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What is the effect of pesticides on worm growth?

What is the effect of pesticides on worm growth?



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As a new semester begins, we were asked to propose ideas for investigatory projects. Our idea revolves around the effects of pesticides on non-target organisms. Since frequent use of pesticides may potentially affect the health of the soil, we chose the earthworms as our target organism. Our experimental set-up was revolves around studying their growth. Two containers (Container A-Control, Container B-Experimental) would be filled with soil and other things that are essential for worms to live. In container A, normal soil would be used. On container B, we would spray pesticide on the soil and mix them so that it really gets in the soil. After that, we would place the worms (5 each container). The allotted time for data gathering and analysis is 3 weeks. Given this situation, we would observe the behavior of the worm each day for 10 to 14 days (depending on our schedule) and their growth on the last day by measuring their length, weight, and describing their color.

I think that our set-up is logical instead of finding farms that sprayed pesticide for the last 20 or so years which is difficult in our situation. Does anyone have any feedback on the particulars of the experiment based on previous research on the subject?


Terbuthylazine and carbofuran effects on growth and reproduction within three generations of Eisenia andrei (Oligochaeta)

Sublethal effects of terbuthylazine and carbofuran on the growth and reproduction of Eisenia andrei were investigated over a period of three generations. Reproduction was assessed by measuring the coccon production of worms treated chronically with pesticides. Inhibition of cocoon production was found in the parental generation. Hatchlings were raised from cocoons to provide the F1 generation. During raising a more rapid growth of juveniles treated with terbuthylazine was observed, compared with the growth of untreated worms. The increase in vitality was also found in cocoon production. Groups treated with terbuthylazine produced more cocoons than controls. The F2 generation was raised from hatchlings of the F1 generation, and here, also the terbuthylazine treatments increased earthworm growth, but not cocoon production. Exposure to carbofuran decreased cocoon production in all generations. Growth of the F1 generation was not influenced by low concentrations of carbofuran.

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Insecticides

Insecticides are chemicals used to kill insects and some other arthropods (mites, ticks, spiders, etc.) or to prevent them from causing damage. They are classified based on their structure and mode of action. Acaricides are pesticides that are targeted to control mites they may have little or no activity against insects.

Many insecticides act at specific sites in the insect's nervous system . These usually provide very quick knockdown of insects that may ultimately die from dehydration or starvation. The insecticides usually are sprayed on infested plants or surface on which they rest. Depending on the pest, the insecticide may kill by direct contact with the spray droplets, ingestion of treated foliage, or prolonged contact with the residue on a treated surface.

Some Types of Insecticides

Cholinesterase inhibitors interfere with nerve impulse transmission at the synapse gap . Organophosphate (malathion, diazinon, acephate) and carbamate (carbaryl) insecticides belong to this group. They can be used as contact or residual insecticides. Once widely used for insect control, these insecticides have largely been replaced with other groups.

Bacterial toxins are produced by certain soil microorganisms. Examples include Bacillus thuringiensis (Bts) and spinosyns. Bt toxins disrupt the digestive tract of caterpillars so they are specific insecticides that must be eaten.

Botanical insecticides are defensive chemicals extracted from plants and used for pest control. Pyrethrins are extracted from the flowers of certain Chrysanthemum species. Pyrethroid insecticides are synthetic chemicals based on the molecular structure of the natural insecticide. Nicotine found in some solanaceous plants is the basis for neonictinoid family or insecticides. Both groups work on the nervous system. Azadirachtin is a chemical from the neem tree that has insect and disease control activity.

Insect growth regulators (IGRs) are chemicals based on hormones that regulate arthropod development. They disrupt metamorphosis so they are active against immature stages but not adults.

