Tuesday, April 16, 2019

LIMITATIONS OF ATTRACTANTS

Development of workable pheromone mixtures, traps and application methods is time consuming and costly. It requires -
Knowledge of physiology of pest for design of traps - size, shape, material, trap opening, the density of traps required and their positional placement in the crop.
Development of a substrate which will release the pheromone in a controlled, consistent rate.
Knowledge of the active ingredients in a pheromone - the optimal concentration of each component and whether this changes over time.
Financial investment - These chemicals also need to be registered, requiring lots of data. Since these cannot be patented, there is little money to be made from their commercial development and so it is usually left to government agencies.
7. Legal control (Quarantine)
In 1971 a viral disease called Venezuelan encephalitis of horse spread by a vector was wide spread in Central America and was introduced into North America. By restricting the movement of horses and embarking on mass immunization the disease was curtailed.
8. Integrated Pest Management (IPM)

REPRODUCTION IN INSECTS
Insects are known to reproduce in a variety of ways. This has helped in the propagation of species and survival in adverse conditions. The following are different ways by which insects reproduce
1. Parthenogenesis:- Some insects are able to reproduce without fertilization of eggs and this type of reproduction is called parthenogenesis. Insects that reproduce this way multiply rapidly e.g. aphids.
2. Paedogenesis:      The immature stages of insects develop functional sex organs and reproduce. This is called reproduction by immature stages, e.g. the larvae stage. Examples of insects that reproduce this way include Micromalthus debilis of the family Ceccidomyiidae.
3. Polyembryony:-Some insects are able to bring up 2 or more embryo from a single egg and these embryos can subsequently develop into individuals. This is common among the parasitic wasps of the family Encyrtidae, Braconidae.
4. Hermaphroditism:- A single insect has both the male and the female reproductive organs. In this case both the production of eggs and the egg fertilization is carried out by the same individual e.g. Icerya purchasi (Stain insect of cotton).
5. Viviparity:-         This refers to reproduction of living young by insects without a prior lying of eggs. In some insects they are able to produce single egg and single embryo at the same time nourished within a special follicle within the female so that a mature larva is deposited e.g. Glossina spp
6. Oviparity:-      This is the most common type of reproduction. The eggs are laid by the female on a suitable site or substrate e.g. in/on the soil, on plant tissues or any other place where development can take place. The eggs are usually left to hatch but in most cases the eggs are tender enough for the insects to show maternal care.

MODULE 3
Unit 1. Formulation of insecticides
Unit 2. Different equipment for the application of insecticides
Unit 3. Calculations to determine the rate of insecticide application

UNIT 1: FORMULATION OF INSECTICIDES
The biological activity of a pesticide, be it chemical or biological in nature, is determined by its active ingredient (AI - also called the active substance). Pesticide products very rarely consist of pure technical material. The AI is usually formulated with other materials and this is the product that is sold, but it may be further diluted in use. Formulation improves the properties of a chemical for handling, storage, application and may substantially influence effectiveness and safety. Formulation terminology follows a 2-letter convention: (e.g. GR: granules)
Water-miscible formulations

Pesticides are available in various "formulations". A formulation is simply the form of a specific product that you use. A pesticide formulation is a mixture of chemicals which effectively controls a pest. Formulating a pesticide involves processing it to improve its storage, handling, safety, application, or effectiveness. A pesticide formulation typically consists of an active ingredient, plus several inactive materials called adjuvants, or additives. The main purpose of additives is to increase the effectiveness of the active ingredient. Some common additives include spreaders, stickers, wetting agents, compatibility agents, and foaming agents.
By far the most frequently used products are formulations for mixing with water then applying as sprays. Water miscible, older formulations include:
EC Emulsifiable concentrate
WP Wettable powder
SL Soluble (liquid) concentrate
SP Soluble powder

