azadirachtin and pyriproxyfen

Azadirachtin, as the most promising and effective botanical insecticide, exhibits significant growth inhibition activity against agricultural and forestry pests. However, its biochemical effects at the metabolic level compared with those of other insect growth regulators have not been studied. Therefore, in this study, a GC-MS based untargeted metabolomics approach was applied to compare azadirachtin with pyriproxyfen (a juvenile hormone analog) and tebufenozide (a molting hormone analog) in terms of their metabolic effects on Bactrocera dorsalis larvae. The bioactivity of azadirachtin against B. dorsalis larvae was significantly different than those of pyriproxyfen and tebufenozide. A total of 693 mass features were recognized, and 112 metabolites were identified in this study. The results showed that a total of 16, 13 and 10 differentially regulated metabolites corresponding to 12, 5 and 8 pathways occur in Aza versus CK, Pyr versus CK and Teb versus CK group, respectively. Further analysis showed that 6 differentially regulated metabolites corresponding to 5 key pathways could be the primary differential metabolic response of B. dorsalis larvae to the three insect growth regulators. The pathways were myo-inositol corresponding to ascorbate and aldarate metabolism as the specific response of B. dorsalis larvae to azadirachtin; xylitol, xylulose and 3-aminopropionitrile corresponding to pentose and glucuronate interconversions, and cyanoamino acid metabolism as the common responses to azadirachtin and pyriproxyfen; and 3-hydroxypropionic acid and beta-alanine corresponding to propanoate metabolism and beta-alanine metabolism as the specific responses to tebufenozide. The results showed that the metabolic response of B. dorsalis larvae to azadirachitin is closer to that of pyriproxyfen than tebufenozide. The differentially regulated metabolites and pathways responsible for this difference are discussed.

Topics: Animals; Hydrazines; Insect Hormones; Insecticides; Larva; Limonins; Metabolome; Metabolomics; Pyridines; Tephritidae

The extensive use of insecticides can cause adverse side effects on pollinators, which negatively impact crop productivity. The pollination carried out by the honeybee Apis mellifera L. (Hymenoptera: Apidae) is crucial in increasing the productivity of the melon (Cucumis melo L.). The main objective of this study was to assess if insecticides applied in the cultivation of cantaloupe melon exhibit significant levels of toxicity toward A. mellifera. We tested the toxicity of azadirachtin, pyriproxyfen, chlorantraniliprole, and imidacloprid, which are commonly sprayed to manage melon pests such as the whitefly Bemisia tabaci (Genn.) (Hemiptera: Aleyrodidae), the pickleworm Diaphania nitidalis (Stoll) and the melonworm Diaphania hyalinata (L.) (Lepidoptera: Pyralidae). Three treatments were carried out, 0.0×, 0.1x and 1.0x the concentration recommended by the manufacturer for the control of those pests. Repellency tests, analysis of mortality through contact and ingestion, and flight tests were performed. The insecticide imidacloprid caused mortality rates above 90% in all tested exposure pathways, displaying high residue persistence on plants. Although not causing significant mortality in the ingestion test, pyriproxyfen caused significant mortality after exposure through contact, and change in flight ability. Azadirachtin caused mortality in the ingestion test and impaired the flight ability of bees, while chlorantraniliprole only impaired the flight ability. Moreover, bees were not repelled by these insecticides, suggesting that they may collect contaminated food in the field while foraging. Altogether, ecofriendly, alternative pest control options should be developed, as well as the adoption of more selective insecticides, in order to reduce the non-target effects on honeybees and guarantee their pollination services.

Topics: Animals; Bees; Brazil; Cucurbitaceae; Flight, Animal; Insecticides; Lepidoptera; Limonins; Neonicotinoids; Nitro Compounds; Pest Control; Pollination; Pyridines

The lethal and sublethal effects of 11 insecticides on the predator Ceraeochrysa cubana (Hagen) were assessed under laboratory conditions. First-instar larvae and adults ≤ 48 h old were sprayed with the highest insecticides doses allowed to control Diaphorina citri Kuwayama in the citrus crop. The survival and duration rates of the different development stages, sex ratio, pre-oviposition period, fecundity, and fertility of the insects were evaluated. In the larval bioassay, chlorpyrifos and malathion had lethal effect which none larvae survived. Azadirachtin, lambda-cyhalothrin + chlorantraniliprole, lambda-cyhalothrin + thiamethoxam, and thiamethoxam had lethal and sublethal effects that did not allow to estimate the life table parameters because the low number of couples formed. Esfenvalerate, imidacloprid WG and SC, phosmet, and pyriproxyfen had sublethal effects which were reflected in the net reproductive rate and in the intrinsic rate of natural increase. In bioassay using adults, none of the individuals survived in the chlorpyrifos, lambda-cyhalothrin + chlorantraniliprole, lambda-cyhalothrin + thiamethoxam, malathion, or thiamethoxam treatments, and the azadirachtin, esfenvalerate, imidacloprid WG and SC, phosmet, and pyriproxyfen treatments were significantly lower compared to the control. None of the insecticides was harmless to first-instar larvae and adults of C. cubana under laboratory conditions showing their potential to reduce the efficiency of this predator.

