[/center]PROBLEM: We continue to have problems with 14-inch Ficus standards. Branches defoliate, then die, leaving shriveled-up twigs that smell foul. Someone suggested that the problem might be Phomopsis. Our grower states that they never have this problem. What could it be? Kansas
SOLUTION: Your grower is probably correct, they never have this problem because they so generously give it to you, however often unknowingly. Phomopsis spp. causes diseases to more than a hundred different plant varieties, yet most notable is the seemingly never-ending problem associated with interior ficus. Healthy plants naturally resist diseases for several reasons. In the case of a healthy growing ficus, the tree can adequately heal open wounds, which is a common port of entry for diseases. A branch that is overcome by the pathogen is often hidden by the swarm of dense growth that normally occurs with ficus under production conditions.
Simply put, the more open wounds left behind by pruning, the greater the potential for the disease. Likewise, the ficus that suddenly is plunged into an acclimation period (no growth) is highly susceptible. Knowing how the Ficus benjamina is produced is helpful. Take your average 14-inch benjamina standard. The soon-to-be tree starts as a 24-inch to 36-inch air layer stuck into a 10-inch pot. The rooted branches are lined out pot to pot in the Florida sunshine. Thus, cut off from their mothers, they undergo some acclimation during a period that is their first risk of survival. Some die, yes from Phomopsis, yet most take hold and grow quite rapidly. Still others are produced from lab-rooted tissue culture plugs. Others end up directly in 14-inch pots. While the tissue culture plugs may wait a couple of weeks under shade cloth, they all end up outside in direct sun.
Approximately six months later, the 10-inch are bumped up into 14-inch and may be pruned. At this time, while not often noticeable, the trees are again susceptible to disease. The grower who chooses the open look with uniform upright branching, prunes up the trunk and sides. For those who insist on the "lollipop" look, the trees are buzzed with a gas-powered hedge trimmer (rummm rummm) to start that beach ball appearance. After another six months, the trees are brought into the shade. They're often pruned again and begin acclimation, another stage that leaves the trees susceptible to infection. This acclimation period should last for a minimum of eight weeks, although 12-plus weeks is better. Some growers believe the tree is at its best for interiors when acclimated under shade beyond 17 weeks.
As you can see, the multiple stages of ficus production expose the tree to several opportunities for diseases to take hold. Moreover, natural conditions may call for additional pruning stages. For example, larger specimens that await acclimation while growing in fields are often pruned back severely following freeze damage.
All this time, Phomopsis may exist on the trees, although suppressed and barely noticeable. As previously stated, open wounds and stress allow the disease to do its thing. Our luck, the next step stresses the poor tree, which is carrying more cuts than Frankenstein. That is, we bring it into the interior.
We try to teach out technicians to make surgically precise cuts with gleaming, clean, razor-sharp pruners; we don't issue hedge pruners. I'm not suggesting that the owner lose the hedge pruners and start pruning everything with hand pruners (all 500 of them). If we wanted this, we'd accept a dramatic price increase over the $17 to $24 tree.
Study your newly received trees closely. Active Phomopsis is typified by branch defoliation and die back. The bark sloughs off easily. Typical of the disorder is an ammonia, cat urine-like odor. Don't worry, you'll know when you smell it. Should you discover this with newly received trees, consider the material unacceptable. To find evidence of prior infections of Phomopsis, study the cuts left by old pruning. Invariably, you'll find stubs from 112 inch in length to whatever. Cut off that stub with an eye toward proper natural target pruning. Peel back some bark. If you find black, random lines under the bark against the wood, as if they had been drawn with a pen, you're looking at the dead masses of old stroma left behind by once-active Phomopsis. Likewise, the tree side of the cut should not be discolored.
The existence of such evidence does not mean the tree is unacceptable, unless your growers states so. I believe you'd never use another ficus if you used this as a criteria for acceptability. The fact is, now is the time to clean it up and stay vigilant. While the actual organism that causes the disease is fragile, conventional sprays cannot penetrate the bark to come in contact with Phomopsis. The closest thing that comes to a cure is increased light, which allows the tree to outgrow the disease.
I prefer a well-acclimated, open style tree, as opposed to the beach ball. The average indoor environment will not allow adequate light to penetrate deep into the foliage head, resulting in heavy defoliation. As such, the tree is stressed again.
The open-type style lends itself to light penetrations and simple pruning. The myriad of criss-crossed branches associated with the beach ball leaves you with the "where do I begin?" pruning question.
At this time, the ideal 14-inch Ficus benjamina is evading us. However, I'd look at recommendations that anyone might share.
INTERIORSCAPE Magazine
March/April 1994
