Guava fruits turning black and shriveling

Guava    Puerto Rico

My tree is a little over than a year old and it's a product of grafting. I planted it on March of last year and it bore fruit for the first time on or near October. It was just a couple of fruit, but they were delicious. Now the tree is full of fruit but there are two problems:

1. Before they ripen, most are turning black and drying up.
2. Others develop some sort of eruptions.

P.D. I also noticed a lot of ants going up and down the trunk and black mold(?) on some leaves.
P.D.D. I tasted some of the normal-looking guavas and they're not as sweet as last years'.

Posted by: Carolene (2 points) Carolene
Posted: October 7, 2014


The "eruptions" on the fruits are scale insects that are tended by ants for the sweet honeydew they excrete and upon which the ants feed. The black mold on the leaves is sooty mold, a non-parasitic fungus that grows on the thin film of sooty mold that falls on leaves. One must control the ants to manage the scale and sooty mold problems.

The black, circular rot at the blossom end of the fruits ("blossom-end rot") may be a calcium deficiency, which can be corrected by applying a source of calcium fertilizer (Ca) such as agricultural lime. The entirely black fruits may be a severe expression of the calcium deficiency.

Posted by: Scot Nelson (3 points) Scot Nelson
Posted: October 13, 2014

Carolene commented,
Thank you! That sounds pretty logical! I'll try that out!
almost 6 years ago.

I would just like to ask a few further questions about your tree for clarification. When the tree first bore fruit did they ripen properly so that you could harvest and eat them or have all the fruit turned black? Also, does the black coloration first appear as spots which spread to cover the fruit?

There is a possibility that this is anthracnose but this would begin as sunken spots on the fruits which coalesce. The fruit would not simply turn completely black overnight.

When you cut open a fruit what does it look like? Can you add a picture?

Posted by: Lindsay McMenemy (2 points) Lindsay McMenemy
Posted: October 9, 2014

Carolene commented,
Thank you for your interest, Lindsay! When my tree first bore fruit last year they did ripen properly and though they were only a few, the guavas were delicious. This year, the tree was full of little guavas when suddenly most started turning black. It seems like black coloration comes out of nowhere. I should also add that my tree is a product of grafting. Moreover, there seems to be some black mould? in some of the leaves. Finally, I have tasted some of the normal-looking fruit and they're not as sweet as last year's. I'll add more pictures.
almost 6 years ago.

Update October 14th 2014
How to tell if ants are the problem

For this tree there is a suggestion that ants are causing damage because of their relationship with plant sucking insects. How can you tell.
1) They are running up and down. Ants require sugar and protein. When you see ants moving up and down a tree trunk going towards the canopy it is most likely they are collecting sugar and bringing that back to their nest. Ants do form trails to collect protein (usually a dead insect) but it is much rarer and would not last for many days as they would quickly exhaust the protein supply

2) At some points in the canopy, under the leaves, on the fruit or on twigs you will see little bumps. These are the plant feeding insects. You can see different stages on the guava photo; larger ones that are colored and smaller ones that are whiter. You need to approach these very slowly and you will see the ants tending them. The ants are after sugar and these insects secrete this sugar. By moving the leaves, fruit or blowing on them you can cause the ants to leave the insects. But be patient. You will see them

Now. Control.

The ants are likely not nesting in the crown of your tree. But try to find out if the trails are going into any holes.

Lets assume they are nesting elsewhere and coming to your tree for sugar. Then you can block them on the trunk using a sticky substance called ant guard, over which they dont pass. You should also spray them off with water and/or soapy water, creating. This is also good for removing the plant feeding insects. It will also help remove that mold. See more details on a previous answer I gave here

I would like to know where the ants are going and if you can see them collected around groups of insects on the underside of leaves. I think there could be a sooty mould problem where the insects feeding on the tree release sugar as honeydew and this promotes the sooty mould (as black growth)
Would like a sharper picture of the fruit too

Posted by: David Hughes (54 points) David Hughes
Posted: October 10, 2014

Hi! I don't see the ants collected in groups under the leaves. They're mostly running up and down the trunk and some are on the leaves. I believe the black mold (?) on the leaves is connected to the eruption problem (see new photos). Thanks for your interest!

Posted by: Carolene (2 points) Carolene
Posted: October 14, 2014

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