To care for a dying persimmon tree, you must first determine what is causing the decline. Before attempting to diagnose a pest or disease problem, ensure that your persimmon tree is getting full sunlight, monthly deep watering to supplement rainfall and annual pruning to thin out fruiting stems. Also make sure that you're feeding your persimmon tree no more than 1 pound of 10-10-10 NPK (Nitrogen-Phosphorous-Potassium) fertilizer per 1 inch of trunk diameter each year. Do not expose your persimmon tree to temperatures below 0 degrees Fahrenheit during dormancy or below 26 degrees during growth periods.
Get rid of whiteflies, thrips and fruit flies that may be causing your persimmon tree to die, attacking the fruits and sometimes the leaves or wood. Treat the persimmon with an appropriate insecticide if you see these pests attacking the tree and its fruits.
Help your dying persimmon tree by getting rid of flat-head borer infestations. If you see holes drilled into the bark with gum oozing out of them and an overall decline in the tree's health, apply an appropriate insecticide made for fruit tree borers.
Treat mealybugs and scale problems associated with ant infestations by applying an insecticidal spray designed for ants and safe for fruiting trees. Look for distorted and damaged young shoots on the persimmon tree, along with failing new growth, to diagnose these problems.
Treat mite infestations of your persimmon tree by applying an appropriate insecticide or miticide once per month after the flowers drop, following the dosage and application directions on the label. You'll know that your persimmon tree is infested with mites if you see a brown, lacy collar on the tree.
Treat anthracnose diseases and crown gall with applications of fungicides, such as a Bordeaux mixture. In late spring and early summer, look for dead spots on the persimmon's leaves, twig dieback, cankers on the small branches and an overall thinning of the canopy to diagnose anthracnose diseases.
Identify physiological problems causing the fruit to drop from your persimmon tree. Reduce your watering sessions and cut back on fertilization to correct this problem. Thin out the fruits in May or June so that only one or two fruits remain on each twig to relieve stress on the tree.