Question
I live in Az. and my flowering plum tree has sap seeping from many ares on the trunk. I think something is boring into it but don't know how to stop it. Lost the same kind if tree last year, I was told to paint the trunk which i did but lost it anyway. Is there some kind of chemical I can put at the base or on the trunk to stop this? Linda

Answer
Sounds like the Peachtree Borer Synanthedon exitiosa (Say)

The peachtree borer is a major pest of peaches but sometimes causes serious damage to cultivated cherry, plum, apricot, nectarine and ornamental shrubs. The peachtree borer has been reported in al fruit-growing areas of the United States and Canada.

Injury or Damage

The principal damage is done by the larvae, which feed on the cambium, or growing tissue, and inner bark of the tree. Most of the larval activity is confined to the trunk area from a few inches above to 6 inches below the ground line. Larval feeding may completely girdle and kill young trees. Older trees are less likely to be girdled but are often so severely injured that their vitality is lowered so that other insects, diseases and environmental conditions can complete their destruction.

Borer-infested trees bleed or exude gum during the growing season. The frass of sawdustlike excrement in the exuded gum indicates the presence of borers. Trunk injury by diseases or environmental conditions will usually produce clear gum.

Peach tree borer is controlled in commercial orchards by insecticides that contain permethrin (Pounce, Ambush) or esfenvalerate (Asana). Insecticides containing these active ingredients (permethrin, esfenvalerate) are recently becoming available in some garden centers. Perhaps more widely available is carbaryl (Sevin). Some formulations of this insecticide allow use on fruit-bearing trees. A new insecticide is onyx which is sprayed on the lower trunk and absorbed into the trunbk killing the borer.

Other Controls
Paradichlorobenzene (PDB) moth crystals, used as a fumigant, may help control infestations of peach tree borer within a tree. After clearing away leaves and other debris from around the tree base, place the crystals in a band 1 to 2 inches from the base of the tree trunk. Cover the crystals with enough soil to create a 5- to 10-inch packed mound around the plant. The crystals release a gas at temperatures above 60 degrees F. The gas penetrates the trunk to kill peach tree borer larvae. Applications of PDB crystals are best made in late September or early fall but also can be applied in late spring.

PDB can injure plants. To avoid plant injury, follow these precautions:

1.Do not allow the crystals to touch the tree bark.
2.Adjust the amount of crystals used by tree size. Use 1/4 ounce on a first-year tree, 1/2 ounce on a 2-year-old tree, 3/4 ounce on a 3- to 5-year-old tree, and 1 to 2 ounces on a large, well-established tree.
3.Remove the soil mound three weeks after the application.
With some effort, many larvae can be dug out of the tree or killed by puncturing them with a strong, thin wire. Be careful with these methods because they may cause more mechanical injury to the tree than the borer itself.

Borers attack trees under stress so keep the tree growing healthy by fertilizing with 10-10-10 fertilizer at the rate of 1 lb of fertilizer per inch of trunk diameter scattered around the tree and watered in good, Also water the tree during dry spells.