Biocontrol agents against eichhornia crassipes
crassipes grows in shallow temporary ponds, wetlands and marshes, sluggish flowing waters, lakes, reservoirs and rivers (Batcher Undated). Water hyacinth now flourishes in all continents but Europe (Lindsey and Hirt 1999, in Williams Undated) where it does exist but doesn't flourish as a result of climatic conditions. The coat has 12-15 longitudinal ridges (Gopal 1987, in Batcher Undated). Mature seeds can number 450 per capsule, are 4 x 1mm, with an oval base and tapering apex. The fruit is a thin-walled capsule enclosed in a relatively thick-walled hypanthium developed from the perianth tube. Anthers are violet and measure 1.4-2.2mm long (Gopal 1987, in Batcher Undated). Three are small and close to the perianth tube. There are six stamens (sometimes 5 or 7) having curved filaments with glandular hairs. When young, this labellum has a green spot. The posterior tepal (labellum) has a central bright yellow diamond-shaped region surrounded by a deep blue border with bright red radiating lines. Tepals are ovate to oblong, thin, lilac and up to 4cm long. The perianth tube is 1.5-1.75cm long with a green base and pale top. Each spike has 4-25 flowers (maximum 35) with 8-15 being the most common. They are dark violet to bluish or pinkish violet (though whitish if grown in total darkness) and contain soluble pigments, including anthocyanins that may protect the root from herbivory (Gopal 1987, in Batcher Undated).\r\nįlowers are borne terminally on a lavender spike on an elongated peduncle and are subtended by two bracts. As many as 70 lateral roots percm give the roots a feathery appearance. Roots are adventitious and fibrous, 10-300cm in length. They may be elongated, swollen in the middle and tapering towards the blade or they may form a bulbous float (Gopal 1987, in Batcher Undated) containing air-filled lacunate tissue (Sculthorpe 1985, in Batcher Undated).\r\nĪs much as 50% of a single water hyacinth’s biomass can be roots. Petioles are spongy and measure up to 5cm in diameter and 30-50cm in length (maximum 125cm). The petiole bears a large membranous stipule, which forms a sheath around the next younger leaf. Each leaf consists of a petiole, isthmus (between petiole and blade) and blade. Foliage leaves are petiolate with a glossy sheen, and are arranged spirally, appearing to be in a rosette. Leaves form as the axillary bud grows, rupturing a tubular leaf-like structure called a \"prophyll.\" As the internode between the first leaf and the prophyll elongates, roots are produced at the node bearing the primary leaf. Stolons are purplish violet and extend up to 50cm or more in length and are highly variable in diameter (Gopal 1987, in Batcher Undated).\r\n Plants on the edge of a mat form stolon buds while those in the middle may not. Axillary buds, which can also form stolons, grow at an angle of 60 degrees from the rhizome and remain at that angle or bend upward in dense stands, or become horizontal in open stands. Crassipes forms a shoot consisting of a branched, stoloniferous rhizome, 6cm in diameter and up to 30cm in length, with several short internodes. Its roots are purplish black and feathery (Gopal 1987, in Batcher Undated).\r\nĮ. The flowers have six petals, purplish blue or lavender to pinkish, the uppermost petal with a yellow, blue-bordered central splotch. The stalk is erect, to 50cm long, and carries at the top a single spike of 8-15 showy flowers. Leaf veins are dense, numerous, fine and longitudinal. They are broadly ovate to circular, 10-20cm in diameter, with gently incurved, often undulate sides. Its leaves are thick, waxy, rounded, and glossy and rise well above the water surface on stalks. crassipes is a free-floating aquatic macrophyte growing generally to 0.5m in height but to nearly 1 metre in height in some southeast Asian locations (Gopal 1987, in Batcher Undated).