Crop-specific mortality of southern green stink bug eggs in Bt- and non-Bt cotton, soybean and peanut

Abstract

Increasing insecticide use against stink bugs erodes benefits accrued to cotton production in the southeastern USA by eradication of the boll weevil and widespread use of Bt-transgenic cotton. Biological control programs designed to mitigate the impact of these pests would be beneficial; therefore, we sought to identify and assess naturally occurring biological control agents of stink bug eggs in cotton, peanut and soybeans, three important crops and stink bug hosts in the region. Two studies were conducted utilising digital imaging of sentinel egg masses to capture enemies present and sequential imaging over time to characterise the type and amount of damage inflicted on the egg masses. The first study utilised plots of soybean, Bt cotton, non-Bt cotton and peanut. The second study focused on ant predation in cotton by excluding fire ants from half of the plots. Sentinel egg masses of the southern green stink bug were placed in all plots at weekly intervals and were photographed at placement and at intervals over 72 h. Surviving egg masses were collected and held in the laboratory to assess parasitism in the first study. Predation of eggs was high in peanut (74Á86%) and soybean (39Á65%), and lower in Bt (26Á34%) and non-Bt (4Á21%) cotton over the two years. Parasitism was low overall (0.17Á19.0%). Most egg predation in cotton and peanut was attributable to fire ants, whereas long-horned grasshoppers dominated in soybean. Exclusion of fire ants in cotton significantly reduced egg mortality, indicating their predominance as mortality agents in cotton.

Competitive release and outbreaks of non‐target pests associated with transgenic Bt cotton

“…While competitive release and insecticide release are both important drivers of stink bug outbreaks in Bt cotton, other processes should also be considered. Stink bugs are not controlled by natural enemies in southeastern cotton fields (Jones et al 1996, Olson andRuberson 2012), so the absence of effective natural enemies probably also contributes to the stink bug outbreaks. Finally, it is possible that the landscape structure has favored the outbreaks of these polyphagous stinkbugs; in the southeastern USA, maize and soybean are common alternative hosts, on which stink bugs can reproduce and build up populations before cotton becomes a suitable host (Toews and Shurley 2009).…”

A review of the sentinel prey method as a way of quantifying invertebrate predation under field conditions

“…The majority (n = 35) of the sentinel prey were secured onto various substrates (cardboard, wax paper, plastic, mesh cloth). Prey was also secured using pins (Naranjo, 2005;Hong et al, 2011;Lundgren & Fergen, 2011;Mathews et al, 2011;Dobbs & Potter, 2014), staples (Wilson et al, 2004;Weber et al, 2008;Olson & Ruberson, 2012), thread or wire (Lövei & Brown, 1993;Ehler, 2002Ehler, , 2004Ehler, , 2007Mathews et al, 2004;Takeuchi & Watanabe, 2006). In 3 studies (Lövei & Brown, 1993;Naranjo, 2005;Hong et al, 2011), prey was placed on the soil surface unsecured.…”

“…Real prey has mostly been used to evaluate the impact of a particular predator/parasitoid, including the ants Pheidole megacephala (Jones et al, 2001), and Solenopsis invicta (Diaz et al, 2004;Olson & Ruberson, 2012), the encyrtid wasp Oobius agrili, a parasitoid of the invasive emerald ash borer (Agrilus planipennis) (Duan et al, 2011), the egg parasitoid Trichogramma brassicae (Burgio & Maini, 1995), the pupal parasites of Musca domestica (Mullens et al, 1986), and telenominaeid parasitoids of Euschistus heros (Vieira et al, 2014). The importance of predation and parasitism on a specific prey, usually a pest, was studied on the lepidopteran pests Cydia pomonella (Libourel & Franck, 2012), Spodoptora exigua (Ehler, 2004;2007), and Udea stellata (Kaufman & Wright, 2009), as well as the stink bugs Euschistus servus (Tillman, 2010), and Nezara viridula (Ehler, 2002;Tillman, 2010).…”

“…Nonharvested plots boost predation which decreases with distance from such areas (Hossain et al, 2012), and fertilization in cotton reduces predation but not parasitism (Chen & Ruberson, 2008). A study in transgenic Bt and non-Bt cotton found no difference in predation on eggs and pupae of Pectinophora gossypiella (Naranjo, 2005), but predation on Nezara viridula eggs is higher in Bt-than non-Bt cotton (Olson & Ruberson, 2012).…”

The Good Side of the Bad Guys: Predation of Lepidopteran Pests by Solenopsis invicta Buren (Hymenoptera: Formicidae) in the Florida Panhandle

“…The potential pest predation by S. invicta has been reported in several agroecosystems. According to Olson and Ruberson (2012), the most important predator of stink bug eggs in cotton was S. invicta. A field study in corn (Knutson & Campos 2008) provided evidence that S. invicta greatly reduced pre-pupa of H. zea when getting ready for pupation on the ground, although this ant was not effective in reducing the population of larvae and eggs within the corn canopy.…”