeus, 1762), Ae. albopictus (Skuse, 1894) and Ae. vittatus (Bigot, 1861) and nonaedine mosquitoes viz., Anopheles stephensi Liston,1901, Mansonia uniformis (Theobald, 1901), Culex tritaeniorhynchus Giles, 1901 and Cx. gelidus Theobald,1901. Aedes (Ae. aegypti, Ae. vittatus and Ae. Albopictus) mosquito larvae were high in the Zika affected areas. Moreover ZIKV was detected in An. stephensi mosquitoes collected from Parassala, Thiruvananthapuram (the native place of the first ZIKV confirmed case in the present outbreak in Kerala). Molecular diagnostics of Ae. Aegypti, Ae. vittatu and An. stephensi mosquitoes revealed that the species were loaded with ZIKV. Significantly this is the first ever report of ZIKV detecting in An. stephensi in the world. Aedes adults (male and female) and An. stephensi emerged from fourth instar larvae and pupae were found to have ZIKV, indicating transovarial transmission of the virus.

Bioactivities of Lamiaceae, Myristicaceae, and Myrtaceae plant oils against Nilaparvata lugens Stâl. (Hemiptera: Delphacidae)

Essential oil (EO) plants have properties as botanical insecticides. Some of them come from the families of Lamiaceae, Myristicaceae, and Myrtaceae. A plant belonging to the Lamiaceae includes patchouli (Pogostemon cablin), while the Myristicaceae includes nutmeg (Myristica fragrans), and the Myrtaceae includes clove (Syzygium aromaticum) and cajuput (Melaleuca cajuput subsp. cajuputi). This research aimed to evaluate toxicity, feeding inhibition, and oviposition deterrent from four EO plants from the Lamiaceae, Myristicaceae, and Myrtaceae to brown rice planthopper Nilaparvata lugens (Hemiptera: Delphacidae), the main pest of rice. The results showed that cajuput and patchouli oil gave more potent toxicity to N. lugens with LC50 and LC95 were 0.016% and 4.87% for cajuput oil and 0.019% and 5.25% for patchouli oil. Cajuput oil at 0.002% deterred oviposition 51.74% and inhibited feeding on 0.016% as many as 71.52% with strong enough criteria to the fourth instar nymphs of N. lugens. Patchouli oil deterred oviposition from 0.002% as much as 61.15% and inhibited feeding on 0.019% as many as 68.73% with strong enough criteria. The highest oviposition deterrent was 83.2% on patchouli oil at the concentration of 0.188%, whereas the highest feeding inhibition was 82.78% on cajuput oil at the concentration of 0.169%.

Stage-specific expression of an odorant receptor underlies olfactory behavioral plasticity in Spodoptera littoralis larvae

Background The detection of environmental cues and signals via the sensory system directs behavioral choices in diverse organisms. Insect larvae rely on input from the chemosensory system, mainly olfaction, for locating food sources. In several lepidopteran species, foraging behavior and food preferences change across larval instars; however, the molecular mechanisms underlying such behavioral plasticity during larval development are not fully understood. Here, we hypothesize that expression patterns of odorant receptors (ORs) change during development, as a possible mechanism influencing instar-specific olfactory-guided behavior and food preferences. Results We investigated the expression patterns of ORs in larvae of the cotton leafworm Spodoptera littoralis between the first and fourth instar and revealed that some of the ORs show instar-specific expression. We functionally characterized one OR expressed in the first instar, SlitOR40, as responding to the plant volatile, β-caryophyllene and its isomer α-humulene. In agreement with the proposed hypothesis, we showed that first but not fourth instar larvae responded behaviorally to β-caryophyllene and α-humulene. Moreover, knocking out this odorant receptor via CRISPR-Cas9, we confirmed that instar-specific responses towards its cognate ligands rely on the expression of SlitOR40. Conclusion Our results provide evidence that larvae of S. littoralis change their peripheral olfactory system during development. Furthermore, our data demonstrate an unprecedented instar-specific behavioral plasticity mediated by an OR, and knocking out this OR disrupts larval behavioral plasticity. The ecological relevance of such behavioral plasticity for S. littoralis remains to be elucidated, but our results demonstrate an olfactory mechanism underlying this plasticity in foraging behavior during larval development.

