Several species of Phytophthora have been reported to be responsible for black stripe. The common species are: Phytophthora palmivora (Butl.) Butl., P. meadii Mc Rae, P. botryosa Chee.

In 1984, several other species of Phytophthora were identified as causes of black stripe infection in China : P. citrophthora (Smith & Smith) Leonian, P. cactorum (Lebert & Cohn) Schroeter, P. capsici Leonian

Distribution

The 1998 IRRDB survey shows that black stripe is a serious problem in Brazil, Cameroon, China, Côte d'Ivoire, India, Indonesia, Malaysia, Thailand, Vietnam. An earlier survey had indicated that China, Côte d'Ivoire and Sri Lanka have serious problems with black stripe. The severity of the disease was then lower in India, Malaysia and Thailand although it was an endemic problem in all these countries. In Brazil, Nigeria and Philippines the disease is generally sporadic and controllable, with occasional local, very severe outbreaks in Brazil. For results of 1998 Survey.

Symptoms

The early symptoms of black stripe are not obvious: a series of sunken and slightly discoloured areas just above the cut. Later, vertical fissures appear in the renewing bark; when these are removed, dark vertical lines are visible. As the infection progresses, the stripes coalesce forming broad lesions, finally spreading the full width of the panel. When the disease is severe, it extends vertically in the wood as far as 15cm below the tapping cut and 2-5cm upwards on the regenerating bark. Pads of coagulated latex sometimes form beneath the bark causing extensive bark splitting and bleeding.

Occasionally, infection occurs on untapped bark resulting in a wound, called "canker". This may arise on bark previously affected by black stripe or on wounds caused by spouts or wires. The early symptoms of canker are not obvious, but, in the more advanced stage, the bark bursts and latex oozes out. Pads of coagulated latex form under the bark causing it to bulge and split open.

Disease spread

Black stripe infections are associated with wet weather, being favoured by prolonged cool and rainy periods. The fungus is commonly present in the soil and spores are spread by water droplets. In areas where abnormal leaf fall occurs the spores are washed down from the canopy. Canker development is more common in leaf fall areas via heavy inoculum from the tree canopy.

Disease control

Black stripe can be kept under control during continuation of tapping by regular applications of an effective fungicide provided the disease is detected before infection becomes severe. The recommended fungicides are 0.8% a.i. captafol alternate daily or 0.2% metalaxyl once every four days. Recently 0.4% (oxadixyl + mancozeb), 0.4% a.i. (oxadixyl + propineb) and 0.8% a.i. (folpet + orfurace) applied two to three times weekly are recommended. The frequency of treatment can be reduced to once-a-week applications by incorporating these fungicides in 3% methyl cellulose. Usually the disease will come under control after 6-8 weeks' application.

Original Data Sheet April 1994