Module 4: Implementation of IPM
In the previous Modules you have learned a considerable amount about what IPM is (and isn’t), key concepts underlying IPM, and also about the range of preventative, interventive, and regulatory tools used. In this module you will be required to integrate this information and knowledge and use it to design an IPM program for a particular pest and crop. We will introduce a step-by-step approach to implementing IPM on an individual production unit based on research conducted by the University of Delaware.
The 8 steps recommended are:
- Identify Pest(s)
- Determine Pest, Beneficial and Crop Dynamics
- Plan Preventative Strategies
- Monitor Pests
- Decide on Need to Control
- Select Optimal Pest Control Tactics
4.1: Step 1 – Pest Identification
Determining what pests and pest development stages are causing the damage is the foundation of all IPM decision making. Identifying pests, potential pests, neutrals, and beneficials in an agroecosystem can be a daunting task. There are thousands of species of organisms other than the crop in an average field. However, accurate identification is essential for making useful decisions about intervention measures.
Many farmers and agricultural workers make collections of the organisms associated with a particular crop in a particular location. Creating a reference collection helps with future identification tasks and is an excellent way to become acquainted with local biodiversity.
The most commonly encountered groups of pest organisms in a crop field are insects and weeds (plants) and the vast majority of agricultural pests belong to these two groups. Insects and weeds are familiar to most people – most people can tell a butterfly from a grasshopper or a grass from a vine. Learning the most common weed and insect pests for a particular crop in a particular location will address the majority of potential pest problems.
Other groups, such as fungi, nematodes, and viruses are often identified by the symptoms they cause in the crop plant or through laboratory testing. Symptomatic identification of diseases is a useful way of identifying diseases, although it is not as accurate as identifying the actual pest organism. Identification by symptom is further complicated by the fact that plants also exhibit symptoms for non-disease health problems such as stress and nutrient deficiencies/overdoses.
Organisms are scientifically classified using a hierarchical system called taxonomy. If you are not familiar with taxonomic principles, visit this page about binomial nomenclature for a quick review.
4.1.1: Identification of Resources
Most identification resources are in the form of field guides or binomial keys. Computer-based identification keys combine features of both systems. Accurate identification usually involves using binomial keys full of esoteric anatomical terms – not a lot of fun for most people. Field guides and computer-based keys are easier to use but can lead to mistaken identification. Generally, a field guide is a good primary resource for pest identification, with binomial keys used as a backup for tricky identification problems.
Field Guides: Field guides are organized according to organism (e.g. Insects, Grasses), crop (e.g. rice, vegetables), or region. For major commercial crops like rice, field guides showing most of the important pests, weeds, disease symptoms, and stress symptoms are available. For minor crops, a number of different guides and keys may be necessary to properly identify all the potentially encountered pest problems.
Binomial keys: Binomial keys have a much broader coverage than field guides, but they are often obscure and/or difficult to use. Most species that you will ever encounter on cultivated land have likely been identified and described by someone, somewhere, but locating the necessary information is often a daunting task.
Difficult identifications: For hard to identify organisms, a good place to start is the Tree of Life or the herbarium or zoological museum of a local university or government agriculture department. Local collections are more likely to contain the particular organism that you’re interested in. For most groups of organisms, there is an expert somewhere in the world who can probably assist if you come to a dead end.
Local knowledge: Many farmers are quite knowledgeable about the pests in their fields. Ask them what a particular pest is called in the local language, and trace this name back to the species description using bibliographic or taxonomic databases. Indigenous classifications don’t always agree with scientific ones, however – an entire family of insects may all share the same local name, while a single species could have several different descriptive names.
4.2: Step 2 – Determine Pest, Beneficial and Crop (Agroecosystem) Dynamics
Once a pest is identified, the next step is to gather enough information about the biology of the pest encountered to assess the potential risk that the pest poses and determine the best possible management strategy. This information often comes from publications, Extension services, or the Internet, but can also come from firsthand observations of the pest. Similar information should be gathered for beneficials. You can use the scientific name to search for agroecological information about that pest. Usually, resources that use scientific names are more reliable than those that use only common names, although there are exceptions. You should also take a moment or two to ‘learn’ the organism you have just identified so that you can identify it more quickly and easily the next time. Knowing and being able to quickly identify the major pests in a crop field is a definite advantage for IPM work.
