Suppression of the Sugarcane Aphid, Melanaphis sacchari (Hemiptera: Aphididae), by Resident Natural Enemies on Susceptible and Resistant Sorghum Hybrids

Abstract

The sugarcane aphid, Melanaphis sacchari (Zehntner) (Hemiptera: Aphididae), is an invasive sorghum pest that has threatened over 90% of North American sorghum production. Resident parasitoids, coccinellids, syrphids, and lacewings prey on this aphid. Our objective was to compare and estimate parasitoid and predator suppression of sugarcane aphids placed on resistant and susceptible hybrids in a field setting using natural enemy exclusion cages. During 2018 and 2019 along the Texas Gulf Coast and Central Oklahoma, three natural enemy exclusion treatments—no exclusion (full access for parasitoids and predators), partial exclusion (access limited to parasitoids), and complete exclusion (excludes parasitoids and predators)—were used. The parasitoid Aphelinus nigritus Howard (Hymenoptera: Aphelinidae) accounted for 90% of recovered natural enemies. In 2018, aphid suppression attributable to A. nigritus was ca. 95% on the resistant hybrids and 80% on the susceptible hybrids when comparing aphid counts from complete and partial exclusion treatments, while few predators were observed. In 2019, aphid suppression was attributed to a combination of predation and parasitism. Relatively more predators were recorded at both sites, accounting for 14% to 33% of specimens recovered in the no exclusion treatment. Aphid suppression attributed to predators and parasitoids ranged from 85% on aphid-resistant hybrids and 27% on susceptible hybrids in south Texas and >95% on both hybrids in Oklahoma when comparing aphid abundance in the complete and no exclusion treatments. Parasitism and predation contributed to aphid regulation on both hybrids, which may accrue multiple benefits leading to a more resilient sugarcane aphid management system.

Parasitoids and Predators of the Invasive Aphid Melanaphis sorghi Found in Sorghum and Non-Crop Vegetation of the Sorghum Agroecosystem

“…The vegetative types of this study are relevant components of the sorghum agroecosystem and were found to harbor natural enemies of M. sorghi in- and off-season to varying degrees, depending on the natural enemy taxa. Apehlinus nigritus abundance across time and the three vegetation types bodes well for it to have a top-down suppression influence on M. sorghi and is consistent with previous information on its response of M. sorghi on sorghum [ 8 , 11 , 26 , 27 ]. We conclude that the natural enemy species composition and seasonal variation in abundance across vegetation types may be useful indicators of top-down regulatory potential for M. sorghi .…”

“…Its abundance across the three vegetation types and its representation in-season and off-season bodes well for its function as a key suppression agent for M. sorghi . Aphelinus nigritus has been found consistently from south to central Texas on both susceptible and aphid-resistant sorghum [ 11 , 26 , 27 ]. Aphelinus sp.…”

“…It is the dominant parasitoid of greenbug on wheat in the Great Plains in Oklahoma and has also been detected preying on other cereal aphids in the Great Plains [ 18 , 32 ]. It has been detected preying on sugarcane aphid in Mexico [ 9 , 10 , 27 , 28 ]; however, its abundance in south Texas has been variable over the last several years (A.M.F., M.J.B. personal observation).…”

Quantifying the impacts of symbiotic interactions between two invasive species: the tawny crazy ant (Nylanderia fulva) tending the sorghum aphid (Melanaphis sorghi)

“…In these instances, interactions between two invasive pests ecologically facilitated aphid fitness and reduced crop health. Currently in the US, the composition of sorghum aphid natural enemies and ability to control aphids has been reported ( Hewlett, Szczepaniec & Eubanks, 2019 ; Maxson et al, 2019 ; Elliott et al, 2021 ; Faris, Brewer & Elliott, 2022 ; Faris, Elliott & Brewer, 2022 ) along with the finding that RIFA did not negatively impact the presence of natural enemies that parasitize sorghum aphids feeding on sorghum ( Wright, 2021 ). However, additional assessments of ant-sorghum aphid dynamics is needed, which could include identifying other ant species that are likely to increase aphid biomass or assessing the impact of ant presence on natural enemies in different ecosystems.…”

Alterations in Ferrisia gilli (Hemiptera: Pseudococcidae) phenology in California pistachios and potential impacts on controls

“…The spray timing in late May was based on an economic threshold of 1 mealybug per 6–13 nut clusters, depending on expected yield, which led to adequate control (Haviland et al 2015). While the current F. gilli pest management program is based solely on insecticide applications, resident natural enemies of an insect pest can support population suppression (e.g., Faris et al 2022). Ferrisia gilli is attacked by several natural enemy species; however, parasitoids have only been reported in almonds and grapes (Haviland et al 2012, Wunderlich et al 2013), and not in pistachios.…”