Tolerance to rice water weevil, Lissorhoptrus oryzophilus Kuschel (Coleoptera: Curculionidae), infestations among hybrid and inbred rice cultivars in the Southern U.S.

Abstract

The rice water weevil, Lissorhoptrus oryzophilus Kuschel, is the most destructive insect pest of rice in the U.S. This insect poses a global threat to rice production, having invaded rice-producing regions of Asia and Europe. Tolerance is a type of plant resistance that allows crop plants to maintain yield in spite of injury by herbivores. This study was conducted to test the hypothesis that tolerance to L. oryzophilus infestations differs between hybrid and inbred rice cultivars. Field experiments were conducted in Louisiana in 2016–2017 and in multiple locations (Texas, Mississippi, and Louisiana) in 2018. Plant tolerance was assessed by evaluating L. oryzophilus infestations and yields from insecticide-protected and unprotected plots of hybrid and inbred rice cultivars. Infestations of L. oryzophilus negatively affected rice yields, with losses across cultivars ranging from 16.4 to 48.0% in 2016 and 4.2–29.2% in 2017. In the multiple location experiment in 2018, yield losses ranged from 4.1 to 29.7, 7.7–17.2, and 4.5–12.2% in Louisiana, Texas, and Mississippi, respectively. Comparisons of yields between insecticide-protected and unprotected plots indicated that hybrid cultivars exhibited higher tolerance to L. oryzophilus infestations than inbred cultivars in 2016 and 2017. Moreover, in the multiple location experiment in 2018, yield losses were lower in hybrid compared to inbred cultivars in Texas, but no differences in yield losses across cultivars were observed in Louisiana and Mississippi. Rice cultivars expressing tolerance to L. oryzophilus could be used to reduce pest damage in situations where use of insecticides is not practical, too expensive, or only partially effective.