Plum

Plum pox (sharka)

What you will see

Chlorotic spots, bands or rings and vein clearing on leaves (best seen in spring). On fruit, chlorotic spots or rings; fruit may be deformed with browning of the flesh; on apricot stones often pale rings. Fruit drops prematurely.

The source says: yields can be severely affected, with premature fruit drop.

How to protect

1. Prevention

   • Plant only healthy certified (virus-free) saplings.
   • Choose tolerant or resistant varieties.
   • The virus is spread by aphids and by grafting/propagating from infected plants; most spread is within a few hundred meters of the source.
2. By handThere is no cure for the virus in orchards. Infected trees are removed (eradication), which lowers infection pressure.
3. Chemical — only when nothing else helpsAphid products and mineral oils have only limited effect (mainly in nurseries); a product authorized in your country against vectors (aphids) only if the other steps are not enough.

Brown rot

What you will see

Fruit rots brown with cream-coloured spore pustules, drops or dries up as mummified fruit on the tree. At flowering, blossoms and fruiting spurs turn brown and wilt (blossom wilt). Severity varies with the weather at flowering time.

The source says: stone fruits like this one are susceptible to brown rot.

How to protect

1. Prevention

   • Protect fruit from birds with netting – the fungi enter through wounds (from birds, codling moths, scab).
   • Mummified fruit touching the bark causes small cankers and releases spores in spring – do not leave it on the tree.
   • Plum varieties 'Czar', 'Jefferson', 'Ontario' and 'President' have partial resistance.
2. By hand from midsummerPick up rotten fruit straight away; bury it at least 11¾ in deep or put it in biowaste if your council accepts it.
3. By hand at flowering and in winter dormancyRemove affected fruiting spurs and blossoms by pruning where possible.

Plum aphids

What you will see

Curled leaves (leaf-curling plum aphid) or sticky honeydew (mealy plum aphid).

How to protect

1. Prevention

   • Tolerate most aphid outbreaks; yield and tree health usually do not suffer.
2. BiologicalEncourage natural enemies; pesticides are not recommended.
3. Gentle spray winter dormancyOil just before bud break (at the end of winter dormancy) against overwintering eggs.

Plum fruit moth (plum moth)

What you will see

Plums ripen early and are often slightly deformed; inside is a pink caterpillar with a brown head (up to ½ in) and brown frass near the stone. Entry hole ~⅛ in with a drop of resin.

How to protect

1. Prevention

   • Tolerate a small loss of fruit – usually only part of the crop is affected.
   • Encourage birds, badgers and ground beetles.
   • Pheromone traps hung in the tree in early May are for monitoring flight only (they do not kill the pest).
2. By hand from April, at the latest from early MayPheromone traps for monitoring; on isolated trees they may reduce mating. Collect infested fruit that has dropped early.
3. Biological September–OctoberSpray entomopathogenic nematodes onto the trunk, branches and soil under the tree after the caterpillars have left the fruit; they do not protect against moths from the surroundings and can affect non-target animals. In a garden, Trichogramma wasps (which parasitise the eggs) also help.
4. Gentle sprayBacillus thuringiensis gives only partial control of the caterpillars.
5. Chemical — only when nothing else helpsA product authorized in your country against plum fruit moth; use in gardens is essentially not recommended – the timing (usually around early July and early August) is set by the warning service.