By Umar Nsubuga
There are different species of aphids which attack cabbages. The cabbage aphid (brevicoryne bressicae) appears as masses of soft, pale green insects covered by a mealy powder.
They feed in clusters on the underside of leaves and occasionally on stems.
Gideon Zakke, an agronomist says infested leaves become yellow and If infestation occurs on young seedlings, they become stunted and distorted. Heavy infestation may cause the death of seedlings.
“Amongst the aphid colonies, there are numerous white cast skins and drops of honeydew which act as substrate (medium), for the growth of sooty mould fungus (black fungal growth). These are dangerous insects and annoying pests. They transmit more than 20 virus diseases in the cabbage family (cruiferae),” he explains.
It is the females who are dangerous. The adult females either winged or wingless are covered by a grey, mealy, powdery wax which masks the green colour of the aphid. These adults produce living young, he adds.
Control
-Dry weather favours heavy infestations. With heavy infestations, it is better to spray with decamethrin or oxydemeton-s-methyi.
These come under different trade names but the farm shop manager will assist. Check for chemical names whenever you are buying pesticides or herbicides to ensure you are carrying the right chemical.
-Care should always be taken to use only environmentally friendly chemicals.
