One of the biggest challenges currently facing grain producers in South Africa is the occurrence of grain aphids in wheat-growing regions and the development of resistance to certain insecticide groups. Three grain aphid species, the Russian grain aphid (RGA) (Diuraphis noxia), the oat aphid (Rhopalosiphum padi), and the rose grain aphid (Metopolophium dirhodium), are currently the main threat to grain farmers across the country.
A knockout blow for grain aphids
Currently, grain aphids are mainly controlled in two ways: by chemical agents and through the use of genetically resistant cultivars. Although these methods were initially effective, aphids are extremely adaptable and develop resistance over time under selective pressure. This has led to the emergence of large, rapidly spreading populations.
In a recent article in Wheat Focus, Dr. Astrid Jankielsohn of the ARC-Small Grain Institute highlights the phenomenon in winter rainfall and irrigation areas where the development of resistance to some of the most common chemical pesticides is observed. Currently, there are a limited number of active ingredients registered for use on grain aphids: namely, the organophosphates (Group 1 B), the neonicotinoid group (Group 4 A) and the butenolide group (Group 4 D). In the past, insecticides in Group 1 B and Group 4 A were mainly used. The repeated use of the active ingredients in these groups, especially dimethoate, imidacloprid, acetamiprid and thiamethoxam, has resulted in the susceptibility of grain aphids decreasing, and consequently, the effectiveness of the active ingredients has diminished, posing a serious production risk for farmers.
(Insert table below)
Table 1. Active ingredients registered against grain aphids on wheat in South Africa
Active ingredient |
Pesticide group |
IRAC Group code |
Dimethoate |
Organophosphates |
1B |
Imidacloprid |
Neonicotinoids |
4A |
Acetamiprid |
Neonicotinoids |
4A |
Thiamethoxam |
Neonicotinoids |
4A |
Flupyradifurone |
Butanolides |
4D |
With this challenge in mind, Bayer has developed an effective systemic product against oat aphids, Russian wheat aphids, and other aphid species – SIVANTO® Prime. SIVANTO® Prime belongs to a different group (IRAC Group 4D) and offers a different mode of action compared to the existing pesticides currently on the market. What makes SIVANTO® Prime unique is that it is inspired by the plant Stemona japonica, a medicinal plant with natural insecticidal properties found in Southeast Asia. The active ingredient, flupyradifurone, is based on stemofoline – a natural isolate from Stemona japonica. Although scientists worldwide have been trying for decades to utilise this plant for crop protection, Bayer has succeeded in identifying a specific component with insecticidal properties.
The stem foil (stemofoline) is an alkaloid with exciting insecticidal properties. By combining the butenolide pharmacophore structure with two other chemical fragments, Bayer scientists have significantly improved the efficacy and selectivity of the active ingredient.
SIVANTO® Prime provides long-lasting protection by rapidly stopping the feeding activity of insects, reducing crop damage and protecting yields. The product works systemically, as well as on a translaminar systemic level, and is effective against feeding aphids.
This modern, environmentally friendly insecticide has an excellent safety profile and poses no risk to honeybees or bumblebees.
Resistance management: Key to sustainable pest management
An important aspect of resistance management is the rotation of chemical groups, as well as the support of natural control mechanisms to keep pest numbers low. Excessive use of specific IRAC groups promotes the development of resistant populations. Every pest population contains individuals that may be genetically resistant, and mutations may arise that are resistant to certain active ingredients.
This is one of the reasons why resistance to certain aphid species is already being observed in areas such as the Swartland and Southern Cape. Economic pressure sometimes forces producers to repeatedly use cheaper products without rotating IRAC groups.
The key, therefore, lies in the careful and discerning use of insecticides – different classes of insecticides with differing modes of action must be alternated from year to year. By using SIVANTO® Prime, which falls into Group 4D, resistant insect populations can be controlled to keep pest levels as low as possible.
Contact your nearest Bayer representative for more information on SIVANTO® Prime.