What’s Wrong With My Holly Tree – Shriveled And Sand-colored Leaves? Leaf Scorch Or Not?

Question

Hi! I’ve read a lot about holly tree leaf scorch problems but I still can’t figure out if that’s what’s happening to my holly trees. I live in Phoenix AZ infamous for its extreme summer heat. I plated three holly trees in my back yard in early April (a bit too late). They lined up from north to south, with the south one getting about 8 hours of direct, unfiltered sunlight; the north one getting about 6 hours. Soil is the typical type here made up of decomposed granite mixed with gravel. A while after planting them I’ve started to notice leaves starting to die! First the tip of the leaf dries out — color turns to light, sand color mixed with darker brown. Soon after, the water-wave color pattern takes over most of the leaf and the fleshy leaf turns to a dried, crispy chip. The problem almost always starts at the leaf at the tip of a branch and proliferate up to the trunk. New leaves are seemingly also more susceptible. I do have noticed that, the tree planted at the north-est location remained unaffected for quite a while, yet it started to show scarce examples of this problem these days. The two planted to the south is affected all over. I water these trees thoroughly every 3 days in the morning. Given the drainage of the soil and the Arizonian heat, I tend not to think it’s due to overwatering. I adjusted the soil pH to around 6.0 which AFAIK is good for holly trees. I also used neem oil to get rid of some spider mites which at one time infected a couple of leaves, and at this moment I can’t visually see any pest with naked eye. So what could have happened to my poor holly trees and what I can do to help? The symptoms do not seem to be those commonly show with leaf scorch. Could it be because they get too much sun? Or could it be bacteria or fungi? Thank you very much!

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Answer 1

Neem oil should NEVER be sprayed when there is direct sun. Than, on top of the infections that spider mites cause, will be a recipe for the plants' death, unfortunately.

Try and wash off as much neem oil as possible. This may require a very light spraying of diluted soapy water (which is also a good defense against spider mites). Once this is done, apply a copper based fungicide to get rid of any pathogens brought about by the mites.

Recovery from mite damage will take a long time. There will be infections to work through, as well as the attempt to keep further insect damage at bay. With proper care and attention, this will be an easy task.

In the future, you may turn to Azadirachtin This is the active ingredient in neem oil. This cuts out the chance of sun burn from neem oil.

Here are some articles that will help:

https://www.gardeningknowhow.com/plant-problems/pests/pesticides/azadirachtin-vs-neem-oil.htm

https://www.gardeningknowhow.com/plant-problems/pests/insects/spider-mite-tree-damage.htm

https://www.gardeningknowhow.com/garden-how-to/info/using-fungicides-in-garden.htm

https://www.gardeningknowhow.com/ornamental/shrubs/holly/growing-holly-bushes.htm