Disease | Symptoms | Cause | Comments | Management |
Anthracnose (Glomerella Cingulata) | Dead leaf tip, defoliation, brown or purple lesions and necrotic spots | Fungus | Spread by rain, high moisture and warm temperatures encourage spread | Prune dead twigs and branches from tree before fungi produce spores, remove dead leaves |
Scab (Sphaceloma perseae) | Irregular brown or purple spots on fruit with rough texture | Fungus | High humidity encourages scab growth and spread | Spray copper containing fungicides |
Stem-end rot | Shriveled tissue at stem end, black lesions at stem and eventually over entire fruit | | Environmental conditions, spores can spread by wind or rain | Prune dead limbs and twigs, prune and harvest in dry conditions, apply thick layer of mulch |
Phytophthora Root Rot (Phytophthora cinnamom) | Black lesions on roots, black, brittle roots, small yellow leaves, decline in fruit yield | Oomycete | Wet soils encourage Phytopthora infection, plant in a well drainage soil | Prune out dead limbs and twigs, remove fruit from the ground, Minimize wet splash between trees |
Bacterial soft rot (Erwinia herbicola Erwinia carotovora) | Gray to black, mushy, foul smelling rot on fruit | | Bacteria may be present on leaves but do not cause damage unless plant is stressed or bacteria enter the plant through a wound | No treatment for disease, remove plant debris from soil, use certified seed |
Sunblotchs (Avocado sunblotch virodi – ASBV) | Red, yellow, pink or white streaks running the length of young stems | Viroid | Can be transmitted by grafting | Sanitize all pruning equipment with disinfectant |
Western Avocado Leafroller ( Amorbia) | Defoliation of tree, scarred fruit, young larvae are yellow-green and mature to dark green and a short, dark horizontal line on the side of thorax | Insect | Female can lay between 150 to 200 eggs during her life time, insect generally undergoes 3 generations per year | Application of selective insecticide such as Bacillus thurengiensis help to conserve populations of natural enemies |
Avocado thrips (Scritothrips perseae) | Feeding scars on fruit,adult insect is orange-yellow in color with distinct brown bands | Insect | Insect thrives in cooler temperature, insect may undergo 6 or more generations per year | Organic mulch about 6 inches thick below trees may help to reduce survival of thrips pupating in soil, insecticide recommended to reduce damage to populations of natural enemies |
Algal leaf spot (Cephaleuros virescens) | Orange red-spots on both upper and lower surfaces of leaves, spots may coalesce to form irregularly shaped patches | Alga | Disease affects many fruit trees in the tropics, infection is unsightly but often harmless | Ensure trees are properly pruned and fertilized to promote vigor, remove all weeds from around tree bases, badly infested trees can be treated with copper containing fungicides |
Persea mites (Oligonychus perseae) | Defoliation, mites cause the development of circular chlorotic to brown spots on the undersides of the leaves and fruit surface | Arachnid | Persea mites are most damaging on Hass and Gwen varieties | Ensure the tree is adequately fertilized, pruned properly and irrigated to avoid unnecessary stress to the tree |
