Influence of Host-Plant Surface Chemicals on the Oviposition of the Cereal Stemborer Busseola Fusca

Abstract

The chemical composition of plant surfaces plays a role in selection of host plants by herbivorous insects. Once the insect reaches the plant, these cues determine host acceptance. Laboratory studies have shown that the stem borer Busseola fusca (Lepidoptera: Noctuidae), an important pest of sorghum and maize in sub-Saharan Africa, is able to differentiate between host and non-host plant species. However, no information is available on the cues used by this insect to seek and accept the host plant. Thus, the role of surface phytochemical stimuli on host selection and oviposition by B. fusca was studied in the laboratory using two host plants, sorghum, Sorghum bicolor, and maize, Zea mays, and one non-host plant, Napier grass, Pennisetum purpureum. The numbers of eggs and egg masses deposited on the three plant species were compared first under no-choice and choice conditions. In both cases, more eggs and egg masses were laid on maize and sorghum than on the non-host. Artificial surrogate stems treated with a water or chloroform surface extract of each plant were then compared with surrogate stems treated with, respectively, water or chloroform as controls, under similar conditions. Surrogate stems treated with plant water extracts did not show an increase in oviposition when compared to controls, indicating that the major compounds in these extracts, i.e., simple sugars and free amino acids, are not significantly responsible for the oviposition preference. By contrast, a chloroform extract of sorghum enhanced oviposition on the surrogate stems compared to the control, while those of maize and Napier grass showed no significant effects. Analysis of the chloroform extract of sorghum showed higher amounts of α-amyrin, ß-amyrin, and n-nonacosane compared to those of maize and Napier grass. A blend of the three chemicals significantly increased oviposition compared to the chloroform-treated control, indicating that these compounds are part of the surface chemical signature of the plant responsible for host recognition and oviposition by B. fusca.

Performance of Sesamia nonagrioides on cultivated and wild host plants: Implications for Bt maize resistance management

“…Sugars and amino acids detected by chemoreceptors have been reported to play a major role in discrimination between plants for oviposition in some lepidopteran species 21,62,63 . However, results are inconclusive when it comes to noctuid species 22,64 . Our study does not reveal an oviposition preference of S. nonagrioides for any of the plants based on their free sugars content, since, even though no differences in this parameter were found between maize and sorghum leaves, adults laid significantly more eggs on maize.…”

“…To evaluate whether alternative hosts could be useful in insect resistance management (IRM) plans it is key to evaluate the performance of this noctuid pest on these plant species, as well as its preference between them and its main host, maize, to learn whether large and healthy populations of the pest could build up in the alternative hosts. In this context, determining the free amino acid and soluble sugars content in the tested plant species could provide important information, since these parameters have been reported to influence oviposition preference and to stimulate larval feeding in a range of insect species, including noctuids 21,22 …”

Preference of Bt‐resistant and susceptible Busseola fusca moths and larvae for Bt and non‐Bt maize

“…Host plant selection by B. fusca, for example, is influenced by plant species and developmental stage (Van Rensburg et al, 1987, 1989. Moths utilize plant chemical cues (Khan et al, 2000;Chamberlain et al, 2006;Juma et al, 2016) and physical attributes such as surface texture and stem diameter to locate and recognise preferred host plants (Van Rensburg et al, 1989;Calatayud et al, 2008a). The physical and chemical attributes of plants that mediate host selection may be altered in genetically engineered cultivars compared to their isogenic counterparts (Turlings et al, 2005;Han et al, 2016).…”

Draft Genome of Busseola fusca, the Maize Stalk Borer, a Major Crop Pest in Sub-Saharan Africa

“…2015). Because B. fusca have been shown to utilize chemical cues when searching for oviposition sites (Juma et al. 2016), future work should look at the importance of these unique sequences in intraspecific communication and selection of suitable egg-laying sites in B. fusca as a part of a comprehensive pest management strategy.…”