Phanerogamic plant parasites
- 1. Parasitic plant: The plants which produce flower and subsequently bear seeds in fruits and parasitized on other plants known as phanerogamic plant parasites. Haustorium: It is a specialized projection / root like branch or organ of a parasite that penetrates the host tissues and absorbs nutrients and water from the host cells. Phanerogamic parasitic plants
- 2. Phanerogamic parasitic plants Stem parasite Root parasite Holoparasites (Entirely dependent) e.g. Dodder on garden ornamentals and hedge plants. Semi-parasites (Partially dependent) e. g. Loranthus on fruits, wasteland, roadside and forest trees. Holoparasites (Entirely dependent) e.g. Orobanche on tobacco, mustard, brinjal, tomato, cabbage, cauliflower, turnip and many other solanaceous and cruciferous plants Semi-parasites (Partially dependent) e.g. Striga on sugarcane, cereals, maize and millets etc. Classification of phanerogamic parasitic plants:
- 3. Parasitric plant: Dodder (Love-vine, Amarbel) Scientific name: Cuscuta spp. Dodder: Dodder are the holoparasitic plants of jujibee, mango, some ornamentals and crop plants. Dodder are non-chlorophyll bearing, leafless, twining parasitic seed plants which attach their yellow, orange or pink thread-like stems to the stems or other parts of the cultivated or wild plants. They may be single but are mostly conspicuous as tangled mass of intertwining stems.
- 4. Overwintering and Dissemination The dodder seeds, overwinter in infested fields or mixed with seeds of the crop plants. The seeds may remain viable until a favourable season returns. Portions of stem are also resistant to adverse weather. The parasite may be introduced into a field and spread by any of the following means: • As impurity of the crop seed. • As seeds and stem pieces moved by irrigation water. • As stem pieces present on the dry straw from infested fields. • As seeds in the manure. • As stem pieces transported by cattle and farm implements. • As stem pieces carried by birds or strong winds.
- 5. Symptoms on host plants: 1.Host suffers from malnutrition 2.Vitality of the host plant is reduced 3.Plant may be dwarf 4.Yellowing of the leaves with less flowers and fruiting 5.In case of severe attack, the whole plant of the affected part may die.
- 6. A. Dodder stems entwined around stems of sunflower and potato (B). C. Dodder entwined around and overcoming a pepper plant.
- 7. D. Dodder covering and overcoming all watermelon plants in an area of a field. E. Dodder of the Lauraceae species Cassythia filiformis spreading over roadside shrubs and trees in Florida.
- 8. Disease cycle of dodder (Cuscuta sp.) on a plant such as alfalfa
- 9. Systematic position: Class : Dicotyledonae Order : Solanales Family : Cuscutaceae Genus : Cuscuta Species : Cuscuta gronovii
- 10. Control: Dodder can be controlled effectively by preventing its introduction into a field by the- 1. Use of dodder free seed 2. Cleaning agricultural implements before moving it from dodder infested field to new areas. 1. Limiting movement of domestic animals 2. Using of dodder free manure 3. Restricting the flow of irrigation water 4. Following a five year crop rotation with a non-host crop 5. Avoiding the dodder infested cattle fodder.
- 11. 1. Destruction of the crop by burning before seeding. 2. Chemical control by spraying herbicide like chemicals e.g. 2, 4-D, PCP (pentachlorophenol) @ 0.3-0.4% 8. Cutting or burning of patches, will kill both dodder and host plants but prevent dodder from spreading and from producing seed.
- 12. Common name: Mistletoes/Banda Scientific name: Loranthus sp/Dendrophthae sp. Description: Mistletoes are angiospermic semi-parasitic plant of fruit and forest tree. In our country mango trees are the worst sufferers from this parasitic. The parasite found on the tree as a dense cluster of twigs and bears smooth green leaves and tubular flower. It has no root system but develop haustoria into the host and intimate association with vascular tissues. The green leaves posses chlorophyll and synthesized carbohydrates. It depends on the host only for water and minerals but do not totally depend on host.
- 14. A. Male (yellow) and female (with fruit or seed capsules) dwarf mistletoe plants growing on a pine branch. B. Dwarf mistletoe plant parasitizing the trunk of a conifer (larch) and causing it to swell and, later, to possibly break at the point of infection. infections.
- 15. A. A Douglas-fir tree the top branches and trunk of which have been killed by dwarf mistletoe
- 18. Overwintering and dissemination: The parasite overwinters as seeds. The parasite is spread by dispersal of its seed mostly through birds and to some extent by other animals. The birds are attracted by brilliant colour of the fruit. Droppings of birds containing seeds also help in dissemination of the parasite.
- 19. Symptoms on host plant: 1.Stunted growth of the host 2.Reduce the leaves size and may show unhealthy green colour. 3.Flowering and fruiting may be hampered. 4.Tumour may form on the infected area. 5.Quality and yield of fruit is considerably lowered.
- 20. Control: 1.Physical removal of the parasite by pruning of the infected branches or by cutting and removing entire infected trees. 2.Detaching the parasite from the host in early stages of growth without damaging any parts of the host. 3.If tumour is one side of the branch then the wood just below the tumour may be sawed off. 4.Injection of copper sulphate sodium (25%) or 2-4, D (0.3-0.4%) into the affected branches have been found effective on many hosts. 5.Spray 30-40% diesel oil emulsion in soap water has been found effective in eradicating the parasite from mango.
