INTEGRATED PEST MANAGEMENT STRATEGIES

BY

DENNIS OWUSU BOATENG (TECHNICAL OFFICER)

BUNSO COCOA COLLEGE

CSSVD CONTROL UNIT (COCOBOD)

INTRODUCTION

•      Crops are vulnerable to attack by pests.

•      Pest damage can range from slight damage that has no effect on the value of the harvested product to severe damage that kills plants, significantly reduces yield of the crop, or reduces its market value. 

•      Crop pests include insects and mites, weeds, diseases, and nematodes.

•      Effective management of pests is based on thorough consideration of ecological and economic factors.

•      The pest, its biology, and the type of damage are some of the factors that determine which control strategies and methods, if any, should be used.  Pest management decisions largely determine the kind and amount of pesticides used.

• •           Pest management decision re-present a compromise between the value of the product    and the extent of the pest damage, the relative effectiveness and cost of the control measures and  the impact on the environment

IPM GOALS

•      The goal of IPM is to use all appropriate tools and tactics to keep pest populations below economically damaging levels and to avoid adverse effects to humans, wildlife, and the environment.

•      These tools include cultural, biological, and chemical control methods.

•      Management decisions are based on information gathered about the pest problem and crop.

•      Then you use a combination of control measures that best suits the problem.

IPM TOOL

•      FIELD SCOUTING /MONITORING

•      ECONOMIC THRESHOLDS

•      CONTROL STRATEGIES

FIELD SCOUTING /MONITORING

•      Field scouting is an important part of any IPM program because it helps define the pest problems.

•      Correct identification and location of each pest in a crop are necessary for a successful pest management program.

•      These can be accomplished by regularly scouting fields.

•      A scouting trip through a field reveals what pests are present, the growth stage of the pests and the crop, the location of the pest in the crop, whether the pests are parasitized or diseased, the pest population, if the population is increasing or decreasing, and crop condition.

•      A scouting program should include accurately written records of field locations, field conditions, previous pest infestations, and control measures.

•      Insect pests can be monitored in several ways.

•      The most common methods are directly counting the number of insects present and/or estimating the amount of insect damage.

•      Insect counts are usually expressed as the number of insects per plant or plant part (e.g., number of insects per leaf).

•      Insect crop damage is often expressed as percentage of the plant damaged (for example, percent leaf defoliation).

•      Other scouting methods include collecting insects with a sweep net shaking crop foliage and counting dislodged insects, and trapping insects.

ECONOMIC THRESHOLDS

•      An economic threshold is defined as the pest density at which action must be taken to prevent the pest population from increasing and causing economic damage.

•      Economic thresholds are constantly changing. They vary between fields, varieties, and crop growth stages.

•      Economic thresholds are a function of crop value and cost of control.

•      In general, a high-value crop will have a lower economic threshold; less pest damage will be accepted and control measures must be taken sooner.

•      If the control measures are expensive, the economic threshold is usually high.

•      High control costs mean it takes more crop loss to justify the control action.

•      Economic thresholds are often referred to as action thresholds.

•      When the pest population reaches the threshold, action is taken to reduce the population.

•      For insects, an economic or action threshold is typically expressed as the number of insects per plant or the amount of crop damage.

CONTROL STRATEGIES

•      CULTURAL CONTROL

•      BIOLOGICAL CONTROL

•   CHEMICAL CONTROL

CULTURAL CONTROL

•      Cultural control uses farming practices to reduce pest populations.

•      Implementing a practice such as tillage or crop rotation at the correct time can kill or reduce pest numbers or slow pest development.

•      Like all other control strategies, cultural control requires an understanding of the pest and the crop.

•      Cultural control measures are usually applied at the weakest stage of the pest’s life cycle.

•      Generally, cultural control methods are preventive actions rather than curative actions.

•      Cultural control methods work in three ways:

–     1. Prevent the pest from colonizing the crop or commodity.

