Ligustrum or Ficus? Thrips Know
QUESTION: I have a ligustrum hedge. Lately, it is growing leaves that are green but curling. Some turn yellow and have spots as well. I have tried spraying to no effect. Could you give me some advice?
--G.I., Pacific Palisades
ANSWER: Usually, curling leaves indicate some kind of sucking insect, like aphids or thrips, which is surprising because privet, or Ligustrum japonicum, is one of the more bullet-proof plants. The dwarf Texas privet, L. japonicum, or ‘Texanum,’ is one of my favorite hedge or background plants, virtually trouble-free.
If it is one of the sucking insects, you’re going to have to catch the critter before the leaves curl. By then the damage is done and the pests have often moved on, have been controlled naturally by predators or are hiding inside the rolled leaves.
Many can be controlled easily with nonpoisonous measures, including horticultural soap or oil sprays. Follow directions carefully.
However, first make sure the plant is a ligustrum. The leaves of Ficus microcarpa nitida are very similar, and it is commonly used as a hedge because it grows so quickly (though it also gets rather large, needs frequent pruning and has invasive roots).
A quick way to tell the difference is to look at the leaf tip. The ligustrum has a pointed tip; the ficus also has a pointed tip, but the very end is blunt.
This ficus is frequently covered with curled leaves, especially at this time of year, caused by Cuban laurel thrips, a tiny sliver of a pest. There are often tiny black calluses on the leaves, and the thrips are hard to control because they hide inside the curled leaves, where most sprays can’t reach them.
If you can tolerate the disfiguring, the ficus will shrug off and outgrow the attack. It’s been suggested that the plants should be trimmed or sheared in winter and the infected leaves disposed of. This will get rid of most of thrips, which have a hard time surviving winter outside their blanket roll of leaves.
If you’re seeking a chemical control, Orthene may be the best bet because it is systemic.
Rodents Biting Holes in Drip-Tubing System
Q: There are many plants on a deck in my backyard that are watered by a drip system with standard one-quarter-inch tubing. I recently found that one supply line was leaking from many (more than a hundred) small bite holes that I assume to have been caused by mice or some other small rodent. Is this a common problem?
--R.W., Rancho Palos Verdes
A: I wouldn’t call it a common problem, but where rodents are present, they will gnaw on the tubing; it’s one of the drawbacks of drip. In this case it may be the work of the common roof rat, which can hear the water running inside the tubing and will bite through for a drink.
In the garden, the tubing can be buried (though gophers will puncture it if they are around), but on a deck, the lines are vulnerable to rodents.
You might try providing them with a bowl of water and hope that satisfies their craving or try covering the exposed tubing with wood tunnels or loose rock.
Better yet, suggests Robert Kourik, author of “Drip Irrigation for Every Landscape and Garden” (Metamorphic Press, [707] 874-2606; $15), use PVC irrigation pipe for all the supply lines, using only the small, soft tubing to supply the pots.
Ponds Require Work Only During Winter
Q: How much work is involved in the maintenance of a pond with a few goldfish and a minimum of plant life? My wife wants a pond but doesn’t want to spend hours maintaining the thing. Would you install an above-ground filter or not? We are not into koi.
--T.C., Los Angeles
A: For most of the year, few things in the garden are easier to care for than a pond. Building it is another story (a flexible liner will make installation easier), but you won’t need that filter you mentioned. Only ponds packed with koi need filters.
The plants act as natural filters (that’s why they’re part of the planned recycling system for the first manned trip to Mars) so you really don’t want a “minimum of plant life.” Seventy-five percent of the water’s surface should be covered by plants like water lilies. Lilies and other aquatic plants with floating leaves, including water snowflake or water poppy, are the easiest to care for because they grow at a reasonable rate.
Many aquatics, especially those called “bog plants,” such as water iris and azure pickerel, require more work because they grow so fast.
The work comes in winter, when the lilies must be repotted and other aquatics divided. Because they are grown in pots or tubs inside the pond--in ordinary clay soil--they must be lifted out, and they are very heavy and very messy.
Other than this big job, ponds pretty much take care of themselves if you have a balance of fish--such as the goldfish you mentioned--pond snails and plants.
And to answer another reader’s question: No, these pond snails are not the same kind that plague the garden. There are several kinds that can live only in water, and all are scavengers, eating decaying vegetation.
To Banish Ivy Roots, Use Shovel or Spray
Q: Could you tell me how to get rid of the roots of ivy? It threatened to swallow up the place before I paid to have two truckloads hauled away. Now it’s back.
--H.F., Ventura
A: Obviously the roots weren’t removed along with the tops. Algerian ivy is shallow-rooted, you should be able to remove most roots by digging down a few inches. They are tough, though, and there are lots of them, so this can be quite a job.
You can also spray the tops before the ivy is removed, or when the remaining roots sprout, with Roundup or Final, systemic herbicides that travel down to the roots inside the plant. If you follow the directions carefully, these will kill the roots; then they can be dug out so you can grow something else in the ivy’s place.
