As NAREI in Focus continues to look at avocados, this week readers will be informed of DISEASE MANAGEMENT.

 Three main fungal diseases affect avocado: 
• Avocado root rot (Phytophthora spp.)
• Anthracnose (Colletotrichum gloeosporiodes)
• Scab (Elsinoe perseae)
1. Avocado Root Rot (Phytophthora spp.):
Symptoms: Leaves are smaller, pale, wilted, and fall giving the tree a sparse appearance. This is accompanied by dieback of twigs and branches, fruit drop or small fruits, and defoliation. Watering too often or with excess amounts increases avocado root rot.

Control: The best method of control for this disease is its prevention in the first place. This is done by the use of disease-free planting material, use of sterile tools in grafting, efficient drainage and irrigation, and use of resistant rootstocks. The disease may be treated with a soil drench of Metalaxyl (Ridomil) at the rate of around 0.15g/ml. The measurement here refers to the canopy of the tree.

1. Anthracnose (Colletotrichum gloespoiroides)
* This disease affects immature fruits and shows up when fruits ripen as small, brown, sunken lesions, which soften 7-15 days after harvest. This leads to fruit deterioration.

Control: This may be achieved by the routine spraying of a Copper Fungicide such as Kocide from the onset of flowering to fruiting at a rate of about 5 ozs. (140g) in 1 gallon (4.5 L). The fruits may also be dipped in a fungicide solution, e.g. benomyl mixed at 1/2 oz/0.8 gallons (1 5g/4L) water. This treatment prevents the disease from showing up on the fruits.

1. Scab (Elsinoe perseae)
Symptoms: Raised cream coloured to pale brown/orange warts are seen on the fruit and leaf surface.

Control: Pruning to increase air-flow within the canopy of the tree may be done to reduce the incidence of this disease.