The influence of plant age on tolerance of rice to injury by the rice water weevil, Lissorhoptrus oryzophilus (Coleoptera: Curculionidae)

Abstract

For most plant species, tolerance to many types of herbivory increases as plants age, but the applicability of this pattern to root herbivory has not been tested. Injury to roots of rice plants by larvae of the rice water weevil, Lissorhoptrus oryzophilus Kuschel, causes severe reductions in yields in the United States. It is generally thought that young rice plants, because their root systems are smaller, are less tolerant than older plants of root feeding by L. oryzophilus. Field experiments were conducted to test this hypothesis. Plots of rice (4.7 to 6.5 m2) were established and subjected to natural infestations of L. oryzophilus larvae. A soil insecticide was applied to plots at different times during the tillering phase of rice in order to manipulate the timing of weevil infestation. The impact of these treatments (timings of insecticide applications) was assessed by comparing relationships between yield loss and larval pressure for each treatment using analysis of covariance. Yield losses ranged from 13% to over 40% in plots not treated with insecticide. Patterns of yield losses from plots treated with insecticide at different times were best explained by the hypothesis that yield loss is determined both by the age of plants infested and by the size of larvae infesting plants. Young plants appear to be less tolerant than older plants, and feeding by large larvae appears to be more deleterious than feeding by smaller larvae. Management practices that delay infestation of rice by L. oryzophilus until plants are older may be an important component of management programmes for this pest.

Impacts of Seeding Rate on Interactions Between Rice and Rice Water Weevils

“…Similar to the benefits of a delayed flood (Stout et al 2002a), a period of a shallow flooding may allow rice plants to escape heavy weevil pressure until plants are able to tolerate high numbers of weevils. A thorough examination of water use efficiency and an economic analysis will be necessary to determine costs associated with a shallow flood under large production systems.…”

“…Given the modest reduction in weevil numbers associated with shallow flooding and the non-significant increase in yield, it is clear that a shallow flood would not be a substitute for chemical control, but it may serve as a valuable component of an integrated pest management system. Other cultural practices that could be used in conjunction with a shallow flood include: avoiding planting at low seeding rates (Thompson and Quisenberry 1995;Stout et al 2009), delaying the permanent flood to allow plants to develop a robust root system and become more tolerant to L. oryzophilus injury (Stout et al 2002a), selecting a planting date appropriate to the area Espino et al 2009;Stout et al 2011), and choosing a variety that is more tolerant to weevil injury Rice et al 1999;Stout et al 2001;Bernhardt and Richards 2003;Tindall et al 2004). A shallow flood is more likely to be beneficial in areas that have historically low infestation levels.…”

“…However, draining is not recommended, because rainfall can prevent the soil from drying sufficiently, and additional input costs are associated with draining (Hesler et al 1992;Quisenberry et al 1992;Thompson et al 1994). Manipulating water such that plants are older when floods are established can aid in reduction of L. oryzophilus damage because older plants are better able to tolerate injury from weevil larvae than younger plants (Stout et al 2002a) and are less preferred for oviposition (Bang and Tugwell 1976). Delayed flood can be accomplished by adopting drillseeding practices instead of water-seeding rice, or delaying flooding in water-seeded rice from the 2-3 leaf stage to the 4-5 leaf stage (Rice et al 1999;Zou et al 2004;Bernhardt 2006).…”

Induced Jasmonate Signaling Leads to Contrasting Effects on Root Damage and Herbivore Performance

“…Whereas light and temperature vary profoundly above ground, humidity levels vary dramatically in soils between locations and over the growing season (Eagleson, 1978;Stout et al, 2002). Both plants and herbivores have adapted to flooded and nonflooded conditions (Saito et al, 2005;Voesenek and Bailey-Serres, 2013), and the interaction between abiotic and biotic factors may determine the outcome of their interaction (Erb and Lu, 2013).…”

Effects of belowground herbivory on the survival and biomass of Lolium perenne and Plantago lanceolata plants at various growth stages

“…When the plant is small, the loss of tissues due to herbivory can cause mortality (Moles and Westoby 2004;Fenner and Thompson 2005;Hanley and May 2006;Hanley and Sykes 2009). Stout et al (2002) evaluated the tolerance of rice plants at different growth stages to the belowground herbivore, Lissorhoptrus oryzophilus Kuschel. To date, and to our knowledge, this is the only other study on the tolerance of different stages of plants to belowground herbivory.…”