Can climate-driven change influence silicon assimilation by cereals and hence the distribution of lepidopteran stem borers in East Africa?

• For three East African mountains, Si concentrations in soil and maize decreased with altitude.
• Low temperatures at high altitudes negatively affected Si assimilation by maize.
• Between the two main maize pests in East Africa mountains, Busseola fusca was more susceptible to Si than Chilo partellus.
• Si partly explains the predominance of B. fusca in the highlands and of C. partellus in the lowlands.
• Climate change should modify the Si level in plants and as a results the distribution and abundance of maize pests.

In East Africa, lepidopteran stemborers such as Chilo partellus and Busseola fusca are major constraints to production of maize, which is the main staple food crop in the region. Cereals depend on silicon (Si)-based defences to fight off herbivores. Using altitudinal ranges in the East African highlands as ecological surrogates for inferring climate change, it was shown that Si concentrations in soil and maize decreased with altitude. This was attributed, in part, to low temperatures at high altitudes, which negatively affected Si assimilation by maize. Experiments showed that B. fusca was more susceptible to Si than C. partellus. Hence the predominance of B. fusca in the highlands and of C. partellus in the lowlands could be partly explained by altitudinal differences in Si concentrations in maize plants. Therefore, a rise in temperature due to climate change should enhance the plants’ Si assimilation and as a result C. partellus might move into the higher altitudes and increasingly displace B. fusca.

Figure optionsDownload as PowerPoint slide