Q: My magnolia tree has been taken over by flies and wasps. There are half-inch pink bumps on the branches, and the leaves are turning black. Leaves are falling off the tree. What is wrong with the tree, and how can it be fixed?
A: Your magnolia has scale insects. They have a shell that looks like that of a turtle. Scale insects have sucking mouthparts to suck sap from branches. Infested branches are weakened, and growth slows. Severe infestations kill branches, and severe attacks can kill trees.
Due to the scale insects’ sugary droppings, the plant’s leaves and everything under the tree often become covered with sap. Other insects are attracted to the excreted sap. Sooty mold — a black fungus that grows on the sap — soon covers everything. Sooty mold impacts and cuts down photosynthesis because it blocks sunlight from the leaf. The leaves turn yellow and fall off, and the tree becomes weaker.
Young magnolia scales are shiny, pinkish brown and smooth, but they become covered with a white wax over time. This wax is lost at the time the crawler stage begins. In late August or early September, adult females give birth to live young called crawlers.
The crawlers are very tiny, flattened and vary in color, from yellow to reddish-brown. The crawlers settle on one- to two-year-old twigs to feed, and they remain there through the winter.
Insecticide sprays, such as insecticidal soap, can control crawlers. The adults covered in the scale are much harder to treat. I would use a garden hose to try to wash off as many adults as possible at this time. It will also wash some of the sap and sooty mold away, which will help get rid of the other insects.
Systemic insecticides containing either imidacloprid or dinotefuran can be used in late summer but will need some time to move through the plant. The adult’s scale shell will remain in place even after it is dead. This may give the impression the insecticides did not work. Dead adults will be dry and easy to pick off.
Q: My tomatoes have stopped turning red. They are just sitting there green. They aren’t growing in size, either. Any suggestions on getting them growing again?
A: The heat wave that swept the country is probably to blame. Tomato fruit doesn’t grow well when the temperature is over 95 degrees. They don’t pollinate very well either, so when the temperatures are too high, the flowers fall off and no fruit forms.
Nighttime temperatures above 75 degrees also inhibit tomato plants. Larger tomatoes are more affected by high temperatures than smaller, cherry tomato varieties. When the temperatures drop back into the low 80s during the day and low 70s at night, the plant will continue to grow and produce fruit. Keep the plants healthy by watering them when the temperatures are high.
Don’t forget that these are the temperatures the plant is experiencing — not the temperatures the thermometer in the shade is displaying or the weatherman on the radio is announcing.
A garden near a building that bounces sunlight and heat toward said garden may experience warmer temperatures.
If your garden is in a warm location, you can try one of the tomato varieties that does better in higher temperatures. Currently, these varieties only gain the gardener a few degrees of relief, and the plants will do better at the same temperatures as regular tomatoes. Next time you are looking for tomatoes and seeds, do a search for heat-set tomatoes. You will find several varieties, including some old heritage classics.
Email questions to Jeff Rugg at firstname.lastname@example.org.