–     2. Create adverse conditions that reduce survival of the pest.

–     3. Reduce the impact of pest injury.

PREVENTING COLONIZATION

1. Trap crop

Planting a small area with a   preferred host to attract the pest away from the crop. Once in the trap crop, the pest can be destroyed or controlled.

1. 2.            Physical barriers

Separating a pest and host with an object such as a wall to stop the pest from infesting. Example: in grain bins, it is extremely important to fill in all cracks and crevices with approved caulking material to prevent colonization by pests such as insects and rodents.

3. Crop rotation

A cycle in which different crops are planted in a field every year; the longer the rotation, the better the pest control. A crop rotation system helps control host-specific pests. A classic example of crop rotations is a corn-soybean rotation to control corn rootworms.

4. Delayed planting (timing)

Changing the planting date so that the host is not available when the pest is present. Eg. changing the planting date of wheat can control the Hessian fly. The adult fly is short lived and requires wheat at a specific vegetative state for egg laying. 

5. Cover crops

Utilizing plant competition by planting a secondary crop to prevent weeds from becoming established. Example: cereal grain cover crops provide a suitable environment for soybean seedling establishment while suppressing weeds.

CREATING ADVERSE PEST CONDITIONS IN THE CROP

•      Destroy crop residue, alternate hosts, and volunteer crops:

Eliminating the pest or pest habitat found in crop residue, or destroying alternate hosts of the pest found near or in the crop. Eg: planting wheat into corn residue increases the risk of wheat scab because the pathogen infects both hosts. Plant pathogens, mosaic virus, mite vector, fungi and bacteria, can survive in a field on volunteer crops and alternate hosts.

•      Tillage

Physically moving the soil around the crop. Tillage can destroy an insect, create physical and chemical changes in the soil that reduce pathogens, and destroy a weed’s roots and disrupt nutrient uptake.

•      Water management

Manipulating H₂0 to control a pest. Eg. fungal pathogens that infect pests such as the velvet bean caterpillar in soybeans are easily spread by overhead irrigation. H₂0 management can also be used to promote healthy crops, which can compete with weeds. Overwatering can increase the potential for plant diseases.

•      Spatial arrangement

            changing the spatial arrangement of the crop to reduce pest populations. Eg: when plant 
            spacing and row width are reduced, soybeans outcompete weeds. On the other hand, 
            close spacing may provide a favorable environment for disease to develop, eg. white  
             mold in soybeans and dry beans.

•      Allelopathy 

            One plant species eliminates a competing plant species through the release of toxic   
            chemical agents. It is weed management. Eg. in a conservation tillage system, leaving 
            rye residues can reduce the number of weeds.

REDUCE PEST INJURY TO CROP

•      Host-plant resistance 

The host plant’s ability to tolerate pest pressure. Plants have defense mechanisms that allow them either to affect the pest or withstand the pest’s damage.

•      Plant health

Maintaining strong, healthy plants that are better equipped to out-compete weeds, fight disease, and withstand insect damage

•      Harvest timing

Changing the time when a crop is harvested to reduce pest impact on yield. For example, cutting alfalfa early can reduce the effects of alfalfa weevil or leafhopper damage. Cutting too early, however, weakens the roots and can make the plant more susceptible to root diseases.

•      Storage practices

Handling, curing, and storage practices to prevent the spread of disease during storage. For example, low temperature and good ventilation are essential to minimize losses in potatoes.

BIOLOGICAL CONTROL

•      Parasitoids

Organisms that must live in or on another organism to develop. A parasitoid is usually an insect that develops and feeds inside another insect. An adult parasitoid lays an egg in or on a host insect. When the parasitoid egg hatches, the larva feeds on the host insect. Eventually, the developing parasitoid kills the host insect by eating it from the inside out. Common parasitoids include tiny wasps and flies. They are usually host specific.

•      Predators

Other organisms that eat the pest. Predators are usually not specific about what they eat they will eat a variety of pests.