How Insecticides Enter the Target

Ways insecticides can enter pests (www.dropdata.org)

  1. Direct contact - the target insects are hit directly with spray droplets.
  2. Secondary or indirect contact by crawling over or resting on treated surfaces. The insecticide is absorbed through thin portions of the exoskeleton . These are especially effective against soft-bodied insects such as aphids, some caterpillars, thrips, etc. They are less effective against insects with thick or hard exoskeletons or hard wing covers (beetles), or hairy caterpillars. Insecticides on treated surfaces may enter insects through thin portions of the exoskeleton, especially the flexible areas of the feet.
  3. Ingestion of spray residues of contact insecticides on plants by pests with chewing mouthparts (beetles, caterpillars) or of systemic insecticides in sap by aphids, leafhoppers, plant bugs, etc.
  4. Repellents prevent insects from staying on or eating treated surfaces. Chemicals called anti-feedants stop insects from eating treated tissue.
  5. Fumigants are pesticides that become gases when released into the air or soil. Fumigants can be used to control nematodes and pathogens in the soil or insects in wood or stored products.
  6. Pheromones , chemicals used by insects for communication, can be used in insect control. For example, some female insects release sex pheromones to attract males for mating. Synthetic sex pheromones of some species can be released from dispensers in sufficient amounts to confuse males so they cannot locate females.

Broad spectrum insecticides kill a variety of arthropods, including beneficial and harmful species.

Narrow spectrum or selective products work on a limited, often related group of species. For example, "Bt" insecticides must be eaten in order to kill caterpillars. They are specific stomach poisons.

Factors That Affect Insecticide Performance

Successful control of an insect pest requires proper application, including coverage and timing of the treatment. Some products are effective against specific pests, such as caterpillars.Higher labeled rates are required for specific pests (such as fall armyworms) or pests that are in the later stages of their development (small grasshopper nymphs vs the larger adults).


Do Insecticides Stunt Plant Growth?

In this experiment, we will find out whether insecticides stunt plant growth or make no difference.

Research Questions:

Are insecticides harmful to humans?

Plants grow through a process called photosynthesis. This requires sunlight to take place. The chlorophyll located in the chloroplast of the plant cells grabs sunlight and starts the reactions that are needed to make the plant grow. Water is also needed in the growth equation because, like humans and animals, plants need moisture to quench their thirst.

Insecticides repel bugs. Bugs are not a good thing for plants (except for pollinating insects) as some of these insects create holes and contaminate the plants.

Materials:

  • Any insecticide (don't need a huge bottle)
  • Bean seeds
  • Soil on the ground
  • Water
  • Sunlight

Experimental Procedure:

  1. Plant 2 groups of seeds at a distance from each other in an outside yard. Make sure they will get the same amount of sunlight.
  2. Spray some insecticide on one group of seeds. Be sure to remember which one gets the insecticide.
  3. Observe the germination rate and growth of both of the seed groups.
  4. Every few days, spray the designated plant with insecticide.
  5. Record any difference you see in overall plant health and growth for several weeks, up to one month.

Suggested Chart

No Insecticide

Terms/Concepts: Insecticide Plant Growth Photosynthesis

Greene, Stanley A. Pohanish, Richard P. (editors) (2005). Sittig's Handbook of Pesticides and Agricultural Chemicals. SciTech Publishing, Inc. ISBN 0-8155-1516-2.

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Pest Control from the Middle Ages to the Victorian Era

In the span from the Middle Ages to the Victorian era, science moved from the realm of religion and magic to practical study. The disciplines of chemistry and biology were embraced, opening up studies into chemical compounds, reactions, and chemical synthesis. Pest control methods definitely benefited from this pursuit of knowledge. Older methods of pest control were still in use (removal, barriers, botanicals, and elemental salts) but the mechanisms behind their efficacy were still being discovered.

The 19th century marked the dawn of manufactured chemical pesticides, when chemicals began to be extracted from their botanical sources and were purified in laboratories. It was at this time that nicotine compounds were purified from tobacco, pyrethrums were extracted from flowers, and rotenone isolated from roots. In addition, cyanides were recognized as toxic compounds in the pits of some fruits.

During this era, chemical compounds were blended and produced for the purpose of pest control. In 1814, an inorganic compound of copper (II) acetoarsenite called “Paris Green” was introduced as a pigment. By 1867, Paris Green was widely sold as an insecticide and rodenticide. In fact, Paris Green paints even continued to be produced up until the 1960s.

