BEsT MANAGEMENT PRACTICEs HANDbooK - Tahoe BMP

Pesticides can be degraded by sunlight, water, bacteria, and other chemicals.The ones which last the longest, called persistent pesticides, can move overlong distances and can build up in the environment leading to greater potentialfor adverse effects to occur. For instance, glyphosate, the active ingredient inRoundup, the most widely used herbicide in the United States, has a half-life of30 to 100 days. Generally, the pesticides that degrade most rapidly have lessopportunity to move or have adverse impacts on people or other organisms.The volatility of a compound will determine how long it can travel by air fromits source. Its solubility in water is a factor when the pesticide is carried off byrain or runoff to streams or the Lake, or moved through the soil as a potentialgroundwater contaminant. There are other important factors that governmovement, such as adsorption, which is the propensity of a chemicalcompound to bind to soil.From a general knowledge of these and other characteristics, it is possible topredict in a general sense how a pesticide will behave. But more preciseprediction is often not possible because the environment itself is very complex.There are large gaps in the knowledge of pesticide movement and fate in theenvironment, so to err on the side of human safety and the environment,measures to minimize unnecessary release of pesticides into the environment isTRPA policy.5.3.2.4 INVASIVE WEEDSInvasive weeds grow aggressively, spread rapidly, and choke out native andother desirable plants. Weeds compete with native vegetation for water,nutrients, and sunlight, especially during vegetation establishment. They tendto produce prolific amounts of seeds and thrive because they lack naturalpredators. Noxious weeds are a subset of invasive weeds that are particularlydestructive, competitive, and difficult to control. They are regulated inCalifornia and Nevada law and there are specific requirements for theircontrol. The Lake Tahoe Basin Weed Coordinating Group (LTWCG) providesmany resources that can help you identify weeds, prevent their spread, anddevelop appropriate management plans (see www.tahoeinvasiveweeds.org).According to the LTBWCG, the most effective, economical, and ecologicallysound method of managing invasive plants is to prevent their invasion in thefirst place. Most current infestations in the Lake Tahoe Basin are still small andcontrollable. Once weeds become established and widespread, considerableeffort and expense will likely be necessary to control them.Hand or mechanical methods are the best options for treating small-scaleinfestations of annual and biennial weeds. Loosen soil at the base of the weed inorder to remove the entire plant including seeds and roots. Dig out as much ofthe root as possible. If the weed has flowered and seeds may be present, bag itsecurely and dispose of it in the trash. Do not compost weeds as seeds may stillbe able to germinate despite the breakdown of organic material. Seeds canCHAPTER 5: Soil and Vegetation ManagementTRPA BMP HandbookPage 5-14 2012