name this mango disease

Mon Plaisir, Aruba

Hey tropical party people,

My valencia pride mango tree is now about 12 feet tall and seemingly doing very well. On closer inspection though, large sections of the foliage are covered with little black dots (see the attached picture of a representative leaf). What is this disease, and how can I treat it? Googling didn't turn up an answer, so I'm turning to you, my worldwide tropical gardening experts. Thanks!

Thumbnail by happyisland
Keaau, HI

It is a scale-insect. You can treat them with soap.

Mix 4 ounces of mild shampoo per gallon / 4 liters of water (1 oz per quart / liter). Spray and saturate the affected areas of the tree. Repeat every 7 days till the bug appears to be gone.

This is a safe and non-toxic method to get rid of scale insects. The bug breathes through holes in it's back. The soap clogs the holes in the bug's back and suffocates it.
There is no resistance to suffocating and the bugs get removed without putting toxic pesticides in an area, keeping people, pets, and wildlife safe.

If the area is very dry, rinse down the treated area a day after spraying. The bugs that get saturated should suffocate within an hours time. A safe method is to spray down the plant in the evening, and wash the plant off in the morning.
To be cautious, it may be good to spray & wash down the whole tree. Check neighboring plants for other colonies.

If you kill them before they become numerous on the plant, the problem is easy to get rid of.
The worst place for the scales to congregate is around the budding new growth of the plant, as they will deform it.

Aloha, Dave

Mon Plaisir, Aruba

Thanks for the tips, Metro! The tree just had a beautiful flush of new growth, so I'm going to have to do your treatment before the bugs spread.

Since you were so good on this one, what do you think is the deal with the diseased citrus leaf (pic attached)? Virtually all of the citrus trees in Aruba have this freckling of leaves - there is no pest visible to the naked eye though. It doesn't kill the tree, but it can't be good for them...

Thumbnail by happyisland
Keaau, HI

Best I can tell is it is a type of fungus or lichen. It would be good to see it under a microscope.

If you have an agricultural extension service it might be worthwhile to show it to someone there.

Mon Plaisir, Aruba

I just wanted to report back on that citrus leaf. I got the government tree specialist to come out and have a look and he diagnosed this as the Citrus Hindu Mite, Schizotetranychus hindustanicus. I'll start treating it with a spider mite spray called Avid this week. He says that you have to treat the leaves every 8 days because the poison does not kill the eggs, only the living insects. Anybody out there have any experience dealing with spider mites on citrus? Any especially lethal tactics (that won't kill the tree too)?

Keaau, HI

Plenty of tropical mites in Hawai'i!

They have a life cycle of a few weeks, so they must be treated every week for about a month. Then treat every two weeks a couple times.

Be aware that the mites could be coming from habitat close to you, so reinfestation may be an ongoing problem.
Good to have a look around and see if other species are infested.

Also good to keep the nutrition and growing conditions to an optimum, which allows the plant to utilize it's natural defenses against attack & disease. In a healthy environment, predator mites and other carnivorous bugs will show up to equalize the affects of the herbivorous bugs!

Aloha, Dave

Mon Plaisir, Aruba

Thanks dave,

I treated my infected citruses with avid and will follow up on them in a week. I also sprayed down my mango with your shampoo concoction to get rid of its san jose scale. I'm not sure how to tell if these treatments are working or not, since the injuries remain even if the bugs are dead. I guess I'll know in a few months if the new growth stays clean.

Unfortunately, my neighbor has a severely mite-ridden grapefruit shrub just across the wall, so it looks like the citrus treatments will be ongoing. Do you know if there are any side effects to the tree of repeated and ongoing use of avid?

Keaau, HI

Not sure if the tree will have any symptoms. Be careful of getting the stuff on yourself.

Maybe you could offer to treat your neighbor's Citrus, which could help control the pest on your land.

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