Like humans, trees can become sick. But unlike humans, trees do not have specialized cells to fight off diseases. So, it is important to do what you can to improve the health of your trees.
In a drought year like this, many trees have low immune systems due to a lack of water. Trees under drought stress are more susceptible to pest problems, such as aphids, bark beetles, mountain pine beetles, spider mites, western pine beetles, and more.
Arborists recommend using a triage system for watering your trees if you are under water restrictions. If you are not under water restrictions, supply your trees with ample amounts of water, and watch for other signs of sickness.
Tree pruning is also essential as suckers and dead or diseased branches can steal nutrients from the main system of a tree. Deciduous tree leaves may begin curling, bending, mottling, rolling, scorching, shedding and producing autumn colors early.
Conifers may have yellowing or browning needle tips in a drought. Learning the signs of a poor immune system in your trees will allow you to detect problems early and strengthen your trees’ ability to survive in harsh conditions.
In these harsh drought conditions, your trees may show signs of nutrient deficiency, which lowers the tree’s ability to resist diseases caused by bacteria, fungi, viruses, Oomycetes, nematodes, or insects. There are different kinds of nutrient deficiency in trees, all caused by a lack of vital minerals.
A soil test will indicate what your soils may need. Nitrogen deficiency causes tree leaves to look yellow, with possible pink tints. Nitrogen is often washed out of the soil in the winter, leaving little left over for spring growths.
Some ways to introduce nitrogen back into the soil is by mulching with organic matter, rotted garden compost or manure. Having chickens walk in the areas where organic matter is being introduced can be helpful as they will mash the materials into the top few inches of soil and spread their own natural manure on the site.
Potassium deficiency causes yellow or purple leaf tints, browning leaf edges, or poor fruit and flower production. Potassium deficiency is one of the most crucial because trees need potassium for photosynthesis, water uptake and general hardiness.
Spreading potassium sulfate into the soil will boost your trees’ immune systems and help them fight off diseases. Potassium helps improve disease resistance and lessen water loss, and sulfur builds up a tree’s hardiness.
You can buy water-soluble organic potassium sulfate online or in local stores. Trees can also suffer from phosphorus, magnesium, manganese, molybdenum and boron deficiencies. Use superphosphate or bone meal for phosphorus deficiency, Epsom salts for magnesium, chelated iron and manganese treatments for manganese, and fritted trace elements for molybdenum and boron.
Local arborists recommend feeding your trees up to Sept. 5 in an early fall year like this one, with humates, neem oil, fish and kelp concentrates, and horticultural molasses. You can also make compost tea, which makes it easy to spread nutrients around your garden as a liquid or foliar spray. By giving your trees the attention they need, you can strengthen their immune systems and give them a better chance against pests and diseases.
I am a senior at Taos High School, a member of the Taos Tree Board, and an intern at the Taos Land Trust.
Information for this article was taken from the Royal Horticultural Society, Home Composting Made Easy, “Drought Damage to Trees” by Dr. Kim Coder at the University of Georgia, “Gardening in New Mexico” by John Cretti, “Is it Possible to Grow Your Plan’s Immune System?” by Amir Tajer, and “Holistic Core Values” by Michael Phillips from the Holistic Orchard Network.