Gerbils plague maize farmers

Farmers in the summer grain regions were battling to get gerbil infestations in their lands under control, with about 5% of their maize crops destroyed.

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The Highveld gerbil (Gerbilliscus brantsii) commonly known as the Springhaasrot or nagmuis, affects maize crops in South Africa. More recently, infestations have escalated to the point where Grain SA has appointed a task team to investigate possible solutions to the problem.Grain SA’s research showed that gerbils destroyed 55 000ha of maize in the last season.

About 500 producers had responded to Grain SA’s survey. Cobus van Coller, Grain SA executive member in Bothaville, said the gerbil problem had reached crisis level. The worst affected area was Hoopstad in the Free State with 20% of the area’s maize crop destroyed.

Crop losses
“The problem was exacerbated about four years ago when no-till farming techniques became more popular, but has worsened in the last two years,” said van Coller. When lands are tilled, populations are partly controlled by burrow destruction. “Gerbils can cause enormous damage easily working through 50ha in a two-week period. They are prolific breeders capable of producing a large number of pups in a year,” said van Coller.

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Farmers used a combination of techniques, including attracting owls to catch gerbils. However, gerbils are poisoned when numbers are too great for control by other methods. Francois Enslin, Mpumalanga maize and soya bean farmer, said gerbils were a big problem on his farm. “They will eat through an entire land of maize. When you look again there is a whole patch of maize, in the middle of your land, missing.” Enslin used an aluminium phosphide fumigant to control gerbils.

Frikkie Kirsten, of the Plant Protection Research Institute, has been tasked by Grain SA to investigate effective methods of gerbil control. He is in the process of acquiring funding, but said that producers could expect answers by the next maize planting season. “We need to get the problem under control fast. After that, we will be looking at long-term, more environmentally friendly solutions,” said Kirsten.

He explained that the timing of poison applications was crucial. “It must be done either before planting or before harvest. If it is done after harvest there is too much food on the land for the gerbils and they are less likely to eat poison bait.” Kirsten asked that any farmers who had found effective ways of controlling gerbils should contact him on 012 808 8217.

For an updated rodenticide protocol contact Dr Gerhard Verdoorn on 082 446 8946 or email him at [email protected]