Similarly, the Bordeaux Mixture was developed in the late 19th century to fight the Great French Wine Blight. Its mixture of copper (II) sulfate and calcium hydroxide was designed to combat fungal and mildew infections in vineyards.

It was during the Victorian era that traditional methods of pest control were formally investigated and put to the scientific method. As a result, all of the chemical compounds that were historically available in their botanical forms (e.g., rotenone in roots and pyrethrums in chrysanthemums) were purified for commercial and home use, and elemental compounds were blended to create more efficient pesticides. The humble beginnings of simple, natural repellents and physical pest controls grew into chemical and agricultural industries seeking out new and improved methods.


Sun and Soil, Water and Worms, Plants and Pesticides…and HEMP

I am no expert. I have never been a farmer. I don’t even garden much. So why would I know anything about the Earth/Plant life cycle? It has to do with worms. I actually worked as a salesman for a worm co-op at one point. I would arrange lectures about worms, the potential of worm castings (manure from worms) and the market demand for organic fertilizers. During my events, I would often have guest biologists from local universities come and give a sort of ‘Soils 101’ for guests. So here it is, for what it’s worth, the best a lay-person such as myself can recall.

Dirt is dead. It is crushed minerals broken down through the forces of nature. Soil is alive! It is a rich panoply of micro-organism and vegetable matter in various stages of decay. Good farmland is made up mostly of soil. As vegetable matter decays it is broken down by animals, insects, nematodes and micro-organisms. The by-product of this process are the deposits of nutrients that plant roots need. Thus the cycle of life. Plants grow, they are eaten or broken down by nature, which results in decay which feeds smaller living organisms, which produce the nutrients needed by plants to grow.

The sun is the primary energy source which drives this process. Water is the conveyance of this cycle. You can think of the sun like sipping through a straw. When the sun hits the plants, it “sips” the water which causes it to come up through the roots and stem. The genetics of the plant, combined with sunlight and water cause leaf and fruit and oils and seeds and everything else the plant produces. The plant puts off oxygen and more and then animals and insects can feed.

Worms are the multiplier of this effect. Worms do ingest particles of soil, but they aren’t really “eating” the soil. The process that takes place in a worm is that it feeds on the fungi and microbes attached to that particle of soil and they incubate life for the micro-organisms that benefit from this process. What comes out of a worm is that same particle of soil now coated a rich biology of life-giving nutrients for plant roots. They turn the soil, aerate the soil and cause the soil to retain water closer to the surface where plant roots can reach it

Pesticides, Chemical Fertilizers and Growth Agents

In our industrialized age, we have invented an abundance of chemistry to “help” with plant production. We can grow crops faster, larger, deeper in color and more resistant to weeds, disease and pests. Unfortunately, many of the chemicals we use today actually kill the soil, kill the worms, and turn our soil into Dirt. Each year, more of the chemicals are now needed to continue plant production. The larger, more colorful vegetables and fruits are now only hollow shells with greatly reduced nutrient content compared to the produce of generations past. We need to eat much more of the fruits and vegetables to get even a portion of the nutrients that used to be available in the slower, uglier produce grown naturally. The farmland is burning out (partly because there are no longer any worms in it), and farmers are now dependent on chemical fertilizers – much like an addict becomes dependent on what makes him sick – lest the farmers go bankrupt for having no crops.

Hemp is not the cure-all for this vicious cycle we have got ourselves into, but it can help. Hemp outpaces weeds, is naturally pest resistant and grows at amazing rates without chemical enhancement. Best of all, it produces one of the most human-friendly crops on Earth. Hemp seeds, oils and leaves are amazingly great for human consumption and entire civilizations have had hemp as a staple since mankind has walked the Earth. Additionally, hemp crops provide a restorative component to damaged soils. It can be used as an alternative crop in rotation for wheat and for cotton to “rest” the soil. Hemp is even being grown around Chernobyl to help restore irradiated soil.