DIFFERENT TYPES OF FORMULATIONS
The following are some of the most common kinds of pesticide formulations available, along with a description to give you a better understanding of what they are:
1. Dusts (D) are made up of a finely ground mixture of active ingredient combined with clay, talc, or other powdered materials. Dusts are intended for dry use and should never be mixed with water. The percentage of active ingredient in a dust is generally quite low. Dusts are commonly used for interior wall void and perimeter treatments, as well as for crop-dusting.
2. Granules (GR) are hard, dry particles made up of porous materials and active ingredient. The percentage of active ingredient in a granule formulation is higher than that of a dust but lower than that of an EC. Granules are usually more safe to apply than dusts or ECs. Granular formulations are used most often for soil treatments. Granules will not cling to plant foliage, so that they may be directly applied over plants or soil.
3. Aerosols are sold in cans and contain one or more active ingredients under pressure. Aerosols pesticides are sold most often for home and garden use, not for agricultural use. The percentage of active ingredient in aerosols is usually very low. One of the main advantages of aerosols is that they are convenient and easy to use. Many aerosols are used for killing pests on contact, or for time-released control of flying pests.
4. Wettable powders (WP) A wettable powder is an insecticide or other pesticide formulation consisting of the active ingredient in a finely ground state combined with wetting agents and sometimes bulking agents. Wettable powders are designed to be applied as a dilute suspension through liquid spraying equipment. Wettable powders are dry and powdery. They appear similar to a dust but contain additional wetting and dispersing agents so that water may be added for maximum effectiveness. Wettable powders are also more highly concentrated than dusts to contain more active ingredient. Wettable powder formulations do not form a true solution when water is added, so frequent agitation of the spray tank is required to keep the formulation in suspension.
5. Emulsifiable concentrates (EC) are liquid formulations where the active ingredient is dissolved in oil and an emulsifier (a blend of active ingredient, organic solvent, and surfactants) is added so that the formulation may be mixed with water or oil for spraying. When the solution is diluted into water, a spontaneous milky emulsion forms with dispersed phase droplets in the size range of 1 to 25 μm. ECs are among the most widely used formulations, along with wettable powders. ECs typically contain two to six pounds of active ingredient per gallon. Unlike wettable powders, ECs require very little agitation and are easy to handle.
6. Flowable liquids (F or L) are made with active ingredients that cannot be dissolved completely in water or oil, so the active ingredient is ground up and suspended in a liquid with other suspending agents. The formulation is then ready to mix with water for application. Flowables are easy to handle, will not clog spray nozzles, and require only moderate agitation.
7. Solutions and water soluble concentrates (S) are liquids in their original state and are fully soluble in water and any other solvent. Solutions that are prepared the right way will not leave unsightly residues or clog spray nozzles.
8. Encapsulated pesticides are a new kind of formulation in which the active ingredient is held in a very small capsule. These capsules are then suspended in a liquid. This formulation of suspended capsules is then mixed with water and maybe applied with a sprayer. Encapsulated pesticides are safe and easy to use, but may pose a threat to bees when they carry the capsules back to their hive.
9. Soluble powders (SP), are dry formulations similar to wettable powders, but the difference is that when added to water a soluble powder will dissolve completely and form a genuine solution (whereas a wettable powder does not). Some agitation may be required to dissolve the soluble powder initially, but once a solution, agitation is not needed. The percentage of active ingredient in a soluble powder is high compared to ECs and WPs, and there are not currently many SP formulations available.
10. Dry flowables are very similar to granules in appearance, but behave in the same way as wettable powders. Dry flowables have several advantages over WPs because of their shape: they can be easily "poured" and measured just like liquid, and are safer to use because very little dust is released into the air when they are mixed and measured. Dry flowables contain very high percentages of active ingredient.
11. Poisonous baits are food-like substances mixed with a pesticide specifically designed to attract and be eaten by insects or other pests and eventually poison them to death. Baits are commonly used for rodent control, including mice and rats. However, baits are also used to control roaches, ants, flies, and other insects. Bait formulations can be used indoors or outdoors. When compared to ECs or other formulations, the percentage of active ingredient in a bait is low.
12. Ultra-Low Volume (ULV) are liquid formulations with uniform droplet sizes. The droplets are usually very small and no water is used. They come in formulations that are ready to use (RTU). Because no water is added, lower quantities are used per unit area.
Newer, non-powdery formulations with reduced or no use of hazardous solvents and improved stability include:
SC Suspension concentrate
CS Capsule suspensions
WG Water dispersible granules

How to choose a Formulation
Any given active ingredient can often be purchased in more than one formulation. For example, the active ingredient Deltamethrin is available as a granule (DeltaGard G Granules), a suspension concentrate (Suspend SC), a dust (Delta Dust), and an aerosol (D-Force HPX). Same active ingredient, four different products. The reason for this is that different formulations of the same active ingredient behave differently. Therefore, a deltamethrin dust is perfect for application into wall voids where it coats the inner wall and controls crawling pests, while a deltamethrin aerosol is more suited towards contact control of flying pests.
Knowing the characteristics of a given formulation will help you to choose the right product for your needs and use that product more effectively. Here are some points to consider when choosing a formulation. This information can usually be found on the product label:
Percent of active ingredient
Ease in handling and mixing
Personal safety risk
Type of environment (agriculture, forest, urban, etc.).
Effectiveness against the pest
Habits of the target pest
The crop to be protected
Type of application equipment or machinery
Danger of drift or runoff
Possible injury to crop
Cost

Combining Different Formulations
Sometimes two different pesticide formulations are combined to create a more effective application. However, not all pesticides can be combined safely. Before combining various formulations, always consult the label or a pest control professional to find out whether the two formulations are compatible. The mixing of two incompatible pesticide formulations may be fatal. Incompatibility can be either chemical or physical.
These incompatibilities should be clearly indicated on the product label, however, it is still a good idea to contact a professional if you have any questions.

