Q: I have a plum tree with little holes in the leaves. This happened last summer and again this spring. Can you tell me again what the cause could be and how to treat it?
A: Plums, apricots and peaches all get a bacterial disease called “bacterial leaf spot.” It is also commonly called “shot hole disease,” because it looks like someone stood back and shot the leaves with a shotgun.
The disease spends the winter in the stems. During spring rains, it opens up lesions on the stems and splashes onto leaves, stems and fruit. On a leaf, the disease kills small areas of tissue which drop out, leaving a hole. If the infection is bad, it can kill the whole leaf. If the tree loses a lot of leaves, it will decline in vigor and other things may kill it, such as a very cold winter.
The infected fruit develops brown or black dots that eventually become pits and cracks. The fruit is still edible, but it will be unsightly.
The disease can be controlled by spraying a fungicide weekly in the spring, starting when the tree begins to leaf out. Use any fungicide that is labeled to treat bacterial leaf spot on plums, apricots or peaches.
Q: One of my hosta plants has holes in the leaves. What can I do? There are no yellow or brown areas around the holes to indicate a sickness.
A: Hosta leaves are a favorite food of slugs. Slugs are also a common pest (with their friends the snails) for many perennials and vegetables as well as some trees.
Slugs need to stay moist, so they hide in mulch and under logs, flowerpots and anything else that hasn’t moved in a while. They feed at night, so check your plants with a flashlight after dark. Slugs and snails are susceptible to any slug killer or bait available at a local nursery. Wet down the soil in the area before using the product so the slugs will be active that night.
Clean up the area around the infested plants by picking up any boards, logs, etc. and looking for the slugs. Use footed pots to elevate your garden flowerpots and saucers so the slugs have no moist place to hide.
An organic control is diatomaceous earth. Rake the mulch away from the base of the plants a few inches and sprinkle the powder around the base of the plant. It is made from tiny microscopic animals from the ocean called diatoms. They are shaped like snowflakes, and after they have died, they leave behind tiny sharp-pointed skeletons that the slugs will not glide over.
Slugs can also be lured to their death in bowls of beer. Set the bowl down into the soil so the edge is at ground level. This may not work if other animals drink the beer first. There is some research that has shown caffeine kills slugs, so you may want to try giving them coffee.
Q: My son sent me some Dutch tulip bulbs this past Mother’s Day, and the instructions were to keep them indoors until they bloomed. The leaves turned yellow, so I have now cut back the flower and stems to the dirt level. Can I plant the bulbs in the ground now, and how deep do I plant them? If I can’t plant them now, what do I do with them in the meantime?
A: Bulbs that have been forced to bloom in a pot usually do not bloom well when planted in the ground. Tulips are going dormant outside, and yours are dormant, too. So, you can plant them anytime between now and this fall. It would be best to keep them in a cool, dry location and wait to plant them in the fall. This way, they won’t start growing prematurely if the soil gets moist from rainfall. Plant them two to three times as deep as the bulb is tall.