The value of insecticidal seed treatments for US rice farmers

Abstract The rice water weevil, Lissorhoptrus oryzophilus (Coleoptera: Curculionidae), has been the primary economic pest of rice, Oryza sativa, in the United States for more than 100 yr. Management of L. oryzophilus with conventional foliar insecticides is challenging owing to the difficulty in effectively timing insecticide applications against adults as well as the subterranean, aquatic feeding of larvae on rice plant roots. Two neonicotinoids (thiamethoxam and clothianidin) and 2 diamide (chlorantraniliprole and cyantraniliprole) seed treatments have replaced foliar applications against L. oryzophilus and other pests in the past 2 decades. The neonicotinoids control L. oryzophilus along with more sporadic pests including chinch bugs (Hemiptera: Blissidae), Colaspis spp. (Coleoptera: Chrysomelidae), and aphids. The diamides have superior activity against L. oryzophilus and provide control of several lepidopteran pests including 3 Crambid stem borers (Eoreuma loftini, Diatraea saccharalis, and Chilo plejadellus) and fall armyworm, Spodoptera frugiperda (Lepidoptera: Noctuidae). The products used individually or in combination have greatly improved control of L. oryzophilus and other insect pests providing immense value to US rice producers. Currently, the products are used on approximately 80% of rice acreage in Arkansas, Louisiana, Mississippi, Missouri, and Texas. Diamides are predominant in Louisiana and Texas, while neonicotinoids are most prevalent in Arkansas, Mississippi, and Missouri. Across the region, the insecticidal seed treatments were used on 775,000 ha at a total cost of 19 million USD. Estimated return on investment from pest losses prevented range from 100 to 500 USD per ha, making the total economic value of insecticidal seed treatments in US rice approximately 77.5 to 387.5 million USD annually. Future rice pest management strategies should aim to diversify tactics to mitigate resistance development and preserve efficacy of these valuable seed treatments.