By Syed Tajdar Hussain
Dodder is a root less obligate stem holoparasite that lack of chlorophyll. Dodder extracts water nutrients and carbon predominantly from the phloem of its host via haustorial connections.
Historically, in the Gilgit Baltistan dodder has a single host that is Alfa alfa. This parasite used to attack the species and reach to it climax at the first harvest of Alfa alfa. In shina language it is known as Mayoun shain and in Burushiski it is called Tolay-phos, meaning the garden of golden oriale and the slough of snake respectively.
In the month of June the Chukar used to make a nest under the dense cluster of dodder, and the Alfa alfa and lay its egg in it. The children of surrounding villages who used to catch the chicks of Chukar(Aletoris chukar) search all these clusters found in Alfa alfa fields normally located at the foot hills. The impact of this parasite on Alfa alfa (a most common animal feed plant of the Gilgit Baltisan) remain unnoticeable and neither the farmers knew its damaging role to its host plants. The situation was common all over the Gilgit Baltistan where Alfa alfa used to be grown and every Alfa alfa field had invariably many clusters of dodder noticeable from a distance apparently from its yellow color clusters found dotted in a field.
The attack of dodder has become common and attacking many other species during the last decade. It is now spread all over the Gilgit Baltistan, and mostly attacking the species the people grow as vegetable in there gardens. It is an epidemic pest plant and likely to attack the cereal spp; if not controlled. The causes of spread of this pest are said to be the Alfaalfa seeds imported from China by some NGOs The magnitude of the attack is very high and has reached to the extend that in some villages the vegetable gardens have completely being ruined. The control and eradication of this pest has become unavoidable in view of its spreading nature and inflecting serious financial loss to the farmers. It is widely distributed as destructive parasitic weed plant in the Gilgit Balistan. It has long register of hosts, belonging to various plants families. The most common among the host include alfalfa, clovers, onion, potatoes, linseed, sugar beet, cucurbits, legumes and warm seed (artimsia spp). Hedges and ornamental plants are also attacked. Dodder retards the growth and reduces the yield of infested plants. The losses range from slight to complete destruction of some crops raised from dodder-contaminated seeds.
This parasitic weed plant may also serves as a bridge for the transmission of viruses from infested to healthy plants. In the beginning the infection is localized with the development of the small thread- like structures of orange to yellow color. They rapidly grow in size and density attacking healthy parts as well as the adjacent plants ultimately strangling the stem and above ground parts with dense tangle of leafless strands. In later stages each infested spots may cover 3-4m.Thus the dodder-infested areas appear as patches the field. With the spread of infection, several infested patches develop and combine giving rise to large areas covered with yellow coloured vines. Dodder perpetuates from year to year either through seed mixed with those of crops or infested crops debris containing seeds or living bits of vine. Under favorable condition either the seed germinates or plants bits initiate growth. If the germinating seeds or the plant bit does not find any host plant, they die away. Otherwise they develop contact with the hosts establishing parasitism through haustoria (feeding organs) and start growing. Sometime the dodder seed are also dropped by birds, eating dodder fruits, in the excreta on the growing plants. With time the germinating dodder plant loses it contact with the soil and starts depending entirely on the host plants water and nutrients supply. It continues to grow, spread and invade the host plant as well as develops flowers producing seeds.
The various species of dodder are so similar that a single description of its general character will suffice. When a dodder first evident in the field it will be noted as a tangle of branches thread like leafless stem devoid of chlorophyll, or green pigment twining around the stem or other parts of its host, forming an interlacing mat. The hostaria penetrate in to the host cortex and serve for the absorption of both crude material and elaborated food. The established dodder plant has no connection with the soil, but derives its entire supply of nourishment directly from its host and stored up in the seeds. When a support is reached weather it is congenial host or not the young stem begins to twin around it, if the supported structure is susceptible host, the young stem soon form haustoria which penetrate in to the host tissues and infection is accomplished, from now for a young seedling there is abundant of food is available so that the lower part of the seedling may discontent with the soil. A single plant has been reported to produce as many as 3000 seeds under favorable condition of moisture and temperature; seed germinate and produce young seedling dodder plant. The white, pink and yellow flowers occur in cluster appearing from early June until the end of growing season.
The use of dodder free planting seeds has long been a primary means of preventing the spread of dodder infestation. Once an area is known to be infested, it must be managed to prevent the further production of the dodder seed. Clean and remove them by hand before seed is produced. Spray herbicides to prevent seed production. Practical methods of preventing dodder infestation would be devised based on the use of clean and healthy crops seed, dispersal of crop reindues, eradication of other host weeds, possible restriction on the movement of animals and farm equipment from infested to healthy fields and rotation of crops. Some species of Smicronyx (weevils) reported as predator from Pakistan. Planting non-host plants can be affective means of managing a dodder infestation.