The Moroccan fauna is very rich in rodent species considered harmful to agriculture and this is due to the damage caused especially on crops such as cereals, sunflowers, vegetable crops, groundnuts, etc.. There are two main groups:
- Citrus rodents: species that live in the fields and attack spontaneous crops and plants such as Shaw’s Merino (Meriones shawi) and Gerbille (Gerbillus campestris);
- Anthropophile rodents: species living with man in settlements, stables and warehouses. These include Rattus norvegicus, Rattus rattus and Mus musculus. It should be noted that the control of this group of rodents is the responsibility of the Municipal Offices of Hygiene.
For rodents, damage by Shaw’s Merino and Gerbil can be classified into three types:
- Direct damage to crops under attack;
- Losses due to storage of seed reserves in burrows;
- Losses on the arable land area caused by burrowing.
The most dominant species and the most adapted to the different types of habitats, distributed over almost two thirds of the country is the Shaw merino. It causes considerable damage to wheat and barley crops. Attacks can occur from seeding to cereal maturity. At the seedling stage, heavy attacks are characterized by the appearance of areas without vegetation at the field level. When the seeds mature, the ears are completely cut and transported for storage in the burrows. The stored quantities can reach 13 kg on average per burrow. Meriones can also attack other crops such as vegetables, pulses and arboricultural crops. In addition to crop damage, this species is recognized as a reservoir of the causal agent of cutaneous leishmaniasis, a disease transmissible to humans and which affects several regions of the country (Tata, Ouarzazate, Errachidia and Figuig).
With regard to gerbil, the most important damages are those committed in the peanut crop and especially at the maturity of the pods. In fact, the quantities of groundnuts stored in the burrows sometimes reach 5 kg. These quantities can well exceed this figure in case of strong pullulation.
The protection of cultivated plants from field rodent attacks is achieved through the monitoring of populations of these pests and the implementation of control campaigns carried out mainly by the use of poison bait. The control campaigns, conducted in close collaboration with local authorities, are supervised by the regional plant protection services.
Finally, it should be noted that studies on the biological activity of Shaw’s merino show a strong correlation with the quantity and quality of plant cover and rainfall. This correlation is an important indicator for predicting the extent of this species’ outbreaks in usual areas of infestation.
Rodent control is particularly difficult because these animals are highly adaptable. Their behaviour and lifestyle reveal great intelligence, and are also very prolific.
Rodent control measures are aimed in particular at keeping rodent populations harmful to agriculture at a tolerable level. They are governed by Gubernatorial orders issued by local authorities. These orders define the zones, periods and techniques recommended in this regard.
During large-scale operations, the treatments are done collectively by the farmers with the guidance of the technicians of the Plant Protection Service. These treatments are done in the presence of local authorities. Before each operation, farmers receive a demonstration on the use of bait and the precautions to take during the treatments.