Topics: Animals; Chlorpyrifos; Hemiptera; Insecticides; Larva; Limonins; Malathion; Neonicotinoids; Nitriles; Nitro Compounds; Pyrethrins; Pyridines; Random Allocation; Thiamethoxam; Toxicity Tests

Azalea lace bug, Stephanitis pyrioides (Scott) (Hemiptera: Tingidae) is a serious insect pest of azaleas (Rhododendron L. spp.) in the USA. S. pyrioides feeding causes chlorosis, which affects the aesthetic value and marketability of azalea plants. Management of S. pyrioides primarily involves neonicotinoid insecticides and their use has been drastically reduced or discontinued. Insect growth regulators (IGRs) are known to elicit transovarial activity as IGR-exposed adults produce non-viable eggs, which is not documented for S. pyrioides. Thus, transovarial activity of novaluron, azadirachtin, pyriproxyfen and buprofezin has been explored against S. pyrioides.. A low number of S. pyrioides young instars was produced when adults were exposed to topical novaluron compared with non-treated adults. When adults contacted dried residues of novaluron and buprofezin, production of young instars was reduced relative to non-treated controls. When insects exposed to 1.0× and < 1.0× doses of novaluron were compared, the number of young instars produced was similar.. Transovarial activity was elicited in S. pyrioides when adults were exposed to IGRs, especially novaluron. When adults were exposed to < 1.0× (up to 0.25×) and 1.0× doses of novaluron, the transovarial effect was similar. © 2019 Society of Chemical Industry.

Topics: Animals; Hemiptera; Insect Control; Insecticides; Juvenile Hormones; Limonins; Ovum; Phenylurea Compounds; Pyridines; Thiadiazines

Assessment of the susceptibility of natural enemies of pests to selective pesticides is relevant for a sustainable agriculture with low impact on the environment. The aim of this study was to assess the toxicity of two biorational insecticides, azadirachtin and pyriproxyfen in comparison to a neonicotinoid insecticide, acetamiprid, on pupae and adults of a Neotropical strain of Eretmocerus mundus. Adult emergence and survival were evaluated as lethal effects whereas the sublethal effects were assessed through the reproductive capacity, sex ratio, and longevity of the surviving first progeny. Adult emergence from treated pupae was reduced by all three insecticides, but azadirachtin at its maximum field recommended concentration (MFRC) proved the most toxic insecticide. The survival probability of emerged adults was reduced by the three insecticides below than 50% from 2 to 5 days after the adult emergence. Malformations in nonemerged adults from treated pupal hosts were observed at the MFRC of all three insecticides. Sublethal effects on survivors from pupal treatment could be evaluated at only the lowest azadirachtin concentration. At that concentration, though azadirachtin did not affect the reproductive capacity of females, the sex ratio and the longevity of the first progeny were disrupted. The survival of parasitoid adults after adult exposure was reduced by all three insecticides, pyriproxyfen at the MFRC being the most toxic. All insecticides at their half of MFRCs induced sublethal effects in the survivors' adults, with pyriproxyfen being the most harmful to the reproductive capacity of females. In conclusion, both biorational insecticides were toxic to E. mundus.

Topics: Animals; Female; Insecta; Insecticides; Limonins; Male; Neonicotinoids; Pupa; Pyridines

