Fielding Questions: Houseplant disease, mealybug control, apple trees not bearing
This week, gardening columnist Don Kinzler fields questions about brown spots on a houseplant's foliage, how to control mealy bugs, and if an apple tree should be replanted elsewhere.
Q: Our houseplant has problems on the older leaves. We water with dehumidifier water, rainwater or melted snow. The leaf tips turn brown and the leaves are dying. It was in its pot for about a year in Miracle Gro potting mix, and we recently repotted the plant again into a larger container and added fertilizer. The new growth seems healthy, but the problems continue. Can it be saved? – Paul N.
A: The plant looks like one of the many Dracaena species. From the circular brown spots on leaves and the yellow-green mottling on some of the foliage, I suspect a bacterial disease. Unfortunately, such diseases are internal to the plant, and there isn't a remedy.
You could cut off infected leaves and see if newer growth continues to develop normally. Otherwise, disposing of the plant might be the only option. With the good care you’re giving it, it’s had every opportunity to thrive.
I might suggest a few thoughts, though, about fertilizing. When plants are suffering, it can be tempting to do so, but fertilizer isn’t medicine for ailing plants, unless a nutrient deficiency is diagnosed. Until other ailments are corrected, plants can be stressed further by adding too many nutrients.
Q: I need help combating mealybugs on my houseplants. I’ve thrown away quite a few plants that don’t seem to be reacting to the sprays, granules or rubbing alcohol I’ve applied. Can you share insight on how to win the battle? – Elaine F.
A: Mealybugs can be very difficult to control when their populations explode, and I’ve thrown out dozens of plants as well. Control is difficult because the insects cover themselves with a powdery, cottony wax that protects them from insecticides.
Mealybugs barely move, if at all, and can be found at rest underneath leaves, on stems, and even on the outside of pots. They damage plants by sucking sap, and their feeding results in yellowing leaves, stunted growth, dieback and eventual plant death.
Attacking the first few mealybugs is the key, before they populate the plants with eggs that balloon into an uncontrollable situation. Systemic houseplant granules should be combined with insecticidal sprays or alcohol, and insects must be thoroughly saturated to penetrate the waxy coating. Repeat applications religiously at the intervals indicated on the product label.
Q: My dad passed away four summers ago, and as a gift from friends I received four apple trees about four feet tall. The varieties were from a local garden center and were types suited to our area. The trees have never produced apples and have gotten maybe two feet taller. Can I move these to another area on my farm this spring? – Robin S.
A: Unless there’s an important reason for moving the apple trees, such as being in shade, I’d hesitate to move trees that have been in place for four years. The stress of moving the trees will further delay fruiting, and will disrupt the root system that’s developed.
It’s normal for apple trees to take five to seven years before bearing fruit, and that’s good. It allows the tree to develop a strong, energetic structure capable of yielding successful future crops for years to come.
Apple trees will sometimes begin bearing a few apples prematurely in two or three years, but that’s often at the expense of the tree’s long-term health. Commercial orchards usually remove any apples that form for the first three to four years, while fruits are dime-sized.
So there’s nothing unusual about your trees not fruiting during the first four years. It sounds, though, that they’re only growing about six inches per year, which is less than normal. A vigorous young apple tree should be growing at least 12 to 18 inches a year.
To increase the rate of growth, add a circle of shredded wood product around each tree in the 5-5-5 rule, which means placing the shredded bark five inched thick in a circle five feet in diameter, kept five inches away from the tree trunk. If grass is allowed to grow up to the trunks of young, developing trees, the greedy grass robs moisture and nutrients, and easily cuts tree growth in half.
If you have a gardening or lawn care question, email Don Kinzler, NDSU Extension-Cass County, at firstname.lastname@example.org . Questions with broad appeal may be published, so please include your name, city and state for appropriate advice.