Conclusion

In this review, we described the different ways in which pesticides may disrupt the hormonal function of the female reproductive system and in particular the ovarian cycle. Pesticides are not one common substance, but comprise a large number of distinct substances with dissimilar structures and diverse toxicity which may act through different mechanisms. Therefore, it is most likely that not just one but several of the above-mentioned mechanisms are involved in the pathophysiological pathways explaining the role of pesticide exposure in ovarian cycle disturbances ultimately leading to fertility problems and other reproduction toxic effects. A disadvantage of the studies described is that they were mostly laboratory animal and cell culture studies. These often provide the first indications of potential reproductive effects of a chemical, but it is difficult to extrapolate the effects found in laboratory animals to effects that might be expected in women. Therefore, we also reviewed epidemiological studies which lead to the conclusion that exposure to pesticides may be associated with menstrual cycle disturbances, reduced fertility, prolonged time-to-pregnancy, spontaneous abortion, stillbirths, and developmental defects. However, in most of these studies specific information on pesticide exposure and the pathophysiological mechanisms involved was missing. Furthermore, we have to take into account that dose, timing, and duration of exposure are critical to the ability of a pesticide to cause harmful effects. Nevertheless, real-life occupational exposures to pesticides appear to have adverse effects on female reproduction. In future research, information on the ways in which pesticides may disrupt the hormonal function as described in this review, can be used to generate specific hypotheses for studies on the effects of pesticides on the ovarian cycle, both in toxicological and epidemiological settings.


Pesticides could hike risk of catching a parasitic worm

Pesticides are a double-edged sword: They make farming more productive, but they can harm wildlife and people if not used properly. Now, ecologists have identified a new threat from pesticides in the developing world. By killing off insect predators of worm-infested snails, they can raise the risk of schistosomiasis, the second most common parasitic disease after malaria.

“It’s a ground-breaking article,” says Russell Stothard, a parasitologist at the Liverpool School of Tropical Medicine in the United Kingdom, who was not involved in the research.

Schistosomiasis is a debilitating disease caused by a parasitic flatworm. Some 258 million people are infected, mostly in Africa. The worm spends part of its life in freshwater snails, which release larvae that can penetrate the skin of someone swimming, bathing, or washing clothes. The centimeter-long worms spread through blood vessels, causing fever, diarrhea, anemia, and stunted growth. Immune responses can damage the kidneys and other organs. When infected people relieve themselves, the worms’ eggs can spread into streams or ponds via their urine and feces. There, they hatch and seek out new snails, beginning their life cycle again. Schistosomiasis can easily be treated with drugs, but where the parasites are endemic, people quickly become reinfected.

The leader of the new research, ecologist Jason Rohr of the University of South Florida in Tampa, had previously studied a similar parasitic flatworm in amphibians. His research showed that common agricultural chemicals, like fertilizer, can worsen the situation for frogs. When these chemicals enter streams and ponds, they increase the amount of algae, which is then eaten by snails that serve as a host for the flatworms. That boosts their population and leads to more parasite infections in frogs.

The similar life cycles of the amphibian flatworm and the one that causes schistosomiasis made Rohr and his colleagues wonder whether agricultural pollution might also affect disease transmission. They created a simple ecological model inside 60 open tanks. After filling each with 800 liters of pond water, they added two species of snails that spread the schistosomiasis parasite, algae for the snails to eat, and two kinds of predators—crayfish and water bugs. Finally, they spiked the tanks with three kinds of farm chemicals—fertilizer, herbicide, and insecticide—in various combinations. The concentrations were typical of streams and ponds near corn fields in the United States.

As expected, fertilizer increased the amount of algae in the tanks, which in turn swelled the number of snails. The herbicide also led to more food for the snails, because it predominately killed microscopic algae that clouded the water. When these died, the water cleared, allowing more light to reach larger algae growing on the bottom of the pond—the snails’ food. An epidemiological model of schistosomiasis suggested that the increase in snail population from this typical amount of fertilizer would jack up the risk of transmission to humans by 28%.

The insecticide, chlorpyrifos, had an even bigger effect by killing the two predators of the snails. Water bugs stick their heads inside the shell, bite the mollusc, inject digestive enzymes, then slurp up the remains. The 20-centimeter-long crayfish rely on brute force, crushing the 2-centimeter-long snails. “They’re absolutely voracious,” Rohr says. With these predators gone, the snail population exploded. In such a scenario, disease risk to humans would rise 10-fold, the team reports in a preprint posted this week to bioRxiv. Although only one concentration of insecticide was added to the tanks, the model indicated that lower concentrations in ponds would still have substantial impacts on parasite transmission.