Interspecific variations in the susceptibility of freshly and embryonated eggs of Aedes albopictus, Ae. aegypti, Ae. atropalpus and Culex pipiens were tested against three classes of insect growth regulators (IGRs) including ecdysone agonist (azadirachtin), chitin synthesis inhibitor (diflubenzuron) and juvenile hormone analog (pyriproxyfen) at 0.001, 0.01, 0.1 and 1.0ppm concentrations. Egg hatching inhibition was dose dependent, the highest being at 1.0ppm concentration for freshly laid eggs of Ae. albopictus (pyriproxyfen: 80.6%, azadirachtin: 42.9% and diflubenzuron: 35.8%). Aedes aegypti showed lower egg hatching inhibition when exposed to pyriproxyfen (47.3%), azadirachtin (15.7%) and diflubenzuron (25.5%). Freshly laid eggs of Cx. pipiens were most susceptible to diflubenzuron. Aedes atropalpus eggs were tolerant to all three classes of IGRs. Embryonated eggs of Ae. albopictus, Ae. aegypti, Ae. atropalpus and Cx. pipiens were resistant to pyriproxyfen, azadirachtin and diflubenzuron than freshly laid eggs. The median desiccation time (DT50) of Ae. atropalpus eggs was maximum (5.1h) as compared to Ae. aegypti (4.9h), Ae. albopictus (3.9h) or Cx. pipiens (1.7h) eggs. Insignificant relationship between the rates of desiccation and egg hatching inhibition suggests other factors than physical providing eggs the ability to tolerate exposures to various IGRs. Egg hatching inhibition was due to the alteration in embryonic development caused by IGRs. Changes in the egg shell morphology and abnormal egg hatching from the side of the egg wall instead of operculum, was observed at higher concentrations of diflubenzuron. Morphological and physiological variations in eggs may be the key factor to influence the ovicidal efficacy of IGRs. The present data provide a base line for the improvement of the ovicidal efficacy of the insecticide and its formulation.

Topics: Aedes; Animals; Culex; Diflubenzuron; Juvenile Hormones; Limonins; Pyridines; Zygote

Pyriproxyfen, a juvenile hormone analogue, diflubenzuron, a chitin synthesis inhibitor, and azadirachtin, an ecdysone agonist, are three insect growth regulators (IGRs) considered as selective and effective insecticides for mosquitoes. Romanomermis iyengari (Welch) is a mosquito-parasitic mermithid that can provide biological control against many medically important mosquito species. The compatibility of these two control tactics was tested by evaluating the sublethal effects of exposure to IGR on nematode developmental stages (preparasitic, parasitic, and preparasitic + parasitic) using Culex pipiens larvae as the host. Sublethal concentrations of IGRs were 90 % emergence inhibition of host mosquito. Preparasitic exposure to pyriproxyfen, azadirachtin, and diflurbenzuron had no effect on infectivity, parasite load, sex ratio, or male size but reduced nematode female length and increased male sex ratio at one parasite/larva. When IGRs treatments were made against the parasitic and preparasitic + parasitic stages, pyriproxyfen and azadirachtin reduced R. iyengari infectivity, parasite load, and male nematode length, whereas pyriproxyfen exposure increased male sex ratio and reduced the female R. iyengari length. Thus, IGRs have significant negative impacts on different stages of mosquito mermithid that can destabilize the balance of host-parasite population interaction. Therefore, IGRs should be used with caution in mosquito habitats where these parasites have established.

Topics: Animals; Culex; Diflubenzuron; Female; Insecticides; Juvenile Hormones; Larva; Limonins; Male; Mermithoidea; Pyridines; Sex Distribution

An improved technique was developed to assay the toxicity of insecticides against aphids using an artificial diet. The susceptibility of the pea aphid Acyrthosiphon pisum (Harris) (Hemiptera: Aphidoidea) was determined for a selection of novel biorational insecticides, each representing a novel mode of action. Flonicamid, a novel systemic insecticide with selective activity as feeding blocker against sucking insects, showed high toxicity against first-instar A. pisum nymphs with an LC(50) of 20.4 microg/ml after 24 h, and of 0.24 microg/ml after 72 h. The toxicity was compared with another feeding blocker, pymetrozine, and the neonicotinoid, imidacloprid. In addition, four insect growth regulators were tested. The chitin synthesis inhibitor flufenoxuron, the juvenile hormone analogue pyriproxyfen, and the azadirachtin compound Neem Azal-T/S showed strong effects and reduced the aphid population by 50% after 3 days of treatment at a concentration of 7-9 microg/ml. The ecdysone agonist tested, halofenozide, was less potent. In conclusion, the improved aphid feeding apparatus can be useful as a miniature screening device for insecticides against different aphid pests. The present study demonstrated rapid and strong toxicity of flonicamid, and other biorational insecticides towards A. pisum.

Topics: Animals; Aphids; Diet; Feeding Behavior; Imidazoles; Insect Control; Insecticides; Juvenile Hormones; Lethal Dose 50; Limonins; Neonicotinoids; Niacinamide; Nitro Compounds; Nymph; Phenylurea Compounds; Pyridines; Triazines