Seed treatment for managing fall armyworm as a defoliator and cutworm on maize: plant protection, residuality, and the insect life history

Abstract

BACKGROUND: The highly polyphagous and invasive fall armyworm (FAW, Spodoptera frugiperda) can feed on different plant parts of host crops, damaging whorls and stalks in early maize growth stages. Systemic insecticide seed treatment (IST) could minimize this damage, although the residual efficacy may vary with the plant tissue damaged. Using damage rating scales and artificial infestation in controlled conditions, we determined the potential of IST against FAW attacking maize whorl leaves or the stalk base.RESULTS: Chlorantraniliprole, cyantraniliprole, or thiodicarb + imidacloprid IST similarly killed > 80% FAWs for 1 or 2 weeks after plant emergence depending on the plant tissue attacked. The residual efficacy (i.e. time after plant emergence sustaining > 80% larval mortality) lasted from the first to the eleventh day (VE-V3 maize growth stages), while for cutworm on the maize stalk base, it lasted 3-7 days after plant emergence (V1-V2 stages). In terms of damage, the ISTs lasted 15 days after emergence (V4 stage) for FAW on whorl leaves and 10 days (V3 stage) for FAW feeding on the stalk base. The larvae surviving on the seedtreated plants underwent sublethal effects in growth and development, reducing insect fitness.CONCLUSION: Diamide or carbamate + neonicotinoid seed treatments kill FAW larvae on maize whorls or stalks in favorable edaphoclimatic and insecticide-susceptibility conditions. The cumulative impacts of systemic IST on aboveground insect pests go beyond mortality. The ISTs studied can be valuable against FAW in maize, for instance, to help protect varieties that may not express sufficient insect resistance in maize early growth stages.

Insecticide seed treatment against corn leafhopper: helping protect grain yield in critical plant growth stages

“…In the VE–V4 maize growth stages, seed treatment with neonicotinoids reduced the severity of stunt disease, plant mortality, and maize yield loss. The seed treatment did not change the plant phenotype and performance, indicating no endpoint phytotoxicity in plant growth and yield in the non‐infested control plants 59–63 . Therefore, seed treatment can help protect the early maize growth stages, from emergence to V4; however, this protection is unlikely to be observed after this period, as indicated in both the greenhouse and field.…”

“…Therefore, seed treatment can help protect the early maize growth stages, from emergence to V4; however, this protection is unlikely to be observed after this period, as indicated in both the greenhouse and field. The residual period of seed treatment is generally less than three weeks, coinciding with the V2–V4 maize growth stages 61,62 . Plant protection was likely due to the insecticidal effects of clothianidin and imidacloprid.…”

“…The seed treatment did not change the plant phenotype and performance, indicating no endpoint phytotoxicity in plant growth and yield in the non-infested control plants. [59][60][61][62][63] Therefore, seed treatment can help protect the early maize growth stages, from emergence to V4; however, this protection is unlikely to be observed after this period, as indicated in both the greenhouse and field. The residual period of seed treatment is generally less than three weeks, coinciding with the V2-V4 maize growth stages.…”

“…The residual period of seed treatment is generally less than three weeks, coinciding with the V2-V4 maize growth stages. 61,62 Plant protection was likely due to the insecticidal effects of clothianidin and imidacloprid. These can be absorbed and translocated in the plant, causing mortality of the corn leafhopper and green belly stinkbug [Diceraeus (Dichelops) melacanthus, Hemiptera: Pentatomidae] in early maize growth stages.…”

“…[34][35][36]62,63 Our results provide fundamental support for integrating seed treatment with other pest management measures against the corn stunt disease complex to protect the most susceptible maize growth stages. 50,61 The seed treatment could interact with other pest control measures and soil organisms, which is deserving of more research. 64 The physicochemical properties of neonicotinoids (i.e.…”