Takecallis species Aphids do little damage in small numbers. They are extremely prolific, however, and populations can rapidly build up to damaging numbers during the growing season. Damage occurs when the aphid sucks the juices from the bamboo leaves. The aphid is unable to digest fully all the sugar in the sap, and it excretes the excess in a fluid called honeydew. The honeydew often drops onto the leaves below. A sooty mold fungus may develop on the honeydew, causing the bamboo leaves to appear black and dirty; or rain may wash the honeydew off before the fungus has a chance to grow. Ants feed on honeydew and are often present where there is an aphid infestation.
Spray with a garden insecticide labeled for bamboo aphids, or use an insecticidal soap when aphids first appear. Direct the spray to the undersides of leaves. Repeat the spray in summer if the plant becomes reinfested. Avoid over-fertilizing, which enhances aphid populations.
Some types of bamboo flower heavily at periods of 10 to more than 100 years, then die or almost die. The time of flowering seems to be genetically-rather than environmentally-controlled. Plants of the same species sometimes flower at the same time all over the world. Giant timber bamboo (Phyllostachys bambusoides) and other large bamboos seem most prone to this type of flowering. Other bamboos flower less vigorously, then recover their strength after flowering. Flowering and dying might occur in a single year or might take several years.
Flowering cannot be cured, and nothing can stop it, including removing the stalks as they flower. Removing the flowering stalks may make the plants more attractive, however. Plants may recover slowly, or new plants may grow from suckers or seeds. This may take several years, however. Water and fertilize plants well during this period to hasten recovery. If you cannot wait to see if the plants will recover, dig them up and replace them with another bamboo species.
Schizotetranychus celarius This mite feeds only on bamboo and a few related grasses. Probably accidentally imported from Japan, where it is native, it is now on the West Coast and in Florida. Like other mites, bamboo mites cause damage by sucking sap from the undersides of leaves. As a result of this feeding, the chlorophyll disappears, causing the yellowed appearance. A severe mite infestation weakens the plant and makes it unattractive. Bamboo mites make a small pad of webbing that protects them as they feed. Other types of mites also feed on bamboo, but they make a loose sheet of webbing that covers whole leaves and move about actively on the webbing. Other mites also cause a generally stippled appearance rather than the parallel bands caused by the bamboo mite.
Because bamboo mites are not yet widespread, you may be able to eradicate them. If the infestation is severe, cut all bamboo to the ground and burn the canes and debris, or bag them for removal. Watch for signs of the mites as bamboo grows back. The mites generally enter a yard on purchased bamboo plants. Keep new bamboo isolated for a few weeks and look for signs of infestation.
Several different types of scales infest bamboo. In spring to midsummer the young scales, called crawlers, settle on leaves and stems. The small 1/10 inch), soft-bodied young feed by inserting their mouthparts and sucking sap from the plant. The legs usually atrophy, and a hard crusty or waxy shell develops over the body. Mature female scales lay their eggs underneath their shells. Some species of scales that infest bamboo are unable to digest fully all the sugar in the plant sap, and they excrete the excess in a fluid called honeydew, which often drops onto the leaves below. A sooty mold fungus may develop on the honeydew, causing the bamboo leaves and stems to appear black and dirty. An uncontrolled infestation of scales may kill the plant after two or three seasons.
Spray with an insecticidal soap or an insecticided labeled for bamboo scales in late spring when the young are active. Or spray with a horticultural oil to kill the adults, and hose down the plants the following day.