Presentation on theme: "What is a pest? Biological Pests are organisms that reduce availability, quality, or value of resources to humans. Whether something is a pest, depends."— Presentation transcript:
What is a pest? Biological Pests are organisms that reduce availability, quality, or value of resources to humans. Whether something is a pest, depends on one’s perspective.
Large swarms of mosquitoes can be very annoying to us, and also pose a risk for disease, but they are an important food source for many organisms.
Large animals can become pests also, I took a class in college called vertebrate pests. Examples: snakes, sharks, horses, elk, and bears. We realize now that these are important animals in ecosystems, but problems sometimes occur when humans and these animals interact.
Pesticide: chemical that kills a pest Biocide: kills all living organisms, don’t like these!!! Narrow agents that focus on killing a specific organism Fungicide Herbicide Insecticide
Humans have been controlling pests for thousand of years, but the modern era really got underway in 1934 with the discovery of the insecticidal properties of DDT. DDT is one heck of a pesticide; cheap, stable, and easily spread, is highly toxic to insects but relatively non-toxic to mammals.
Facts: 90% of all pesticides are used in agriculture and food storage and shipping. Developed nations use ~80% In developing countries the rate of increase is 7 to8% and in more developed 2-4%
Pesticide Types: Inorganic: broad spectrum, highly toxic, persistent, usually compounds of arsenic, copper, and mercury. Natural Organic: Also refer to as botanicals usually derived from natural plant compounds
Chlorinated hydrocarbons: DDT PDB are synthetic organic insecticides. Organophosphates: parathion malathion an outgrowth of nerve gas research from WWII
Microbial agents and biological controls: living organisms which help kill pests. These are used often in integrated pest management plans Lady Bugs!!!
Benefits: Disease Control: About 500 million people suffer from malaria at any given time. 2 million die each year. It is estimated spraying for mosquitoes has prevented 50 million deaths over the last 50 years from malaria.
Diseases such as encephalitis, bubonic plague, sleeping sickness, and river blindness can all be reduced by use of pesticides.
Crop Protection: Reliable data is hard to obtain, but some believe plant diseases, insect, bird, and weed competition can reduce yields by 1/3.
Post Harvest can be as great as 20-30% from rodents, fungi etc. Some cases the damage caused by insects or fungal disease is mainly cosmetic, and this reduces the economic value of the crop.
Problems: Effect on non-target species: estimates reach as high as 90% of pesticides never reach their target, and many beneficial organisms can be harmed.
Pesticide Resistance: evolution in action. Those organisms most resistant and able to survive the chemical treatment survive and pass their traits onto the next generation. Thus, the next generation is harder to kill with the same pesticide.
In addition most pests reproduced rapidly and produce many offspring, thus a pesticide resistant population can be quickly established. This phenomenon is called pest resurgence. Thus it may take more pesticides (increasing the dose) or more toxic pesticides to control the pest.
Creation of New Pests: By killing many organisms that are not pests, sometimes beneficial predators are also killed. New pests emerge, because their natural predator that kept their numbers in check, has been killed letting their population explode.
Canete Valley in Peru DDT used on Boll Weevils, DDT resistant Boll Weevils appeared. Toxaphene replaced DDT, but eventually became ineffective. Heliothis worms began replicating rapidly and became a problem. The wasps which had helped keep both organisms in check had been decimated by the use of the pesticides.
Persitance and Mobility in the Environment: DDT and other pesticides are often quite stable and do not break down easily in the environment. The build up in the food chain and can be transferred far from areas where they were initially used.
Examples: Minnesota and Iowa 20 to 30% community and 30-60% private wells had detectable pesticide residues. Long range transport can occur as pesticides can move by rain and snow. Example Isle Royale in Lake Superior.
Human Health Problems: Short term effects include acute poisoning and illness caused by relatively high doses and accidental exposures.
Long term effects suspected to include cancer birth defects immunological problems. Long term effects may be caused by very low doses of a variety of different chemicals, and are very difficult to tie to a specific source.
Who? Farm workers who handpick fruit and vegetables (often migrant workers) are most effected both short and long term by pesticide exposure. Improper storage at home leads to 20,000 Americans getting sick each year.
Alternatives to Current Pesticide Uses: Behavorial: crop rotation, mechanical cultivation, habitat diversification (windbreaks ground cover, hedgerows) which provide habitat for natural predators, reduction of herbicide use etc.
Biological Controls: Predators (wasps and ladybugs) pathogens (bacteria Bt and viruses) Certain birds Herbivorous Insects: Australia, prickly pear cactus introduced, escaped gardens became prevalent in the wild, a natural predator from South America the cactoblastis moth helped combat the problem and has ate much of the cactus.
Genetics and Bioengineering: release of sterile males into population interferes with reproduction. Production of crop varieties that produce natural insecticides, so that chemical spraying is not necessary.
IPM: Integrated Pest Management Combines many techniques to control pests. Pesticides still may be used as part of the overall plan, it is only one tool used to control them.
Timing pesticide application so one dose with a non-persistent chemical is used. Use of trap crops (planted earlier than main crop, pests are attracted to this crop, then it is destroyed with pests, leaving the main crop much less exposed to pesticides).
Successful IPM’s MA – A group of apple growers have reduced pesticide use by 43% while maintaining crop yields equal to those using normal practices. Indonesia – In 1986 banned 56 of 57 pesticides in current use. Crash course of IPM to train farmers. Reduced pesticide costs by 75% and had higher yields than their neighbors using normal practices.
Regulating Pesticides 3 agencies; EPA, FDA, and Dept. of Agriculture EPA regulates use and sale of pesticides under the Federal Insecticide, Fungicide, and Rodenticide Act. The FDA and Dept.Ag. Enforce pesticide use and tolerance levels set by the EPA.
Delaney Clause In 1958 this clause was added to the FFDCA prohibiting the addition of any known cancer causing agent to processed foods, drugs, or cosmetics. This is a zero risk policy, and additives in use before 1954 were considered safe. Also pesticides registered after 1978 were subject to Delaney while those before had less stringent standards. Thus you could drink all the coffee you wanted, but food processors could not add a drop of coffee to their product.
This is Insanity! So in… 1996 it was amended with the standard of reasonable certainty of no harm, defined as no more than one case of cancer for every million people over a lifetime. Even this can be exceeded if a particular chemical would adversely affect consumers or disrupt the food supply.
Complete Review Questions 1-5 for homework! Quiz over lecture and homework material questions.
Thus, the next generation is harder to kill with the same pesticide.