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Pondweed
There are over 80 species of pondweed worldwide with many of them occurring in New Mexico. Identification of pondweeds can be tricky as the appearance of the same species can vary tremendously depending on growing conditions. Stems vary from upright to horizontal and from a few inches to several feet long. Pondweeds can spread by rhizomes (modified underground stems), winter buds, seeds, or fragmentation, depending on the species. All pondweeds have underwater leaves, scattered on long (up to 10 feet), flexible stems that are rooted to the bottom. Some species, such as American pondweed, have floating leaves, which usually have a different shape than the underwater leaves. Flowers of pondweed plants are usually greenish or brownish in color, small in size and grow in spikelets.
Most pondweeds are fairly beneficial in general. However, pondweed can quickly become a nuisance aquatic plant if not monitored or left untreated. The productivity of pondweed is remarkable. A single plant grown in cultivation produced over 63,000 fruits and 36,000 tubers over a 6-month period. This wildfire-like growth has been known to completely overtake small ponds with pondweed density noted from the top to bottom.
ACI biologists recommend controlling pondweed with a single application of a systemic, root killing herbicide during late spring. Supplemental treatments may be required through the rest of the growing season depending on water quality, temperature, and density of growth. Ideally, obtaining control of pondweed growth early in the season is the best technique lake managers use to keep pondweed growth at healthy levels. This will ensure that growth density does not exceed treatable levels during the summer months when growth is typically accelerated. Another popular control method used in conjunction with chemical treatments is the use of grass carp. This technique has proven very effective in controlling unwanted pondweed growth when constant monitoring and treatment is not an option for some managers.
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