Alabama: Summary of At-Plant Thrips Management Trials

    Defoliated cotton field ready for picking. Photo: Lance Clemmons, GW Farms.

    The Auburn Cotton Entomology team conducted several research trials in 2020 to help us continue to refine the “Cotton IPM System.” Below is a short summary of some our at-planting thrips management trials.

    We tested several insecticide seed treatments (IST) and in-furrow treatments at Prattville and Belle Mina. Overall, our treatments performed well and generally kept thrips injury below threshold. Moving into 2021, our recommendation is to either use an imidacloprid based IST (e.g. Gaucho, Aeris, Avicta Elite) or an in-furrow application of imidacloprid, acephate or aldicarb. One consideration for acephate is rain fastness. Even when soil applied at planting, excessive rainfall can leach acephate out of the rootzone and lead to less than ideal efficacy. Use the Thrips Model and scout fields to help determine when a foliar application may be necessary to supplement at-plant treatments.

    Figure below: Final thrips injury ratings (0-5 scale, 4th leaf) in at-plant seed and in-furrow insecticide trials in Prattville and Belle Mina, AL (2020). Letters indicate significant differences (P<0.05).

    Efficacy of Thrips Management Options for Reducing Damage and Preserving Cotton Yields, ACC#28

    Studies were conducted at the Prattville Agricultural Research Unit (PARU) in Prattville, AL and at the Tennessee Valley Research and Extension Center (TNVREC) in Belle Mina, AL, to evaluate selected seed and in-furrow treatments against thrips infesting seedling cotton.

    To evaluate treatments, whole plot thrips injury ratings were made on a 0-5 scale. On this scale, “0” means no injury is observed, “3” is considered the threshold when delays in maturity are likely and yield loss is possible, and “5” means thrips have killed all the plants in the plot. Although initial thrips injury ratings were higher at PARU, both locations had significant pressure at the final rating. Except for Cruiser and Orthene 97S at PARU, all treatments significantly reduced thrips injury ratings compared to the untreated controls (black seed, fungicide only).

    As has been consistently reported across the Mid-South and Southeast, Cruiser performed poorly at both locations, while Orthene performance was different at each location (see figure above). Although no significant differences in yield were observed among treatments, using a recommended at-plant insecticide yielded an average of ≈117 lbs of lint per acre compared to the untreated control (see figure below). These data show a consistent return on investment when using an at-plant insecticide to manage thrips in seedling cotton. Results from this study have also led to the removal of Cruiser from the AL Cotton IPM Guide recommendation for thrips management.

    Figure below: Impact of seedling thrips control during bloom

    Contact Scott Graham or Ron Smith for more information.

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