Observation on Parthenium phyllody. Parthenium is believed to have been introduced to Ethiopia during the Ethio-Somali border conflict as a cover for smuggled arms around 1977 GC. Now it is reported from all over the country. The current estimate of infested area in the country is about 120,000 hectares of land of which the share of grazing, crop and other lands is 40%, 32% and 28% respectively. Parthenium has now come to be a national problem. A Control and Regulation Task Force has been set up at the federal, regional, zonal and district level to mobilize the community for a continued control campaign in the rural and urban areas. The task force is composed of the various sector offices and administration councils, at the respective level of administration. The major control practice exercised at present is hand pulling and subsequent burning. However, spite of the repeated control campaigns by the community by the community, the problem is getting worse over the years. Not to mention a reduction in infestation level, even prevention of further spread does seem easy to come by. Provided the weed occurrence in uninhabited and less accessible areas which in most cases may not belong to any one in particular, it is difficult to expect hand pulling to cope with the problem. Neither we have another simple and effective control method at hand. Fortunately nature itself seem to have enough of Parthenium to hire one of its agents to see that its population is reduced. A Parthenium Phyllody, a relentless disease assumed to have been caused by a Phytoplasma like organism (PLO) has been observed working fast with a brutal efficiency in rendering infected Parthenium plants completely without seed. Typical symptoms of the killer disease include.
The fast rate of increase in level of infestation of the disease from one or two plants to be found after searching the entire locality in Kobbo area, North wollow zone, and Kombolcha area, South wollo zone in 1999 GC to be so conspicuous to miss in 2000 GC has been considered to be a consolation to the helpless victims of the menace. The phenomenon has also raised our hope for use in biological control for such a rapid spread on necessity transmission must have a simple mechanism. Insect vectors like aphids and leafhoppers are potential candidates. Attempts to inoculate artificially by rubbing healthy plants with the diseased and direct injection with filtered and centrifuged suspension prepared by crushing diseased plants in water have been tried. Although no symptom has been noted so far follow up continues. Symptom development was reported to take 40 to 50 days after inoculation (4). It is also known that mechanical transmission of PLOs has not yet been achieved (2). However, a fried egg like appearance claimed to be a typical feature of PLO in cell freemedia (1) was obtained from infected stem splits plated on to a saboroid agar in our laboratory. Aphids had been found on infected Parthenium plants during our survey last summer, 1999 GC. However, although the incidence of the disease has increased this year, proportional increase was not observed in association of aphids with the diseased plants. However, an intensive search reinitiated later has come up with other potential agents. A leafhopper other sucking insects have been collected by sweep netting diseased Parthenium plants in the field. Artificial inoculation of healthy lants grown in polyethene tube with the help of these vectors has been planned. Currently the Parthenium biocontrol worldwide seem to concentrate on insect and fungal agents only. Although some work is underway on the rust fungus Puccinia abrupta var. parthenicola in this country, its importance as a potential bioagent particularly for the northern part of the country is not reliable as it appears so late in October after the end of the rainy season when Parthenium is abundant. Incedently October is one of the coldmonths in Ethiopia which is favourable for the rust fungus (3). As neither the rust fungus is as common and devastating to Parthenium as the phyllody disease nor there are other promising agents we believe much emphasis be given to the latter at least until it is proved to be impossible or too expensive or risky to employ. With some research work before hand we believe the leafhopper could be used for biocontrol purpose. Reference
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