What to Do about Brown Spots on Avocado Leaves
If you have noticed the leaves of your avocado tree browning and are concerned about the health of your plants and the state of your tree, there are several causes and solutions to keep your avocado trees healthy and free of brown spots.
Causes
Harsh Elements
There are several cause for your avocado leaves to be browning. Some are due to the outside environment and may be out of your control. If you live in an area where the climate is harsh or you are overexposed to certain elements, it can cause browning in your avocado leaves. Some of these harsher conditions include drying winds, frost, ice, and harsh sun rays. Salt can also become an issue in some climates because it gets carried through the air and too much salt exposure is bad for your tree.
Soil Changes
If you are not using mulch, or have recently moved or disrupted the mulch you already have, it could be impacting the about of water the tree is getting. Watering around five gallons straight to the ground a couple feet from the trunk will keep your avocado tree properly moisturized and prevent browning. Watering your plant with half the water, then waiting for the ground to dry completely before adding the second half and maintaining a good layer of mulch can keep your tree happy and healthy.
Root Disease and Fungus
Seedling Blight
When a tree is infected with this particular fungus, leaves will show reddish brown spots .These spots will be larger along the vein of the leaf. Typically this disease presents itself after heavy rainfall and high humidity. The best way to combat this is to strike early on. When the tree is still a seedling it should be grown on a bench and soil should not be used because you risk introducing pathogens to the plant. You should also avoid irrigating from pond or still water. Keeping air circulating and enough space between plants is vital in growing healthy avocado trees. If your tree does become infected, fungicide will need to be used.
Scab
This particular fungus not only shows up as brown spots on leaves but also on the fruit itself that looks like brown circular scabs. This fungus usually makes itself known when the tree is still young and exposed to cool and moist weather. Fungicides should be used when flower buds appear.
Mites
Persea mites can cause brown circles on the undersides of leaves and on the fruit itself. These pests start to make an appearance in mid-March, and can continue to be a problem through October. Make sure to check the undersides of the leaves every week or so to catch this early on. Don’t use a leaf blower to try to remove the mites.
Depending on the where you live in nature may take care of the problem for you. The Persea mites are prey for black hunter thrips, brown lacewings, and rove beetles. If you see any of these insects you probably won’t have to spray – give it a week or so to see if nature handles the problem for you.
If these insects are not in your area you will have to treat the problem yourself. Your choices are either a chemical solution available at any gardening store, or a more eco-friendly option of several horticultural oils and/or spraying the underside of the leaves with water to keep the mites from attaching to them. Choosing these latter options means you must be a lot more hands on and make sure to stay persistent in your treatment.
How To Prevent Avocado Tree Problems
Keep your tree watered and make sure to have a protective layer of mulch to help keep the tree well hydrated. Mulch helps reduce the effect of saline water on the tree. Gypsum should be applied under the mulch – as much as 25 pounds for a medium sized tree. This provides needed calcium to the tree and reduces the chances of Root Rot occurring.
Avoid getting the trunks wet or waterlogging the roots. This will cause leave and fruit problems if done repeatedly. You’ll also want to check the alkalinity and salinity of your water source – poor water will result in tree issues.
Getting your soil tested to see if it has enough nutrients for growing avocados is also a good idea. If you are having repeated problems in keeping your trees healthy, your soil could also have other problems besides nutrient deficiency and be harmful for your avocados. The best time to test for nutrients is late summer to early fall. Gather some new-growth leaves, ones that expanded during the past year. You can send those to the lab for a test to see what areas the tree is lacking in.
Treatments
If the browning has spread from just your leaves to the branches and trunk you will have to figure out how far it has truly progressed. You can do this by cutting little bits of the wood at a time and seeing where the brown turns back to green. Everything brown will have to be cut off before it spreads to the whole tree. Getting a professional opinion might be helpful before you start cutting so you can save as much as possible, while getting the infected parts fully removed.
If it is a mite problem, once the pest is dealt with the tree should recovered relatively quickly. Keep records rather than relying on memory – if there isn’t progress in a few weeks call a tree expert.