- 21. Systematic position: Class : Dicotyledonae Order : Solanales Family : Loranthaceae Genus : Loranthus/Dendropthae Species : Loranthus sp. / D. falcata
- 22. Parasitic plant: Broom-rape Scientific name: Orobanche spp. Broom rape: Broom-rape (Orobanche spp.) are total root parasites affecting tobacco, mustard, tomato, cabbage, cauliflower, turnip and many other solanaceous and cruciferous plants, which are especially destructive to tobacco. Description of broom-rape: The parasite (Broom-rape) consists of a stout, fleshy, stem, 10-15 inches long. The stem is pale yellow or brownish red in colour and is covered by small thin and brown scaly leaves. Flowers appearing in the axil of leaves are white and tubular. The seeds are very small and black in colour and may remain viable in the soil for several years.
- 23. Broomrapes (Orobanche sp.) parasitizing various plants: A. On fava bean B. On broad bean. C. Orobanche parasitizing the respective plants and destroying the crop in a tomato field
- 25. Orobanche parasitizing the respective plants and destroying the crop D. In a carrot field and E. In a broadbean field
- 26. 2 1 Overwintering and Dissemination: The parasite overwinters as seed in the 1 inches depth of soil. Dissemination of seeds are carried out by rain water, birds and even animals. Development of parasitic relationship with host: Broom-rape overwinters in the soil of the infested field. During the growing season, the seed germinates and produces parasitic nourishment from there. A large number of parasitic roots may be seen breaking the soil around the host plants. When the host is carefully uprooted, the parasitic roots are seen interwined with the host root system. Symptoms on host plant: 1. Growth stunted, malnutrition and dwarfness of the host 2. Flowering and fruiting reduced 3. Sometimes the host plant died
- 27. Systematic position: Class : Dicotyledon Order: Orchidales Family : Orobanche Genus : Orobanche Species : Orobanche ramosa
- 28. Control: 1. Preventing the introduction of its seeds in new areas. 2.Planting non-susceptible crops in infested fields 3. Frequent weeding and removal of broomrapes before they produce new seed. 4. Long crop rotation with non-host crops may be practiced. 5. Drying the soil for six months may help to eliminate the parasite completely by reducing the soil population of the seeds. 6. Spraying the soil with 25% copper sulphate solution found to be successful in destroying the parasite.
- 29. Common name: Witchweed Scientific name: Striga spp. Losses: Losses vary and may range from slight to 100% Description: Striga is a semi-root parasite of mostly monocots such as corn, sorghum, millet, upland rice, and sugarcane, but also cowpeas, peanuts, other legumes, sweet potato, and tobacco and wholly dependent on the host from germination to flowering and reproduction. The parasite is a small plant, 15-30 cm tall, with bright green, slightly hairy stem and leaves. Usually these plants develop in clusters around the stem of the host. The parasitic stem appears branched, leaves are narrow , long, and in opposite pairs. The flowers are small and usually brick red or scarlet although sometimes may be yellowish red, yellowish or almost white. Flowers appears just above the leaf attachment to stem and are produced throughout the season. Seeds are formed in pods or capsules, each containing thousands of tiny brown seeds.
- 30. Overwintering and dissemination The parasites survives through seeds which require a minimum dormancy of 15-18 months. The short distance dissemination of the parasite takes place by the seeds through rain and irrigation water while floods and strong winds are the chief agents of long distance dispersal of the seeds. The parasite is also disseminated by contaminated tools and equipment and by contaminated soils carried on farm machinery.
- 31. A. Witchweed plant in bloom parasitizing a corn plant. B. Groups of witchweed plants parasitizing each corn plant along a row in a field Witchweed (Striga sp.) parasitizing plants
- 32. C. Corn plants parasitized by witchweed plants appear stressed, wilted, and stop growing. D. A different species of Striga parasitizing the legume plant hairy indigo.
- 33. Disease cycle of witchweed (Striga asiatica) on corn
- 34. Symptoms Affected plants remain stunted, wilt and turn yellowish. Death may follow these symptoms if the plants are heavily parasitized. Infected roots bear a large number of witch weed haustoria which are attached to roots and feed on it. One to several witchweed plants may be growing above ground next to the infected plants.
- 35. Control 1.Weeding and intercultural operation can be successful only when parasitized in early stages of the parasitic growth. 2. Keeping the field flooded for sometime and then draining out the water also helps in control of the parasite. 3. Catch crops consisting of host plants may be planted to force the germination of witchweed seed and, and the parasite can be destroyed by ploughing or by the use of weedicides such as 2,4-D. 4. Trap crops, consisting mostly non-host legumes, may be used to stimulate seed germination to destroy the Striga. 5. Field should be kept clean from weed host plants.
- 36. 4. Use of resistant cultivars, seed treatment with herbicides of differential toxicity, and use of witchweed- infecting fungi as a biological control are possible control methods under investigation. 5. Soil drenching with 2-3% copper sulphate solution up to a depth of 10-15cm can be done to control witchweed. 6. Soil fumigation with methyl bromide @ 0.01% is effective against Striga spp.