Chemical control Flashcards
What would be the consequences of a global ban on the use of all pesticides in food crops?
Pesticides are necessary to control many plant diseases
Production of many crops would not be possible without them
Describe the series of disasters in the European wine industry that led to the discovery of the Bordeaux mixture.
powdery mildew was introduced from north America in 1845 probably on wild grape plants brought to France. French wine production dropped by 80%. it was eventually controlled by extensive application of sulfur.
More grape germplasm was imported from North America to develop resistant grape cultivars. This led to the introduction of root aphid insect Phylloxera. French vineyards were replanted with Phylloxera-resistant rootstocks from North America
During this importing of resistant grape rootstocks the downy mildew pathogen Plasmopora viticola was introduced. Sulfur did not control downy mildew.
The modern fungicide era began as a result of this series of disasters. Alexis Millardet noticed that grapes treated with a mixture of lime and copper sulfate (to discourage pilfering) were healthy. THrough experiments he learned that copper ions were toxic to the fungus. THis mixture became the Bordeaux mixture that is still used today
Which regions of the world use the majority of fungicides and other pesticides?
Western Europe, Europe in general
Which crops receive the most fungicides world-wide? Which crops receive the most fungicides in Europe?
World-wide: Tree and vine crops
Europe: cereals
Describe the general properties of inorganic and organic fungicides.
Inorganic: compound does not contain carbon atoms, target many metabolic pathways in pathogen, disrupt many different proteins and cellular functions
organic: contain carbon, mainly oxygen, hydrogen, nitrogen and sulfur, their mode of action sometimes is not known or well understood, low toxicity to humans and plants, degraded by sunlight and microbes (no accumulation), more environmentally friendly
Describe the general properties of protectant and eradicant fungicides.
Protectants can protect platn tissue from infection
Eradicants can kill superficial pathogens, may have curative action if they can eliminate the pathogen completely from the infected plant
Describe the general properties of systemic and contact fungicides.
Contact fungicides are only locally active, have to be applied many times to protect new plant tissue, wash off with rain
Systemic fungicides can be absorbed and systemically be translocated throughout the plant, can be applied fewer times
Describe the properties of an ideal fungicide.
low lethal dosage for targeted organisms, no injury to host, non-toxic to humans and animals or other non-targeted organisms, no undesirable flavours, odors or poisonous properties, compatible with other chemicals, it will adhere tenaciously to plant surfaces and resist weathering, easy to prepare and apply, low cost
What is a safener? A spreader? A sticker?
Safeners reduce phototoxicity and make compound safer
Spreader is a detergent that is added because it lowers the surface tension and will make fungicide spread better
Stickers are starches and oils added to make the fungicide stick better on the plant
What are the advantages of applying a fungicide to seeds? Would it be better to apply a contact fungicide or a systemic fungicide to a seed? Explain your answers.
to prevent seed decay or damping off
limited ecological and environmental damage
chemical is applied directly where needed
very few grams of active ingredient is applied per hectare compared to sprays and powders that are applied to leaves
seed treatments have diminished seedborne diseases, especially smuts and bunts
it would be better to apply a systemic fungicide, the systemic activity can persist in seedlings long enough to protect young plants from the first wave of inoculum
List three inorganic fungicides. Which inorganic fungicide class exhibits systemic activity?
Copper compounds
Sulfur compounds
Carbonate compunds
Systemic activity: Phosphate and phosphonate compounds
List three contact organic fungicides.
organic sulfur compounds, the dithiocarbamates
Heterocyclic compounds
Aromatic compunds
List three systemic organic fungicides.
Benzimidazoles
Acylalanines (Phenylamides)
Ergosteral biosynthesis inhibitors
What type of fungicide is most commonly used worldwide?
The most widely used fungicide in the world is the Bordeaux mixture
What diseases are controlled with antibiotics?
Fire blight in apple and pear orchards
