Safety Evaluation Of Mancozeb On Harmonia Axyridis

Mancozeb is a broad-spectrum multilocus fungicide that is widely used to control crop diseases caused by various fungi.However,its metabolite Ethylene thiourea(ETU)has "three-cause" toxicity,and in recent years,ecological security problems caused by mancozeb have been increasing.Harmonia axyridis is a predatory natural enemy of common pests in agricultural and forestry production,With the vigorous implementation of the Integrated Pest Management(IPM)concept,the commercial application scope of H.axyridis involves a variety of mancozeb registered crops,and there is also a temporal and spatial overlap between the release of H.axyridis and the use of mancozeb in agricultural production.Therefore,it is urgent to clarify the influence of mancozeb on H.axyridis,so as to better protect and utilize natural enemies insects and guide the release timing and release of H.axyridis.In order to better coordinate the compatibility of chemical control and biological control,it can provide a theoretical basis for the development of efficient and sustainable IPM plans.1.Effect of mancozeb on the developmental of H.axyridisThe three concentrations of mancozeb caused developmental retardation in the larvae of H.axyridis,prolonged the development period of second-instar larvae,third-instar larvae and pupal stage,and reduced the fresh weight of pupal and first adult infants.In addition,depending on the stage of initial feeding on venomous aphids,H.axyridis larvae and adults show different sensitivities to mancozeb.Among them,the continuous ingestion of poisonous aphids treated with different concentrations of mancozeb at the larval stage had no significant effect on the feathering rate,but reduced the larval survival rate and pupation rate of H.axyridis.Only continuous ingestion of poisonous aphids in the adult stage had no significant effect on the lifespan and survival rate of female adult worms.2.Effect of mancozeb on the predation ability of H.axyridisAfter continuous ingestion of venom aphids by the first hatching larvae,mancozeb reduced the predation of second-instar larvae in a dose-dependent manner,and 800 mg/L and 1600 mg/L mancozeb also reduced the predation of fourth-instar larvae.During the continuous ingestion of venominous aphids for 10 days,there was no significant difference in the daily intake of venom aphids of different concentrations of venom aphids.On day 10 of the feeding of venom aphids by only the newly emerged,the effect of mancozeb on the predation ability of female adults was also studied.The results showed that the predation function response of female adults of H.axyridis to aphids was still Holling II.,but the predation function response parameters changed.The treatment time of pea aphids was prolonged,the theoretical maximum feed intake decreased,and the instantaneous attack rate increased but had little effect on the search effect.3.Effect of mancozeb on the reproductive of H.axyridisMancozeb had weak reproductive toxicity against female adults of H.axyridis at two different stages of feeding on poisonous aphids.Mancozeb has a certain inhibitory effect on the reproductive development of female adults of H.axyridis,and also reduces fecundity to varying degrees.The inhibition of reproductive development was manifested by different degrees of inhibition of Vg1,Vg2 and Vg R expression levels of genes related to ovarian development,a decrease in the proportion of V-level mature ovarian development,and a decrease in ovarian development index.There were also differences in the effects of different concentrations of mancozeb on the fecundity of H.axyridis at two different feeding stages.Among them,after continuous ingestion of different concentrations of venominous aphids from the first hatching larvae,the three concentrations of mancozeb reduced the total egg production of H.axyridis for 20 days,but had no significant effect on egg hatchability and pre-spawning of female adults.In contrast,the continuous ingestion of pea aphids treated with mancozeb in newly emerged alone had no significant effect on the total egg production at 20 days,but 800 mg/L and2400 mg/L mancozeb significantly reduced egg hatchability,and 2400 mg/L mancozeb significantly prolonged the pre-spawning stage of female adults of H.axyridis.4.Effect of mancozeb on the detoxification immunity of H.axyridisMancozeb affects transcription levels of genes associated with detoxification immunity in H.axyridis.In addition,only the initial female adult worms continued to ingest the poisonous aphids treated with mancozeb,which also caused oxidative stress damage.It is manifested by the accumulation of malondialdehyde(MDA),a lipid peroxidation product in vivo,which inhibits the activity of superoxide dismutase(SOD)and the activity of catalase(CAT),and also reduces the content of the non-enzymatic antioxidant glutathione(GSH).In addition,it also induces an increase in the activity of the insect detoxification enzyme acetylcholinesterase(Ach E).In conclusion,the results of this study showed that long-term exposure to three concentrations of mancozeb related to the recommended dose in the field all had certain negative effects on H.axyridis,and there were different degrees of manifestation in two different feeding stages.Therefore,it is recommended to try to avoid the simultaneous use of mancozeb and H.axyridis.