Entomopathogenic Nematodes Combined with Adjuvants Presents a New Potential Biological Control Method for Managing the Wheat Stem Sawfly, Cephus cinctus (Hymenoptera: Cephidae)

Abstract

The wheat stem sawfly, (Cephus cinctus Norton) Hymenoptera: Cephidae, has been a major pest of winter wheat and barley in the northern Great Plains for more than 100 years. The insect’s cryptic nature and lack of safe chemical control options make the wheat stem sawfly (WSS) difficult to manage; thus, biological control offers the best hope for sustainable management of WSS. Entomopathogenic nematodes (EPNs) have been used successfully against other above-ground insect pests, and adding adjuvants to sprays containing EPNs has been shown to improve their effectiveness. We tested the hypothesis that adding chemical adjuvants to sprays containing EPNs will increase the ability of EPNs to enter wheat stems and kill diapausing WSS larvae. This is the first study to test the ability of EPNs to infect the WSS, C. cinctus, and test EPNs combined with adjuvants against C. cinctus in both the laboratory and the field. Infection assays showed that three different species of EPNs caused 60–100% mortality to WSS larvae. Adding Penterra, Silwet L-77, Sunspray 11N, or Syl-Tac to solutions containing EPNs resulted in higher WSS mortality than solutions made with water alone. Field tests showed that sprays containing S. feltiae added to 0.1% Penterra increased WSS mortality up to 29.1%. These results indicate a novel control method for WSS, and represent a significant advancement in the biological control of this persistent insect pest.

Field efficacy of insect pathogen, botanical, and jasmonic acid for the management of wheat midge Sitodiplosis mosellana and the impact on adult parasitoid Macroglenes penetrans populations in spring wheat

“…IPNs have been most successfully used against different soil inhabiting insect pest species (Kaya & Gaugler, 1993). However, with the development of a suitable adjuvant (Barricade polymer gel) that can protect infective juveniles from ultraviolet rays or extend their survival on aboveground foliage Shapiro-Ilan et al, 2016); IPNs can now be considered for use against aboveground crop insect pests as well Portman et al, 2016;Shapiro-Ilan et al, 2016). Among the several nematode species, S. feltiae has been recognized to have many advantages including a broad host range, high virulence, adaptability to a wide range of temperatures (10-30°C) and an ability to seek their target host (Gaugler et al, 1989).…”

“…Among the several nematode species, S. feltiae has been recognized to have many advantages including a broad host range, high virulence, adaptability to a wide range of temperatures (10-30°C) and an ability to seek their target host (Gaugler et al, 1989). Furthermore, in Montana, S. feltiae has recently been found to be the most effective nematode species against a wide range of important foliar insect pests including wheat stem sawflies and flea beetles when applied in conjunction with 1% Barricade under field conditions Portman et al, 2016). Thus, our findings and those of these previous field studies indicate that S. feltiae has the potential to be used against several foliar insect pests in Montana and can be combined with many IPM programs.…”

“…However, for JA and Scanmask preparations, 1 mg JA was dissolved in 1 mL acetone and then dispersed in water to give a solution of 1 mL JA per liter of water (El‐Wakeil et al ., ), while 1% Barricade polymer gel (Barricade International, Inc., FL, USA) was added to mixture of Scanmask and tap water (Table ). This percentage of gel mixed with nematode S. feltiae improved control of other foliar insect pests such as: wheat stem sawflies Cephus cinctus Norton (Hymenoptera: Cephidae) and flea beetles Phyllotreta cruciferae Goeze (Coleoptera, Chrysomelidae) (Antwi & Reddy, ; Portman et al ., ). Two controls were included in the study.…”

“…All biopesticide products were thoroughly mixed with tap water to obtain the desired concentrations (Table 1). However, for JA and Scanmask preparations, 1 mg JA was dissolved in 1 mL acetone and then dispersed in water to give a solution of 1 mL JA per liter of water (El-Wakeil et al, 2010), while 1% Barricade polymer gel (Barricade Portman et al, 2016). Two controls were included in the study.…”

“…Nematode infective juveniles (IJs) enter insect hosts through natural openings (mouth, spiracles and anus), penetrate into the hemocoel and then release symbiotic bacteria that will kill the hosts within 2 d (Grewal et al, 2006). Insect pathogens have been successfully examined or used against a variety of insect pest species and considered as components of an IPM program (Chandler et al, 2011;Shrestha et al, 2015;Portman et al, 2016;Shapiro-Ilan et al, 2016). However, the effect of insect pathogens on S. mosellana has received little attention, except for the study by Keller and Wilding (1985), reporting that naturally occurring fungus Entomophthora brevinucleate Nov. (Zygomycota: Entomophthorales) was pathogenic to adults in winter wheat fields in Switzerland.…”