Keywords: Invasive species Ecosystem function Insect pests Invasive plants Ecological restoration Biological control Natural ecosystems a b s t r a c tOf the 70 cases of classical biological control for the protection of nature found in our review, there were fewer projects against insect targets (21) than against invasive plants (49), in part, because many insect biological control projects were carried out against agricultural pests, while nearly all projects against plants targeted invasive plants in natural ecosystems. Of 21 insect projects, 81% (17) provided benefits to protection of biodiversity, while 48% (10) protected products harvested from natural systems, and 5% (1) preserved ecosystem services, with many projects contributing to more than one goal. In contrast, of the 49 projects against invasive plants, 98% (48) provided benefits to protection of biodiversity, while 47% (23) protected products, and 25% (12) preserved ecosystem services, again with many projects contributing to several goals. We classified projects into complete control (pest generally no longer important), partial control (control in some areas but not others), and ''in progress," for projects in development for which outcomes do not yet exist. For insects, of the 21 projects discussed, 62% (13) achieved complete control of the target pest, 19% (4) provided partial control, and 43% (9) are still in progress. By comparison, of the 49 invasive plant projects considered, 27% (13) achieved complete control, while 33% (16) provided partial control, and 49% (24) are still in progress. For both categories of pests, some projects' success ratings were scored twice when results varied by region. We found approximately twice as many projects directed against invasive plants than insects and that protection of biodiversity was the most frequent benefit of both insect and plant projects. Ecosystem service protection was provided in the fewest cases by either insect or plant biological control agents, but was more likely to be provided by projects directed against invasive plants, likely because of the strong effects plants exert on landscapes. Rates of complete success appeared to be higher for insect than plant targets (62% vs 27%), perhaps because most often herbivores gradually weaken, rather than outright kill, their hosts, which is not the case for natural enemies directed against pest insects. For both insect and plant biological control, nearly half of all projects reviewed were listed as currently in progress, suggesting that the use of biological control for the protection of wildlands is currently very active.

/ We hypothesized that repeated herbicidal (maintenance) control of water hyacinth infestations in Florida suppressed biological control agent populations, especially the weevils Neochetina eichhorniae and N. bruchi. We therefore sampled water hyacinth and weevil populations at 54 sites distributed statewide. Half were under maintenance control, half were not treated with herbicides. General site conditions were assessed, demographic data were collected on weevil and plant populations, the reproductive condition of the weevils was determined, and plant nutrient and proximate composition of water hyacinth leaves were analyzed. Water hyacinth infestations under maintenance control were minimal when compared to unmanaged sites. Likewise, on a population basis, all weevil cohorts were much lower due to the paucity of plants. Plants at unmanaged sites, where weevil intensities were much higher, suffered high levels of stress and showed low growth potential. Lower percentages of the female weevils were reproductive at unmanaged sites when compared to managed sites, so densities of reproductives and immatures were similar at both site types. Reproductive status of the weevils improved with increased plant quality. Plant quality, in turn, declined as stresses arising from weevil feeding increased. Plant quality was positively correlated with plant growth potential and flower production. Thus, maintenance control improved plant nutritive quality thereby inducing reproductive vigor of the weevils, but ensuring plant regrowth and the need for future control. This suggests that biological and herbicidal controls should be integrated, using herbicides to maintain water hyacinth infestations below management thresholds but in a manner that conserves biological control agent populations. This approach would lead to improved plant nutritional quality that would, in turn, stimulate reproduction in biological control agent populations. KEY WORDS: Eichhornia crassipes; Neochetina eichhorniae; Neochetina bruchi; Phytophagy; Integrated control; Aquatic weeds

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