Question: I’m sorry to bug you again, but I can’t think of anyone else to ask. When I have been going out in the backyard, in the dirt there are dozens of tiny craters. They are perfect, about an inch deep, and inch wide, and perfectly circular. Something is making them in the night, what can it be?
Answer: The craters are like tiny pitfall traps and each contains a doodlebug at the bottom under the sand. They are supposedly called doodlebugs because of the way they doodle in the sand while they meander about. They are young antlions, a kind of predatory insect of the family Myrmeleontidae. If you know your ancient Greek, the translation is easy (myrme = ant, leon = lion). They sit in the bottom of the cone shaped hole waiting for unsuspecting ants to fall in and then they eat them. Interestingly, these insects make their cone shaped traps using the steepest angle the sand can maintain that shape so that the slightest disturbance will cause the prey and the sand to fall to the bottom where the antlion waits, jaws up, for supper. It can be cheap entertainment for kids if they like to manually put ants into the holes and watch the carnage. That’s what we did. Caution: playing with insects is habit forming and they might grow to be entomologists like me.
Q: I am concerned about an evergreen tree in our pool area. I don’t know what it is called. It has a whorl of glossy green leaves on each branch and small flowers that smell like orange. The base is about 5 feet from the pool deck. We are concerned about roots growing and breaking through. Can you advise?
A: It is called Pittosporum tobira or Japanese mock orange. It is a slow growing shrub that requires weekly irrigation, does well in moderate sun or light shade, and grows to be 6 to 8 feet tall on average. It is a common plant around Tucson as well as Japan. It should not be a problem for your pool.
Q: We received a lovely Ficus benjamina in April. Of course, when we brought it home it dropped many leaves. Just as that was almost over some of the leaves quickly turned brown, staying on the stems, on one side. There are no signs of insects or spots on the leaves. The first couple of weeks it probably did not get enough water, we were told every two weeks. Then after searching on the web we discovered it needs watering when the surface is dry, about weekly or less in Tucson. It has been watered weekly for three weeks now. It gets sprayed daily. Both water and spray contain small amounts of Miracle-Gro indoor plant food, not the recommended amount. The brown leaves/branches are spreading to the rest of the plant. It is not dropping many leaves now. Should the branches with dead leaves be cut back?
A: The leaf drop is an indicator of stress and could be related to the environment: water, light, and temperature. The leaf browning may be a function of salt burn from excess built up in soil in your container. Repotting with fresh soil or a good soaking with high quality water should help remove or wash the salt through the soil. Then you can resume watering to keep the soil moist as you were. It’s also a good idea to put it outside in the sun if you can. Ficus trees need more light than a lot of other “house plants.”
Q: What are these little gray buggers on my sunflower leaves?
A: They are lace bugs, small plant bugs that suck plant sap from the leaves. They are often found on the underside of leaves. The grayish ones are the adults and the smaller, blackish ones are the nymphs. The smallest black spots are their frass (poop). On sunflowers, we just let them be because they might damage the leaves but the flowers are unaffected and the plants seem to tolerate them to some extent. Other plants are not as tolerant. If you wanted an organic solution you could try insecticidal soap, horticultural oil, or a pyrethroid such as PyGanic.
Peter L. Warren is the urban horticulture agent for the Pima County Cooperative Extension and the University of Arizona. Questions may be emailed firstname.lastname@example.org