For wheat pest management in South Africa farmers should regularly scout their lands to identify insect and disease problems before these get out of control.
Certain pests and diseases may be treated curatively, while others should be treated preventatively if conditions foster their development. Pesticides, however, should never be regarded as a silver bullet, but be used in combination with conservation farming practices, such as crop rotation, the minimum disturbance of the soil and stubble retention, as well as the use of pest tolerant cultivars, certified seed, proper soil preparation and management practices to prevent problems.
The general consensus being that plants planted in good soils are able to withstand much more environmental stress and diseases than plants planted in poor soils.
When it comes to pest management, it makes sense to build a relationship with a chemical consultant or farm technician to help you correctly identify and manage pests. Even well-established commercial farmers do this, as they realise that it is impossible to know everything about production.
Changes in climatic conditions are also resulting in shifts in insect population and diseases, resulting in these appearing in regions where they did not previously occur, and also at times that were previously unheard of. Different insects attack different parts of the wheat plant, above and below the soil. The Agricultural Research Centre identifies the following pests as the most important in wheat pest management.
Seed and Stem Damaging Insects
Black maize beetle, greater false wireworm and lesser false wireworm sporadically occur throughout the summer rainfall area. These insects feed on the seed and stems of wheat seedlings just beneath the soil surface, causing the plants to wilt and die. Wireworms cause damage while in their larval stage, while the black maize beetles cause damage when they are in the adult phase.
Larvae of the Western Province grain worm and Sandveld grain worm cause seed and stem damages in the Western Cape. Western Province grain worm strikes usually occur after heavy rains.
Seed treatments and cultural practices supporting germination and rapid wheat seedling growth help to reduce the vulnerability of plants to these insects. At the moment there are no chemicals registered to control Western Province grain worm or Sandveld grain worm.
Leaf and Stem Attackers
Russian wheat aphids occur in the summer rainfall area of South Africa. They attack both the leaves and stems of plants, causing the leaves to turn white, yellow or purple. The use of resistant cultivars is the best control option.
When chemical control is used, farmers should ensure they use a product that targets the specific biotype that is causing damage on their farm.
Ear Attackers
Bollworm, brown ear aphid and oat aphid primarily attack the ears of the wheat. Bollworm specifically is primarily a problem in the Western Cape and wheat fields under irrigation. The larvae feed on the chlorophyll of the leaves resulting in white blotches and streaks.
The larvae move into the ear of the wheat as the crop matures, resulting in direct yield loss as well as lower quality. Chemical intervention should be considered when 10% of the ears are infested with one or more larvae per ear.
By Glenneis Kriel