The findings identify what looks like a “strong risk factor” for schistosomiasis, says Joanne Webster, a parasitologist at Imperial College London who was not involved.

Dams have also caused an increase in schistosomiasis in many countries, because snails live in the reservoirs and irrigation channels. In some places, dams have also caused a decline in the natural predators of snails, such as fish, crayfish, and prawns. The combination of new habitat from irrigation and runoff of pesticides may be a “perfect storm” for schistosomiasis where agriculture is intensifying in the developing world, Rohr says.

Rohr is now investigating the impact of insecticides on snail predators and disease transmission in northwest Senegal, as part of an experiment run by a research partnership called the Upstream Alliance, based in Pacific Grove, California. This project has reintroduced prawns near several villages to evaluate their efficacy in controlling freshwater snails. Rohr will study whether helping farmers switch to insecticides less toxic to prawns could lessen the burden of schistosomiasis, while maintaining food production. “In schistosomiasis-endemic regions, we need to think more carefully about the impact of agrochemicals,” he says.

The study highlights the complex links between agriculture and disease, says Charles Godfray, a biologist at the University of Oxford in the United Kingdom. By boosting agricultural productivity, pesticides and other chemicals can help raise people out of poverty and lessen malnutrition, which worsens diseases. “The really clear thing is the importance of precision agriculture, in which agrochemicals are used as efficiently as possible, with as little runoff as possible.”


References

● Brinkhurst, R. O. and S. R. Gelder (1991) Annelida: Oligochaeta and Branchiobdellida, In Ecology and Classification of North American Freshwater Invertebrates (T. H. Thorp and A. P. Covich, Eds.), Academic Press, New York.

● Drewes, C. D. (1999) Helical swimming and body reversal behaviors in Lumbriculus variegatus (Family Lumbriculidae). Hydrobiologia 406:263-269.

● Drewes, C. D. and R. O. Brinkhurst (1990) Giant fibers and rapid escape reflexes in newly hatched aquatic oligochaetes, Lumbriculus variegatus (Family Lumbriculida). Invertebrate Reproduction and Development 17:91-95.

● Drewes, C. D. (1997) Sublethal effects of environmental toxicants on oligochaete escape reflexes. American Zoologist. 37:346-353.

● Drewes, C. and K. Cain (1999) As the worm turns: Locomotion in a freshwater oligochaete worm. American Biology Teacher 61:438-442.

● Drewes, C. D. and C. R. Fourtner (1989) Hindsight and rapid escape in a freshwater oligochaete. Biological Bulletin (Woods Hole) 177:363-371.

Drewes, C. D. and C. R. Fourtner (1990) Morphallaxis in an aquatic oligochaete, Lumbriculus variegatus: Reorganization of escape reflexes in regenerating body fragment. Developmental Biology 138:94-103.

● Jamieson, B. G. M. (1981) The Ultrastructure of the Oligochaeta, Academic Press, New York.

● Lesiuk and Drewes (1999a) Autotomy reflex in a freshwater oligochaete, Lumbriculus variegatus. Hydrobiologia 406:253-261.

● Lesiuk, N. M. and C. D. Drewes (1999b) Blackworms, blood vessel pulsations, and drug effects. American Biology Teacher 61:48-53.

● Lesiuk, N. and C. D. Drewes (2001a) Behavioral plasticity and central regeneration of locomotor reflexes in the freshwater oligochaete, Lumbriculus variegatus. I. Transection studies, Invertebrate Biology 120:248-258.

● Lesiuk, N. and C. D. Drewes (2001b) Behavioral plasticity and central regeneration of locomotor reflexes in the freshwater oligochaete, Lumbriculus variegatus. II. Ablation studies. Invertebrate Biology 120:259-268.

● Stephenson, J. (1930) The Oligochaeta, Clarendon Press, Oxford.


Watch the video: How do worms affect plant growth? (August 2022).