Effectiveness, Costs, and Feasibility
Cooke et al. (1986) have listed the advantages and disadvantages of har-
vesting for managing nuisance aquatic vegetation.
(1) Most harvesting is not regulated by laws, nor is there a
waiting period for water
(2) Nutrients and organic matter are removed.
(3) Harvesting may facilitate other treatments, such as grass carp
or herbivorous insectintroductions.
(4) Little impact occurs to nontarget areas.
(5) Costs compare favorably
herbicides in the midwestern
United States, but not in southern areas where there are dense
infestations of exotic plants such as waterhyacinth
Harvesting is labor intensive.
Relatively small areas can be treated per day.
Fragmentation and spread of nuisance plants may occur.
Harvesting and unloading sites may be separated by great
Operating depths are limited.
Favorable weather is needed.
High initial capital costs occur, and there may be substantial
downtime for repairs.
Possible problems of access may occur.
Harvesting is of limited applicability when the growing season
is long, regrowth rates high, and infestations very dense'.
The effectiveness of harvesting in producing control of vegetation
appears to be related to the number of harvests per season, when harvesting
occurs, the types of plants present, the amount of vegetation per unit
area, and how the machine is used.
Most reservoirs are too large to obtain
complete control of nuisance vegetation by harvesting.
harvesting has to be planned.
Harvesters can be used effectively in more
restricted areas such as marinas, swimming areas, docks, and water intakes, if
a machine of proper size is used.
(1972) compared the effectiveness of single and mul-
tiple harvests in controlling biomass and next-season regrowth of Eurasian