Grain Guide 2016

104

GRAANGIDS

2016

GRAIN GUIDE

Watch out for

GERBILS

If you have not yet encountered gerbils, it will definitely happen at some stage. All grain farmers

must be aware of the possible occurrence of gerbils in their production areas.

Be on the lookout for burrows with a diameter of 60 mm in the headland and on the sides of

cultivated fields. If you find such holes, it is definitely time for an anti-gerbil campaign.

Gerbils must be hit hard when they are at their most vulnerable, namely at the end of winter

in the summer rainfall areas and at the beginning of autumn in the winter rainfall areas. This

is when the animals are hungry and will react the best to rodenticide bait.

Only registered anticoagulant rodenticides registered for gerbils, as well as zinc phosphide

and aluminium phosphide, may be used. Anything else – for instance aldicarb and carbo-

furan – will not have the desired effect and it is also a criminal offence under Act No. 36 of

1947 to use such substances.

The anticoagulants must be administered in 750 mm long 75 mm irrigation pipes: string

three or four cubes on a thin wire and then hide the wax cubes inside the pipe, where the

gerbils can eat them and other animals cannot reach them. Place the bait pipes 50 m apart

around the field, or even within the field where there are colonies. Supplement every fourth

day until the population has been eradicated. Pick up dead gerbils and bury them.

Zinc phosphide can be used as ready-to-use bait or producers can prepare their own bait:

Soak cull maize in water until it germinates. Dry quickly and then mix according to instructions

on the label with zinc phosphide and cooking oil. Use the same pipe as for the anticoagulants

and place two tablespoons of the bait in the pipes, every 50 m around the field. Such bait can

also be placed directly in the burrows (use a 25 mm pipe and a funnel), and close up the bur-

rows. Zinc phosphide kills them quickly and the animals seldom die above ground. Under no

circumstances should you distribute the bait across the fields with fertiliser dispensers or plant

seed that has been treated in this manner! This would be totally ineffective and holds the risk

of poisoning.

Bait drums can also be used: cut a 210 litre drum in half and plant it level with the ground.

Fill one-third with water and sprinkle sunflower seeds on the water. The gerbils drown when

they jump into the drum to eat the seeds.

Plant seats for owls and raptors. One pole 2,4 m tall every 50 m, and one pole 1,4 m tall

every 50 m. Sprinkle seed around the pole in the late afternoon so that it attracts the gerbils

and the owls can hunt them. Also construct an owl box: One owl box per 50 ha is sufficient.

Plant a bait crop of cull seed in the headland at the same time the crop is planted. The bait

crop should be densely planted so that the gerbils prefer to eat there rather than in the crop

itself.

Where conservation tillage is implemented, the risk of gerbil infestation is almost 100%, as the

abolishing of deep tillage means that the colonies are no longer destroyed. Such fields where

gerbils flourish should be ploughed thoroughly and deeply once every four years.

For a complete management plan for gerbils, email a request to

Dr Gerhard H Verdoorn (Griffon Poison Information Centre

and Association of Veterinary and Crop Associations of

South Africa [AVCASA])