Ingestion of Novaluron Elicits Transovarial Activity in Stephanitis pyrioides (Hemiptera: Tingidae)

Comparative study of three plant-derived extracts as new management strategies against Spodoptera littoralis (Boisd.) (Lepidoptera: Noctuidae)

Finding innovative eco-friendly agents for pest control may be aided by investigating the plant-derived extracts' properties on economic pests. Therefore, the insecticidal, behavioral, biological and biochemical effects of Magnolia grandiflora (Magnoliaceae) leaf water and methanol extracts, Schinus terebinthifolius (Anacardiaceae) wood methanol extract, and Salix babylonica (Salicaceae) leaf methanol extract in comparison with a reference insecticide novaluron against S. littoralis were evaluated. The extracts were analyzed by High-Performance Liquid Chromatography (HPLC). The most abundant phenolic compounds were 4-hydroxybenzoic acid (7.16 mg/mL) and ferulic acid (6.34 mg/mL) in M. grandiflora leaf water extract; catechol (13.05 mg/mL), ferulic acid (11.87 mg/mL), and chlorogenic acid (10.33 mg/mL) in M. grandiflora leaf methanol extract; ferulic acid (14.81 mg/mL), caffeic acid (5.61 mg/mL), and gallic acid (5.07 mg/mL) In the S. terebinthifolius extract; cinnamic acid (11.36 mg/mL), and protocatechuic acid (10.33 mg/mL) In the methanol extract from S. babylonica extract. S. terebinthifolius extract had a highly toxic effect against second larvae after 96 h and eggs with LC₅₀ values of 0.89 and 0.94 mg/L, respectively. Despite M. grandiflora extracts didn't show any toxicity against S. littoralis stages, they had an attractant effect on fourth- and second larvae, with feeding deterrence values of - 2.7% and - 6.7%, respectively, at 10 mg/L. S. terebinthifolius extract significantly reduced the percentage of pupation, adult emergence, hatchability, and fecundity, with values of 60.2%, 56.7%, 35.3%, and 105.4 eggs/female, respectively. Novaluron and S. terebinthifolius extract drastically inhibited the activities of α-amylase and total proteases to 1.16 and 0.52, and 1.47 and 0.65 ΔOD/mg protein/min, respectively. In the semi-field experiment, the residual toxicity of tested extracts on S. littoralis gradually decreased over time compared to novaluron. These findings indicate that extract from S. terebinthifolius is a promising insecticidal agent against S. littoralis.

Insect growth regulators elicit transovarial effects on Teleonemia scrupulosa (Hemiptera: Tingidae)

BACKGROUND

Lantana lace bug, Teleonemia scrupulosa Stål (Hemiptera: Tingidae), is an important insect pest of lantana (Lantana camara L.). The adults and nymphs feed on the leaves, gradually deteriorating the quality of leaf tissue, as the affected leaves appear brown and desiccated. Infestations of T. scrupulosa reduce the market value of container plants in nurseries and the aesthetic value of ornamental landscapes. Because T. scrupulosa typically is managed using neonicotinoids and concerns related to the nontargeted effects of neonicotinoids on pollinators are mounting, practitioners are seeking alternative options to manage T. scrupulosa infestations. Insect growth regulators (IGRs) elicit transovarial activity, where adults exposed to IGRs produce nonviable eggs, but this effect has not been documented for T. scrupulosa.

RESULTS

A significantly lower number of T. scrupulosa nymphs was produced when adults were sprayed topically with novaluron and pyriproxyfen than nontreated adults. The number of T. scrupulosa nymphs produced was not significantly different when adults were exposed to a lower dose (0.125×) and a maximum dose (1.0×) of novaluron.

CONCLUSION

Novaluron and pyriproxyfen elicited transovarial effects on T. scrupulosa when adults were exposed to these IGRs. Evidence of transovarial effects was demonstrated when T. scrupulosa adults were exposed to lower doses (≤0.125×) than the maximum label dose, as densities of nymphs were similar between the lower doses and the maximum label dose of novaluron.

Reproductive toxicity of Novaluron in Bombyx mori (Lepidoptera: Bombycidae) and its impact on egg production

Bombyx mori was used as a model to evaluate the reproductive toxicity of Novaluron in insects. Morphological analyses of the testes and ovaries of B. mori throughout their life cycle revealed important alterations in the germ and somatic cells involved in spermatogenesis and oogenesis. We observed in all testicular developmental phases that Novaluron affected not only the organization, distribution and development of the cysts containing male germ cells, but also the morphological features of cell death. Similar cellular characteristics were found in the treated B. mori ovaries, suggesting the occurrence of cell death in both organs, in addition to a significant reduction in oviposition of eggs by female moths. We demonstrated reproductive toxicity of Novaluron to the nontarget beneficial insect silkworm, thus providing a theoretical basis for revealing the reproductive toxicity of this insecticide to other nontarget beneficial insects.