ADVANTAGES FO INSECTICIDES
It is employed as a result of convenience, simplicity, effectiveness as well as flexibility
They are used when other control methods fail or an emergency situation arise e.g. locust invasion.
Insecticides have rapid curative action in preventing economic damage. Lethal action is rapid and a high population of pest population is usually accomplished or obtained within a few hours to a day or 2 days, e.g. swamps of migratory locust (Locusta migratoria) have been successfully controlled by aircraft spraying of insecticide.

FACTORS TO BE CONSIDERED IN USE OF INSECTICIDES
Proper pest identification. The damaging insect must be properly identified to ensure that the right insecticide is used for its control.
Efficiency of the pesticide: depending on the insect to be controlled, a systemic or contact insecticide will be selected for use.
Pesticide compatibility: the compatibility status of the insecticide should be known prior to usage to ensure that there is no adverse effect, or change in insecticidal properties or change in phyto-toxicity when they are mixed.
Degree of phytotoxicity: Insecticides applied adversely affects the host crop been protected. Most insecticides are phyto toxic but usually at higher doses than required for pest control. The susceptibility of plants to chemical injury also varies from one plant to another and a term used for this is insecticide selectivity. An insecticide maybe toxic to the seedling stage and not phyto-toxic to the mature stage or it may be phyto-toxic to maize or cowpea and not phyto-toxic to okra.
Insect resistance to pesticides: This is an increasing problem in that a pesticide dose that normally controls certain insects over time can no longer control the same insects because of constant spraying which makes the insects grow resistant strains and this is countered by increasing the dose administered or changing the insecticides to one that has a different mode of action.
Synergism: refers to the interaction of chemicals. Some chemicals have the property of increasing the toxicity of another chemical so that the total effect produced when such chemicals are applied is greater than when either one is applied singly e.g. if 2 chemicals A & B
Chemical A kills-16 pests
     B kills-14 pests
A + B will kill ----30 pests---additive
But if A & B are mixed and about 50% are killed, this is positive synergism but if the number of the pests reduces then it is negative synergism.
Pesticide persistence: Pesticides that are highly persistent in human, livestock and the environment though effective are dangerous, e.g. DDT has been banned globally due to its high level of persistence in the environment leading to contamination of soil and ground water. Insecticides with low persistence (pyrethrum) are more favoured to prevent environmental contamination.
Frequency of application: insecticide application must be timed accurately in order to prevent bad results. The timing should be done to concise with the stage of development at which the pest is most susceptible. Also the safe interval should be considered which is the last time of application before harvesting; so that we don’t have un-decomposed residual chemicals in the produce.
Unit 2. Different equipment for the application of insecticides
Equipment typically used for pesticide application may be divided into six general categories:
1. Ground sprayers
2. Applicators for solid formulations
3. Aerial sprayers
4. Fumigation equipment
5. Foggers
6. Chemigation
The following is an overview of the more common types of pesticide application equipment and some of the areas in which they are typically used.
Ground Sprayers for Liquids
Air blast Sprayers
Air blast sprayers are most often used on orchard crops, grapes and some berry crops. Air blast sprayers have nozzles placed in a very high speed air stream produced by a fan. The air stream propels the very fine spray droplets to the target. In addition, the air stream creates leaf movement, allowing better coverage of insecticides and fungicides.
Boom Sprayers
Boom sprayers have multiple nozzles spaced over the length of the boom. Tractor mounted booms sprayers are generally used to broadcast liquid pesticides over large areas such as agricultural crops or golf course turf. Field sprayers may have tank sizes ranging from 500 to 4000 litres and boom widths ranging from 6 to 36 metres.
Hand-held Sprayers
Hand wand sprayers are light weight and hand operated. Their name is derived from the long metal extension that ends in an adjustable nozzle. A hose attaches the "wand" to a small portable tank or larger, stationary one. These sprayers can vary widely in type and pressure capability. The most commonly seen handwands are compressed-air sprayers. They may be used in a variety of settings such as spot herbicide application on turf or along roadsides, indoor crack and crevice treatments or greenhouses.
Backpack Sprayer
A backpack sprayer has a spray tank that fits comfortably on the back like a knapsack. The applicator pumps the sprayer handle to build up pressure in the tank and applies the product through a small hose / single nozzle assembly. Some backpack sprayers are battery or gas powered. The usual tank capacity is about 15 litres so that the tank weight is not excessive to the handler. Backpack sprayers are commonly used to treat small areas and may be used for spot herbicide application such as on turf or along roadsides and in greenhouses.
