Randall K. Stocker

Predicting invasive plants in Florida using the Australian weed risk assessment.

Abstract Screening tools that effectively predict which nonnative species are likely to become invasive are necessary because of the disproportionate ecological and economic costs associated with invaders. We tested the effectiveness of the Australian Weed Risk Assessment system (WRA) in distinguishing plant species that are major invaders, minor invaders, and noninvaders in Florida. The test included 158 annuals and perennials in six growth forms from 52 families in 27 orders. The WRA with a secondary screen met all hypothesized accuracy levels: it correctly rejected 92% of test species that have been documented to be invasive in Florida and correctly accepted 73% of the noninvaders. The incorrect rejection of noninvaders was 8% with the remaining 19% of noninvaders falling into the “evaluate further” outcome. Only 10% of the 158 species required further evaluation. Invaders of natural areas and agricultural systems were identified with equal accuracy. Receiver operating characteristic analysis demonstrated high separation of invaders from noninvaders. The degree to which the WRA is precautionary may be adjusted by altering the cutoff scores that define the “accept, evaluate further,” and “reject” outcomes. This approach could be adopted in Florida as a screening mechanism to reduce importation of new invaders.

The Management of Invasive Plants in the United States: Are Scientists Providing What Managers Need?1

Abstract The link between science and management of invasive plants in natural areas appears to be the strongest at the “field crew” level, with historically high levels of research on control materials and methods, survey techniques, and monitoring strategies, and with a high rate of incorporation of science into field practices. Less scientific support is given to higher level managers, for example, those managing a whole ecosystem while attempting to determine invasive weed priorities. Although whole-ecosystem management concepts (e.g., adaptive management, integrated pest management) may be supported individually by a great deal of field research and careful thought, scientists have not conducted the experimental studies necessary to compare outcomes and provide practical means of implementation. In other words, the “science of management” in readily implementable form has not reached the upper levels of resource managers. The link between science and management may be the weakest where decisions are made about the amount of funding to allocate to the many competing parts of what should be a complementary management program, including public education, economic and ecological impact studies to document actual effects, early detection, and rapid response, and many others. Additional index words: Economic and ecological justification, public education, science-based management, terminology.

Residual effects of herbicide-treatedEichhornia crassipesused as a soil amendment

The use of Eichhornia crassipes (Mart.) Solms (water hyacinth) as a soil amendment in fruit and vegetable production has been proposed in several areas of the world. To assess possible residual effects, E. crassipes was treated with maximum label rates of diquat, glyphosate, and 2,4-dichlorophenoxyacetic acid (2,4-D) herbicides. Placement Experiment:E. crassipes was shredded into a fine mulch 1/2 hour, and 1, 2, and 7 days after herbicide or water (control) treatment (DAT) and added to soil in pots as a top mulch, a layered mulch, or a mixture, with seedling Lycopersicon esculentum (Mill; tomato) as assay species. Negative effects of glyphosate and 2,4-D were noted for L. esculentum growth only for the mixed treatment, and only at 2 DAT. Duration Experiment: coarsely chopped herbicide-treated E. crassipes was thoroughly mixed with soil. Reductions in L. esculentum plant biomass, including mortality, persisted for 1 DAT with diquat, 7 DAT with 2,4-D, and 14 DAT with glyphosate. Ratio/Soil Type Experiment: one day after herbicide application to E. crassipes, L. esculentum seedlings were planted into ratios (4:0, 3:1, 2:2, 1:3, 0:4) of herbicide-treated to untreated E. crassipes, and mixed with clay, loam, or sand. Glyphosate and 2,4-D reduced L. esculentum growth in proportion to the ratio of treated to untreated E. crassipes. Soil type did not influence herbicide effects on L. esculentum growth.

Residual effects of herbicide-treated Eichhornia crassipes used as a soil amendment

The use of Eichhornia crassipes (Mart.) Solms (water hyacinth) as a soil amendment in fruit and vegetable production has been proposed in several areas of the world. To assess possible residual effects, E. crassipes was treated with maximum label rates of diquat, glyphosate, and 2,4-dichlorophenoxyacetic acid (2,4-D) herbicides. Placement Experiment: E. crassipes was shredded into a fine mulch 1/2 hour, and 1, 2, and 7 days after herbicide or water (control) treatment (DAT) and added to soil in pots as a top mulch, a layered mulch, or a mixture, with seedling Lycopersicon esculentum (Mill; tomato) as assay species. Negative effects of glyphosate and 2,4-D were noted for L. esculentum growth only for the mixed treatment, and only at 2 DAT. Duration Experiment: coarsely chopped herbicide-treated E. crassipes was thoroughly mixed with soil. Reductions in L. esculentum plant biomass, including mortality, persisted for 1 DAT with diquat, 7 DAT with 2,4-D, and 14 DAT with glyphosate. Ratio/Soil Type Experiment: one day after herbicide application to E. crassipes, L. esculentum seedlings were planted into ratios (4:0, 3:1, 2:2, 1:3, 0:4) of herbicide-treated to untreated E. crassipes,and mixed with clay, loam, or sand. Glyphosate and 2,4-D reduced L. esculentum growth in proportion to the ratio of treated to untreated E. crassipes. Soil type did not influence herbicide effects on L. esculentum growth.