Experiments on invertebrate predation on cladocerans and its relationships with lake data

Until recently, knowledge of the impact of invertebrate predators on cladocerans in the Brazilian Lake Monte Alegre was limited to a few species. In order to assess the effects of predation on other cladoceran species, experiments were carried out with different pair-wise combinations of prey species. The experiments tested predation by fourth instar larvae of the dipteran Chaoborus brasiliensis Theobald on neonates and adults of the cladocerans Daphnia gessneri Herbst, Diaphanosoma birgei Kořínek, and Ceriodaphnia richardi Sars, and predation by the water mite Krendowskia sp. on neonates and adults of C. richardi and D. gessneri. In replicated treatments, the prey was offered alone or in combination with neonates and adults of two species and kept in bottles on a plankton wheel under controlled temperature, photoperiod, and light conditions. Chaoborus larvae preyed on neonates of D. birgei and D. gessneri and on adults of the former species. They preyed preferentially on neonates and adults of D. birgei over neonates and adults of C. richardi. The mite Krendowskia sp. preyed on only one species: neonates and adults of D. gessneri. Data on the distribution and strategies of prey in the lake are discussed in light of the experimental results, in an attempt to establish a link between laboratory data and field conditions.

The Effect of Lemongrass Leaves and Stalks Extracts using Methanol as The Eco-friendly Larvicides on Fourth Instar Aedes aegypti Larvae

BACKGROUND: Aedes aegypti is one of the most vicious mosquitoes, known for its role in several deadly diseases, including dengue fever and Zika. Several strategies have been developed over decades to prevent vector-borne diseases; one of them is insecticide to control the mosquito population. However, this strategy would not last long due to the elevation of resistance, environmental problem, and some issues regarding human health. Natural products have become major options to combat the glitches. Lemongrass (Cymbopogon citratus) has known for its toxic effect on mosquito larva. AIM: The objective of this study was to assess the effect of C. citratus extract against fourth instar of A. aegypti larvae. METHODS: Three extract concentrations, 2.5%, 5%, and 7.5%, were used. The larvicide activity was evaluated at 2, 4, and 6 h. Our data indicated that all concentrations contributed to increase larvae mortality. RESULTS: Lethal Concentration (LC) 50 and LC90 were achieved at 2.5% and 4.1% of extract, respectively. CONCLUSION: C. citratus extract has a larvicide activity against fourth instar of A. aegypti.

Toxicity, Sublethal and Low Dose Effects of Imidacloprid and Deltamethrin on the Aphidophagous Predator Ceratomegilla undecimnotata (Coleoptera: Coccinellidae)

Ceratomegilla undecimnotata (Coleoptera: Coccinellidae) is a common aphidophagous coccinellid predator used in biological control against aphid pests. Knowing toxicity, lethal, and sublethal effects of insecticides on natural enemies is essential in order to incorporate them into Integrated Pest Management (IPM). In the present study, the lethal and sublethal effects of imidacloprid and deltamethrin were evaluated on the fourth instar larvae of C. undecimnotata and subsequently on the full life cycle. Our results strongly suggest that sublethal and low doses of imidacloprid and deltamethrin at LD10 and LD30 affected fourth instar larvae duration time, adult preoviposition period, total preoviposition period, and fecundity. Moreover, the intrinsic (r) and finite (λ) rate of increase and the net reproduction rate (R0) significantly decreased in populations treated with imidacloprid compared to the control population. The data clearly suggest that imidacloprid and deltamethrin have a negative influence on population growth parameters of C. undecimnotata at sublethal and low doses and, therefore, these insecticides should be used with caution within the context of IPM.

The way to maturity: taxonomic study on immatures of Southern Brazilian Coccinellini (Coleoptera: Coccinellidae) species important in biological control

Among the predatory ladybird beetles (Coccinellidae: Coleoptera), members of the Coccinellini, predators of aphids and psyllids, stand out. Although the beneficial status of these beetles has been acknowledged by biological control researchers, there are no keys or detailed studies on the immature stages of South American Coccinellidae, especially Coccinellini. We provide descriptions and illustrations of the immatures and adults of major predatory Coccinellini species in southern Brazil along with an identification key for fourth instar larvae and pupae. The following species are included: Cycloneda sanguinea (Linnaeus, 1763), Eriopis connexa (Germar, 1824), Harmonia axyridis (Pallas, 1773), Hippodamia convergens Guérin-Méneville, 1842 and Olla v-nigrum (Mulsant, 1866). The morphological study, which included the use of scanning electron microscopy, revealed new characters such as the type of tarsal claws, spiracles, chalazae, parascoli and strumae. The identification key provided here may be useful in biological control programs.