Applicators for Solid Formulations
Granular Spreader
Granular spreaders are available to broadcast pesticide granules over an entire field surface or in bands that correspond to crop rows. Application equipment may use gravity or a positive metering mechanism to regulate the flow of granules. Small, hand-operated granule dispersal equipment (e.g., push rotary spreaders) may be used to treat smaller areas such as in landscaping.
Dust Applicators
Equipment used to apply products as a dust range from simple shaking devices to power dusters. Dusts may be applied to indoor residential (crack and crevice) and outdoor residential (ornamental) settings or, in some cases, in greenhouse or agricultural settings.
Aerial Sprayers
Fixed wing aircraft and helicopters may be used for applying pesticides either as a solid or liquid (including ultra-low volume spray). Fixed wing aircraft may be preferred when there are large, continuous areas that may be sprayed with a minimum number of turns. Helicopters are useful for treating discrete or isolated patches.
Fumigation
A fumigant is a pest control product that, at a specific temperature and pressure, can exist in the gaseous state in sufficient quantities to be lethal to a pest organism. Fumigants may move through air spaces between soil particles (soil fumigation) or through air in structures (space fumigation). Space fumigation generally requires the gas be contained within the treatment area for a specified period. Following treatment, aeration takes place under controlled conditions until fumigant levels have dropped below specified levels.
When soil is fumigated, liquid fumigants may be applied using equipment similar to small field sprayers; however, spray nozzles are replaced with hose shanks that inject the liquid fumigant into the soil where it will volatilize.
Fogging Equipment
Outdoor foggers or space sprayers can be mounted on a truck or aircraft and used to form a cloud of small droplets that are suspended in air. This application method is often used to control adult mosquitoes and black flies. Two types of ground equipment are used for space sprays.
Thermal foggers use heat to vaporize the insecticide into a highly visible dense fog. Diesel is often used as a carrier. Although used in the past, thermal fogging has been largely replaced by non-thermal fogging in Canada and the United States.
Ultra-low volume (ULV) sprayers, also known as "cold foggers", use concentrated insecticides with no carrier. Cold fogging produces small droplets of insecticide using special nozzles to break up the liquid droplets. As the droplets are microscopic in size, the spray area is increased, making it possible to effectively use very low application rates of the insecticide.
Fogging equipment may also be used indoors, such as in greenhouses, warehouses and farm buildings. A range of stationary/automatic or hand-held equipment is available for low volume applications.
Mist blowers produce very fine droplets by air blast generation. As air is the major carrier, the concentration of the pesticide in the spray mixture may be high.
Thermal foggers use heat to break up the pesticide into fine droplets. These products are usually formulated at low concentrations in an oil-based carrier.
Ultra-low volume or ultra-low dosage (ULV/ULD) equipment reduces the volume by reducing the use of water or any other liquid carrier. Pesticides must be specially formulated for this application.
Electrostatic equipment uses air to atomize or form spray droplets; the charged droplets are attracted to plants.
Chemigation
Chemigation is the application of chemicals, such as pesticides and fertilizers, to crops through an irrigation system (e.g., sprinkler, flood, furrow, drip or trickle) by mixing them with the irrigation water.
What Can Be Done to Reduce Exposure During and After Pesticide Applications?
Any unnecessary exposure to pesticides should be reduced or eliminated. Pesticide applicators can minimize exposure to themselves and others by carefully following all application instructions and precautionary statements on the product label.
It is good practice to minimize the presence of bystanders in the area while pesticides are being applied and immediately after. When a worker re-entry interval (the time after application at which re-entry to the treated area does not raise concerns regarding risk) is specified on the product label, it must be respected. Re-entry intervals are not specified for products applied in residential areas as it is not considered feasible to restrict entry into these spaces. As such, these products are only registered if they do not pose unacceptable risks to those working or playing in the treated area immediately after application. However, to minimize any unnecessary exposure to pesticides, it is still good practice to wait until the product has dried before re-entering the treated area to work or play.

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