Effect of Benzoylphenyl Ureas on Survival and Reproduction of the Lace Bug, Leptopharsa gibbicarina

Simple Summary

Pestalotiopsis fungal complex is a disease that causes damages in oil palm (Elaeis guineensis), and the lace bug, Leptopharsa gibbicarina is the main insect pest that spread this disease. Application of neurotoxic insecticides has been a common method used to control L. gibbicarina for decades in Colombia and Venezuela. The effects of four benzoylphenyl ureas (BPUs) (lufenuron, novaluron, teflubenzuron, and triflumuron) were assessed against L. gibbicarina for toxicity, survival, and reproduction. Overall, the results show that novaluron, teflubenzuron, and triflumuron cause high mortality and reduce survival time, fecundity, and fertility. Thus, BPUs exhibit detrimental effects on L. gibbicarina and can be used as alternatives to other chemical insecticides.

Abstract

The lace bug, Leptopharsa gibbicarina is a vector of Pestalotiopsis fungal complex in oil palm crops in the Americas. The effects of four benzoylphenyl ureas (BPUs) (lufenuron, novaluron, teflubenzuron, and triflumuron) were evaluated against L. gibbicarina for toxicity, survival, reproduction, and mortality in semi-field conditions. Concentration-mortality bioassays demonstrated that novaluron (LC₅₀ = 0.33 ppm), teflubenzuron (LC₅₀ = 0.24 ppm), lufenuron (LC₅₀ = 0.17 ppm), and triflumuron (LC₅₀ = 0.42 ppm) are toxic to L. gibbicarina nymphs. The survival rate was 99% in control nymphs, decreasing to 50% in nymphs exposed to LC₅₀ of triflumuron, 47% in nymphs treated with lufenuron, 43% in nymphs treated with teflubenzuron, and 43% in those treated with novaluron. Sublethal concentrations of BPUs showed detrimental effects on the adult emergence, longevity, fecundity, and fertility of this insect. The mortality of nymphs caused by these insecticides was similar in both laboratory and semi-field conditions. Our results suggest that novaluron, teflubenzuron, and triflumuron are highly effective against L. gibbicarina, and therefore, have potential applications for this oil palm pest.

Residual Efficacy of Novaluron Applied on Concrete, Metal, and Wood for the Control of Stored Product Coleopteran Pests

Simple Summary

Insect pests of stored commodities cause harm not only to bulk grains but also to many value-added food products in mills, processing plants, and other facilities where these products are stored. In this study, the residual efficacy of an Insect Growth Regulator (IGR), novaluron, was evaluated under laboratory conditions against larvae of three stored product insects, Oryzaephilus surinamensis (L.), Triboliumcastaneum (Herbst), and Trogoderma granarium Everts, on concrete, metal, and wood surfaces to which IGRs are typically applied for pest control in such facilities. Statistically significant reductions in emergence percentages of adults compared to a distilled water control occurred for up to 12 weeks when novaluron was sprayed on concrete, metal, and wood at rates between 0.053 and 0.209 mg/m², the highest of which induces 100% mortality at 0 weeks after treatment. Residual efficacy decreased with increasing time after treatment due to degradation and sorption of novaluron into the surfaces. Novaluron residues were most persistent on metal and least persistent on wood surfaces. Knowledge of novaluron residual efficacy on storage facility surfaces can be helpful guidance for timing of postharvest insect pest management treatments as the costs of commonly used pesticides increase along with insect resistance to such pesticides.

Abstract

The residual efficacy of novaluron on concrete, metal and wood was evaluated against last-instar larvae of Oryzaephilus surinamensis (L.), Triboliumcastaneum (Herbst), and Trogoderma granarium Everts. The larvae and food provided for survival were exposed to surfaces pretreated at rates of 0.053, to 0.209 mg/m² and bioassays were conducted from 0- to 16-weeks post-treatment. Percentage emergence of adults was recorded after 30 days (d). On all surfaces at week 0, no O. surinamensis or T.castaneum adults emerged, and ≤3.3% emergence of T. granarium was found at 0.209 mg/m². Novaluron significantly reduced the percentage emergence of adults of the three species compared to a distilled water control for the first 12 weeks on all the tested surfaces as the residual efficacy declined at a low rate during initial weeks and then at a high rate in the final weeks of the 16-week study. Reductions to emergence were most persistent on metal surfaces, with mean percentages of adult emergence of ≤18.3 in week 12, followed by concrete (≤32.5) and wood (≤45.0) for all species at novaluron application rates of 0.209 mg/m². For >4-weeks protection, higher application rates would be needed to avoid buildup of pest populations and reductions in profitability. Such results can be helpful for the management of O. surinamensis, T.castaneum, and T. granarium as the costs of commonly used insecticides against postharvest insect pests and the resistance of these insects to the pesticides gradually increase in mills, warehouses, and food storage facilities.