LAST week, NAREI in Focus began looking at avocados. This week we will focus on aftercare, pest and disease management.

AFTERCARE 
Training and Pruning: Avocado plants should be pruned to encourage branching to ensure a good framework. Pruning should be practised after harvest to remove deadwood, as well as to maintain the framework of the tree. Avocado plants are brittle and break easily; thus, windbreaks should be planted.

Fertilising 
Fertiliser needs are directly related to the type and nutrient status of the soil. It is essential therefore that a soil analysis is conducted to determine these factors for the particular location. However, in the absence of precise soil analysis, the following might suffice Clay Soils – Compound Fertiliser 12:12:17:2 at the rate of 1/21b (225g) to 2lbs (0.9kg) depending on the age and size of the plant is applied twice per year, usually at the beginning of each wet period.
Sandy Soil – the above is to be used at the higher rate as well as 9:27:9 +FTE at the rate of 1/41b (112 g) to 1/21b (225 g) per plant once per year.

PEST MANAGEMENT 
There are no major pest problems with the Avocado. The most serious are Mites and Scale Insects and these could be controlled by the use of Danitol (Fenpropathrin) or Rogor (Dimethoate) at 0. 02 pts per gallon (10 mls/4L).
• It should be noted that the occurrence of any unusual pest or disease must be reported to the Crop Protection Section at NAREI for investigation.

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.)
* 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 (Figure 2). 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 (Figure 3).

* Control 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.