What is wrong with my horse chestnut?

are there any large cankers formed on the major roots and trunk and may extend up the trunk?

Are there any reddish or dull brown, irregular blotches concentrated at the tips and margins of infected leaflets?

Are the leaves small, discolored, and drop early, clusters of honey-colored mushrooms may sprout at the base of the plant?

Are some of the leaves of your chestnut skeletonized?

Are there any yellow caterpillars with clumps of white hair on their backs?

Are there any circular white spots visible on trunks or large branches?

Bleeding canker is caused by Phytophthora fungus. The fungus enters wounds and succulent roots. Well-defined cankers have reddish-brown margins. Reddish-brown sap oozes from the cankers. Eventually, new leaves remain small and yellow and branches begin to die. Remove the infected tree and do not replace it until the soil has been fumigated and aerated thoroughly.

Guignardia leaf blotch is a fungal disease that attacks horse chestnuts. Caused by the fungus Guignardia aesculi, the disease produces reddish or dull brown, irregular blotches that are often concentrated at the tips and margins of infected leaflets. The blotches are often outlined by a conspicuous yellow band. To protect your tree clean up and destroy fallen leaves to remove overwintering spores, cut all affected leaves, and destroy them.

Armillaria root rot is a fungal disease that cannot be effectively controlled once it has become established. Diseased or dead plants should be uprooted and removed. Planting resistant rootstocks is the most effective method of preventing the disease.

Whitemarked tussock moths feed on leaves and leave only nervature uneaten. Control their numbers by scraping off and destroying patches of their eggs when you see them. With serious infestations, you'll have to use insecticides to deal with these caterpillars.

Japanese beetles feed on chestnut leaves and leave only veins uneaten. They are half an inch long metallic blue-green insects. You can knock beetles off of leaves into jars filled with soapy water.

Horse chestnut scale (Pulvinaria regalis) are seen as circular white spots visible on trunks or large branches (and sometimes mistaken for pigeon droppings). Scrape off minor infestations with your fingernail. Prune out badly infested growth, or use a soft brush and soapy water to gently scrub the scales off the stems. Control scales by spraying insecticidal oil during the growing season.

If there are wandering, white or translucent tunnels in leaves the culprits are Horse chestnut leafminers (Cameraria ohridella). These tiny white, maggotlike larvae feed inside leaves. Prune off and destroy all infested leaves. Cover plants with row cover until flowers open to prevent adults from laying eggs on plants. Certain nematodes can attack leafminer larvae inside leaf tunnels.