Widespread outbreaks of gerbil infestations have been reported in the summer grain production regions, with damage being reported in the Free State, North West and KwaZulu- Natal. This was according to Dr Gerhard Verdoorn, CropLife SA’s operations and stewardship manager.
Verdoorn said various species of rodents fed on crops, depending on the nature of the crop, as well as the biome in which the crop was produced. In the summer grain production regions, gerbils posed a particular problem.
While gerbils dug up grain seeds immediately after planting, they caused the most damage when seeds began germinating.
“This is most probably due to the seeds being soft and more palatable than when newly planted. Gerbils are small rodents with short tails and long hind legs. Colonies of thousands of animals/ha are not unknown,” Verdoorn explained.
Gerbils were able to dig as much as 30m away from their burrows on the edge of a crop field to reach the seeds.
Populations could be expected to explode in the first weeks after planting due to the ample food supply.
It was therefore essential that producers started implementing precautionary measures as soon as possible.
“Daily scouting for gerbils is of the essence. This is the only way colonies can be timeously detected. Its’s obviously much easier to manage small and isolated outbreaks [as opposed] to huge ones,” he added.
Verdoorn advised farmers to only use registered rodenticides as listed in CropLife’s gerbil management plan.
These rodenticides needed to be placed in bait boxes or gerbil burrows. Scattering rodenticides onto the soil surface was not only illegal, but ineffective and posed a severe risk to biodiversity, as did the use of products that were not explicitly registered as rodenticides to be used against gerbils.
“We also encourage grain farmers to create an environment that is conducive to owls and diurnal raptors, such as erecting owl boxes. These birds are valuable assets in gerbil control,” Verdoorn added.
According to the Food and Agriculture Organization of the United Nations (FAO), gerbils were nocturnal and terrestrial. They usually walked on all fours, but when alarmed, they could flee in running bounds of up to 1,5m in height and more than 3m in length. They had powerful, well-developed hind limbs and were mainly granivorous.