Gadenin日本語Get the appThe good news, and the real risks
Compared with apples, plums or peaches, persimmons are close to trouble free. There is no equivalent of codling moth waiting for you, the leaves are tough and largely ignored by chewing insects, and most gardens will never need to spray the tree at all. If you came to persimmon from other tree fruit, you can put down most of your habits.
What does go wrong is mostly not a pest. In order of how much fruit they actually cost people, the persimmon grower's real problems are fruit drop, limbs splitting under the crop, birds, and sunscald on exposed bark and fruit. Diagnose in that order before you start looking for insects.
The habit worth building is a slow walk round the tree once a fortnight through the growing season. Look at the undersides of leaves on a few shoots, look at the junctions where large limbs meet the trunk, and look at the ground for dropped fruit. Two minutes a fortnight catches everything on this tree in time to do something about it.
Fruit on the ground is a disorder, not a pest
Before you blame anything living, work out which drop you are seeing. A heavy shed of marble-sized fruit a few weeks after bloom is the tree self-thinning, and it needs no response at all. Larger fruit falling later is a stress response, and the cause is almost always water: a dry period followed by a heavy soak, which the tree reads as a shock.
Excess nitrogen produces the same result, so a tree that is dropping fruit while carrying long soft shoots and unusually dark leaves has been overfed. Root disturbance, from digging or from a path being laid over the root zone, does it too, and the fruit falls weeks after the digging so the connection is easy to miss.
Cut open a few of the fallen fruit before deciding. Clean flesh with no tunnel and no insect means a drop caused by conditions. A tunnel, a grub or a rotten core means something else and you should identify it, but on persimmon that is genuinely uncommon.
Fruit that splits at the calyx end, usually late in the season, is a watering problem: dryness during sizing followed by heavy water as the fruit ripens. Even out the moisture and mulch; split fruit cannot be saved and rots quickly.
What actually shows up, and what to do
The short list below covers nearly everything a home persimmon grower will meet. Most of these are controlled by pruning for airflow, clearing fallen fruit and leaves, and encouraging the predators that deal with scale and mealybug on their own. Reach for a spray only when you have identified the problem and it is doing measurable damage.
| Problem | What you see | When | What to do |
|---|---|---|---|
| Scale insects | Small raised brown or white bumps on twigs, sticky leaves, sooty black mold | Noticed in summer, established earlier | Scrub off light infestations; prune out badly encrusted twigs; horticultural oil while dormant |
| Mealybug | White cottony masses under the calyx and in branch crotches | Late summer, worse in dry years | Dislodge with a jet of water; open the canopy so predators can work |
| Anthracnose and leaf spot | Dark sunken spots on leaves and fruit, early leaf drop | Wet summers | Rake up and remove fallen leaves and fruit; thin the canopy for airflow |
| Crown and root rot | Whole tree wilts and declines, bark dark at the base | Any time, after wet spells | Not curable. Prevention is drainage; never mulch against the trunk |
| Birds | Pecked holes in coloring fruit, whole fruit gone | As fruit colors | Net the tree, or pick astringent fruit at full color and ripen indoors |
| Deer and larger animals | Browsed shoots, stripped low fruit, rubbed bark | Autumn and winter | Physical fencing or trunk guards; nothing else works reliably |
| Sunscald | Cracked, sunken, dead bark on the south or west side of the trunk | Hot summers, worse after heavy pruning | Shade the trunk or paint it with dilute white latex; never over-thin the canopy |
| Wasps and ants | Feeding on already damaged or split fruit | At ripening | They are secondary. Remove split and pecked fruit promptly |
Split limbs are the biggest single loss
Persimmon wood is brittle in a way that surprises people. It does not bend under a load and spring back; it fails suddenly, with a crack, and the split usually runs down into the trunk from a narrow crotch. It nearly always happens in the last few weeks before harvest, when the fruit is heaviest, and often in wind or after rain has added weight to the leaves.
The damage is not just the lost fruit. A split that tears down the trunk leaves a long wound that does not seal, and it opens the tree to rot for the rest of its life. This is the failure most likely to shorten your tree's life, and it is entirely preventable.
Prevention is three things done at the right time. Build a frame of wide-angled scaffold limbs while the tree is young and remove narrow crotches before they get large. Thin the crop after the early drop, taking the outermost fruit off long limbs where the leverage is greatest. And prop any limb that has started to bend, using a padded fork, well before the fruit is at full weight.
If a limb does break, cut it back cleanly to the collar of the nearest sound branch or to the trunk as soon as you notice. Leaving a torn stub is far worse than removing the limb. Do not attempt to bind or bolt a split back together on a tree this brittle; it will not hold.
Leaves that look wrong
Yellowing between the veins while the veins themselves stay green, worst on the youngest leaves at the shoot tips, is iron shortage. On persimmon this is nearly always caused by soil that is too wet or too alkaline for the roots to take iron up, rather than by a lack of iron in the ground. Improve drainage first and treat the leaves as a symptom of the soil.
Whole leaves yellowing evenly and dropping in midsummer, starting at the bottom of the tree, usually means the roots are short of air or water. Check the soil twelve inches (30 cm) down before assuming disease.
Bear in mind that persimmon leaves color brilliantly and drop early in autumn, well before the fruit is ripe. A tree covered in orange fruit on bare wood is behaving exactly as it should. Every year somebody treats that as a disease.
The record that pays off
Note the date you first see any problem, where on the tree it was, and how much fruit was on the tree that year. Persimmon problems are strongly seasonal and strongly tied to crop load, and a single year of observation tells you almost nothing.
The entries worth the effort are: the date the early fruit drop began and how heavy it was, the date and cause of any later drop, any limb that broke and where the split started, and the date of the first bird damage. Three years of that turns a vague sense that the tree is unreliable into a clear picture of which years are heavy, which limbs are weak and when to get the netting out. It also stops you spraying for an insect problem you do not have, which on this tree is the most common wasted effort of all.