I have been told that fungus causes failure to set fruit and fruit drop. I was told to spray the tree with copper fungicide weekly from first blossom until fruit set. I just finished the first trial and can't tell yet the results. Seems that it couldn't hurt.

A dramatic change in the weather -- such as wind, high temperature, and/or very low humidity --can cause avocado fruit to drop.

jean

Try a good mulch with a good compost and added potash, usually helps with trees that have trouble setting and keeping flowers that set fruit. works for all fruit trees, they must have the potash to get good flowers and fruit set.
Avocados are a very hardy beast, but don't like wind.
GayT

There are many reasons for fruit drop.

The first consideration is pollination. Many avocado trees require two different cultivars to insure pollination because they are either type A or B flowering. Having a second plant of the opposite stage increases the potential for pollination. There is a need for both a source of pollen and the receptive female phase of the flowers, plus a pollinating insect to achieve fruit.

Small fruit, subject to low temperatures, will likely cause the developing seed abort. In most cases the fruit drops, but in some instances the fruit continues to develop without the seed enlarging - this fruit is termed "cukes" by growers and sometimes sold as "cocktail avocados" by enterprising produce people.

Strong winds produce a wind chill effect on the plant and result in damage to small, developing fruit by lowering its temperature below what an air temperature reading reports.

Try constructing a 3 sided plastic wind break around the tree and see if this helps. You might also see if there are sources of named cultivars of avocados in your area and graft several different selections to replace some branches.

Good luck.

Claude Sweet
San Diego, California
USA

I have a 7 years old avocado tree (from a seed) last year I had some flowers; they all ended up on the ground; this year I got a ton of flowers; they are gradualy falling down. will I ever have fruits? do I need to graft it and how? or I should wait. it is a very health tree

Hi Jeff, I live in Nassau Bahamas and moved into a new apt. a year ago with a very large backyard. It has a fully grown avocado tree that got blown down in a hurricane, but has regrown and has termite infestation like all my large fruit trees. My tree had a lot of baby fruit that blew down during some high winds and I only harvested 4 very tasty fruit. This year I am more prepared and did a lot of pruning and composting and watering. More fruit are staying on the tree, but a few are turning black and dropping. I think the key is to give it a good soak every week and we will both have a good harvest this time. Later, Mike.