Q. I liked your article about fruit trees in the newspaper. This year was difficult. An arborist suggested the citrus leaf miner traps mentioned above and they work very well. I replace them every 3 months and catch a lot of bugs. No pesticides are needed and the trees are infection free.
A. I've received several emails about leaf miners so I had to include them in my leaf miners column.
These pheromone traps can be found at farm stores or online after some research (I've never seen them in our local stores). They are safer and easier to use than ground drenchers as they only affect problem insects, not bees. I'm glad to hear that they are easier for their owners to find.
There are other versions of eco-friendly sticky traps, too, including apple-hugging butterfly traps. Many of them look like small pyramids or origami houses, with a small entrance hole just big enough for the target insect. Pheromones are species-specific, so only one species of insect will be attracted to the trap. Once inside, you can't get out.
Other sticky traps, such as mouse or rat traps, should never be used outdoors. Being non-specific, they may catch non-target wildlife such as lizards, frogs, skunks, and mice or birds.
Q. The directions for my Bonide Systemic Granules state that they should not be used on vegetables or other foods. Can you explain or clarify why you recommend citrus?
A. There are very few systemic insecticides approved for use on crops such as fruit trees. These are marked as such. Most systems are not approved for edible/vegetable crops.
It is very important to follow label directions carefully when using these or any other pesticide. Most systematic plants can only be used for a very short time, usually after the flowers have fallen and not too close to harvest. Treatment after the flowers have faded protects bees and other nectar feeders. Early treatment offers an opportunity to remove the pesticide before the fruit is harvested.
Q. My 30 year old magnolia has lost a lot of leaves and many of the upper branches are bare. We tried adding more water but it didn't help. No offers?
A. Since you didn't mention any other symptoms or signs (such as the presence of insects, crawling crabs, cobwebs, or fungi), my first guess would be bacterial leaf blight. Affected trees look like they need watering, but don't improve with more watering. It is caused by a bacterium that invades the plant's vascular system and prevents water from reaching the leaves. Leaf rot begins at the tips and progresses up the branch.
The bacterium is spread by the Glasswing Sniper. On heavily infected trees, sticky droplets fall from the leaves — these are sniper droppings.
Unfortunately, there is no effective treatment for bacterial leaf blight. Sometimes dead branches can be cut off, but if the infection has spread throughout the tree, it will likely die.
Are you looking for more gardening tips? This is how you can reach the master gardener program in your area.
Los Angeles District
mglosangeleshelpline@ucdavis.edu; 626-586-1988; http://celosangeles.ucanr.edu/UC_Master_Gardener_Program/
Orange County
ucceocmghotline@ucanr.edu; 949-809-9760; http://mgorange.ucanr.edu/
county on the river
anrmgriverside@ucanr.edu; 951-683-6491 East. 231; https://ucanr.edu/sites/RiversideMG/
County of San Bernardino
mgsanbern@ucanr.edu; 909-387-2182; http://mgsb.ucanr.edu/
