Adding organic matter does not increase seedcorn maggot (Delia platura Meigen) damage to crop seeds

Seedcorn maggot (SCM) (Delia platura Meigen) is an early-season generalist pest to many economically important crops. This pest has been prophylactically managed with neonicotinoid-coated seeds. However, this form of protection will not be available in NYS after 2029. Concerns have been raised that adding plant residues or animal manure to fields for fertilization will increase SCM damage to seeds. Nonetheless, few studies have experimentally tested this. We collected data in 2023 and 2024 to answer the following questions: (1) Does the addition of plant or animal residues increase SCM damage? (2) Does seed damage by SCM vary between different types of manure and crop types? In 2023, we collected seeds from untreated agricultural plots and plots treated with liquid dairy manure, silage alfalfa, or a fertilizer spray. In 2024, we collected seeds from untreated plots and plots treated with an NPK fertilizer, liquid dairy manure, or bedded manure. We planted and sampled from strips of corn and soybean in each treatment. We found no difference in the number of SCM larvae found between the treatments in 2023 or 2024. In 2024, seeds in untreated plots had less damage than seeds in plots treated with a fertilizer spray. Interestingly, crop type affected seed damage and SCM abundance regardless of soil amendment. Our results suggest that SCM preference is determined more by the crop type than by the amendments applied, suggesting that the use of manure and plant residues could still be a viable management practice once neonicotinoids are no longer available.