CENTER TD, JUBINSKY GP, GRODOWITZ MJ
US Department of Agriculture Agricultural Research Service Aquatic Plant Control Research 3205 College Ave. Fort Lauderdale, Florida 33314, USA
Environ Manage. 1999 Feb;23(2):241-256. doi: 10.1007/s002679900183.
/ 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
我们推测，在佛罗里达州对凤眼蓝侵扰进行反复的除草（维护）控制会抑制生物防治剂种群，尤其是象鼻虫类的水葫芦象甲（Neochetina eichhorniae）和南美水葫芦象甲（N. bruchi）。因此，我们在全州分布的54个地点对凤眼蓝和象鼻虫种群进行了采样。一半地点处于维护控制之下，另一半未使用除草剂处理。评估了一般的场地条件，收集了象鼻虫和植物种群的人口统计学数据，确定了象鼻虫的繁殖状况，并分析了凤眼蓝叶片的植物养分和近似成分。与未管理的地点相比，处于维护控制下的凤眼蓝侵扰程度极低。同样，从种群角度来看，由于植物数量稀少，所有象鼻虫种群数量都低得多。在象鼻虫密度高得多的未管理地点，植物承受着高水平的压力，生长潜力较低。与管理地点相比，未管理地点的雌性象鼻虫繁殖比例较低，因此两种地点类型的繁殖象鼻虫和未成熟象鼻虫的密度相似。象鼻虫的繁殖状况随着植物质量的提高而改善。反过来，随着象鼻虫取食引起的压力增加，植物质量下降。植物质量与植物生长潜力和花的产量呈正相关。因此，维护控制提高了植物的营养质量，从而诱导了象鼻虫的繁殖活力，但要确保植物重新生长以及未来控制的必要性。这表明生物防治和除草控制应结合起来使用，使用除草剂将凤眼蓝侵扰维持在管理阈值以下，但要以保护生物防治剂种群的方式进行。这种方法将提高植物营养质量，进而刺激生物防治剂种群的繁殖。关键词：凤眼莲；水葫芦象甲；南美水葫芦象甲；植食性；综合防治；水生杂草