•      Pathogens

Disease-causing organisms such as bacteria, viruses, and fungi that infect and kill the pest. Environmental conditions such as high humidity or high pest abundance allow naturally occurring pathogens to multiply and cause disease outbreaks (epizootic) that reduce a pest population. Some insect pathogens are manipulated to control specific pests.

For example, the soil bacterium Bacillus thuringiensis (commonly known as Bt) can kill a variety of insects, including many caterpillars and mosquito and beetle larvae.

CHEMICAL CONTROL

•      Chemical control reduces a pest population through the application of pesticides. The decision to use a pesticide as part of an IPM program should be based on a scouting program, pest identification, economic thresholds, and the crop/pest life stage. When used properly, pesticides provide effective and reliable control of most pest species.

TYPES OF PESTICIDES

•      Soil-applied pesticides

–     Chemigation 

                        Applying a pesticide or fertilizer to the soil by injecting it into the irrigation system.

–     Insecticides

Applied to prevent insect damage to the roots of corn and other crops. Insecticides can be applied by broadcast soil applications and soil incorporation before planting, applied in the seed furrow at planting, or broadcast before or after crop emergence

–     Herbicides

Applied to the soil surface and mixed into the soil before planting (pre-plant incorporated) or applied after planting but before crop emergence and not incorporated (pre-emergence).

–     Soil fumigants or nematicides 

Applied to the soil to control nematodes

•      Foliar-applied pesticides

Most foliar applications are broadcast liquid pesticides applied directly to the crop or pest. They can be applied before damage occurs (preventive) or in response to damage (curative).

–     Insecticides

Generally applied to control insects feeding aboveground on the crop.

–     Herbicides

Applied to the weed foliage after the crop and weeds have emerged (post- 
emergence)

–     Fungicides

Can be applied to the crop before the disease appears (protectant) or to remove the disease after it appears (eradicant).

To use pesticides, Check;

•      Pre-harvest interval

The minimum number of days needed between the last pesticide application and harvest. The pre-harvest interval is based partly on how long it takes the pesticide to break down. Observing the pre-harvest interval reduces pesticide residue on the commodity.

•      Residues

The pesticide that remains on the crop after an application. Ideally, a pesticide is present only long enough to kill the pest and then breaks down. Unfortunately, many pesticides do not break down completely before harvest. Therefore, for each pesticide registered for use on a food or feed crop, the EPA sets the amount of acceptable residue permitted on the harvested crop. Harvesting a crop during the pre-harvest interval or applying more pesticide than the label stipulates increases the potential for residues to exceed legal tolerance levels.

•      Reentry interval (REI)

The amount of time required after a pesticide application before a person can reenter afield without personal protective equipment (PPE). The reentry interval prevents unnecessary pesticide exposure. Only workers trained for early entry under the Worker Protection Standards (WPS) and wearing proper PPE may enter a treated area during the reentry interval.

•      Phytotoxicity 

When a pesticide damages the crop to which it is applied. Pesticide drift, excessive rates, mixing incompatible pesticides, and improper calibration can all cause phytotoxicity. For example, cooler weather followed by a period of bright, hot, dry weather can increase the likelihood of plant damage. Even using pesticides in accordance with the label can result in some phytotoxicity. Applying pesticides within recommended rates and following label instructions for mixing and applying help avoid this problem

•      Pesticide resistance—

The genetically acquired ability of an organism to tolerate the toxic effects of a pesticide (for example, malathion-resistant Indian mealmoths, atrazine-resistant common lambsquarter, and ALS-resistant ragweed). Resistance develops from overuse of the same pesticide or from overuse of a class of pesticides with a common mode of action (for example, organophosphates or ALS herbicides). Therefore, it is important to use pesticides only when necessary.

Reference

•      Michigan State University Extension, A Guide for Commercial Applicators Category 1a, Field Crop Pest Management, Extension Bulletin E-2034, April 2001, Page 8-13.