Some key questions to answer at this stage include:
- When does the pest inflict injury?
- How much injury is tolerable?
- What are the expected losses if controls are not used?
- What is the most vulnerable stage for management?
- What are the known natural control agents and are they present in the crop?
- What plants does this pest feed on? If a weed, what plants does the weed compete with? If a disease, what plants does it infect?
- Under what conditions does the pest appear? In what habitat does the pest lay its eggs, build its nest, etc. If a weed or a disease, how is it propagated?
- How does the pest survive between crops?
- What are the natural controls of this pest?
- What interventions are effective against this pest?
- How can the cropping system be altered to make life more difficult for the pest and easier for its natural controls?
4.3: Step 3 – Plan/Assess Preventative Strategies
We have already noted that prevention is the preferred management strategy in IPM. Prevention starts with a careful examination of field history and all aspects of the crop production system to determine if the crop can be grown or treated to prevent pest populations from exceeding economic levels. Questions to answer at this stage include:
- Can any cropping practice, such as time of planting, crop rotation, or tillage, be manipulated to reduce pest attack?
- Are the chances of economic pest losses great enough to justify a preventative pesticide strategy?
- What are the existing natural control agents that can be augmented or conserved?
4.4: Step 4 – Monitor
Monitoring involves periodic assessment and recording of pests, natural control factors, crop characteristics, and environmental factors. Different methods and sampling frequencies are used, depending on the type of pest and monitoring objective. Monitoring involves direct and indirect means – field scouting to make visual counts or assessment of damage, or the use of trapping devices (pheromone traps, light traps).
4.4.1 Determining Pest/Beneficial Population Densities
The best way to determine population densities is by calculating the density in a few sample areas and then extrapolating this to represent the entire field.
Sampling involves several steps. These include
- Pre-determining the sampling pattern.
- Locating the sample units in the field.
- Trapping, capturing, counting, and recording the numbers of organisms in the sample plot.
- Extrapolating these numbers to arrive at an estimate for the whole field.
It is important to use a consistent sampling method from one observation period to the next. Using different methods can make the data from different observations inconsistent and therefore useless.
4.4.2 Determining Crop Condition and Characteristics
Assessment of the crop itself is the second major component of monitoring. The health and growth stage of the crop should be regularly observed. In particular, damage and disease symptoms should be noted. Important features to look for in the crop can include
- leaf counts
- leaf colour analysis
- damage to plant parts
- withering or wilting
- growth stage (tillering, flowering, etc.)
- abnormalities such as spots, bumps, discoloration, etc
- leaf nutrient assays
- disease assays
Many of these characteristics can be observed directly, but some, such as leaf nutrient assays and disease tests, require off-farm analysis in government or private laboratories.
It is important to keep accurate records of ALL observations made in an IPM program. Seemingly trivial notes about a newly observed pest or a strangely coloured leaf could be the key to proper diagnosis and treatment of a major pest problem. Having a systematic way of noting and recording information assures that important details are not lost.
The key to being able to use your observations is a robust record-keeping system and several have been developed for keeping track of IPM observations. IPM is notable for the diversity of approaches taken by practitioners, and it is likely that most IPM record-keeping systems will contain some unique features. The important thing is that the system is easy to use, captures all the necessary information, and is used consistently from one observation to the next.
4.5: Step 5 – Decision Making
Decision making involves an evaluation of the monitoring information collected in the last step to assess the relevant economic benefits versus the risks of pest management actions. Questions to answer include:
- What will I lose if I do nothing? What will I gain?
- Are there enough natural control agents present to reduce the pest population below economic levels?
- Is the damage potential of the pest more costly than the control?
Answering these questions is usually done by comparing estimates of pest population size to the previously discussed “economic thresholds” or “action thresholds” (see Lessons 2.2.1 – 2.2.4 for a review of the Economic Threshold concept). These serve as references for loss potential at particular crop growth stages or sets of crop conditions.
4.6: Step 6 – Select Optimal Pest Control Tactics
If a decision is made to intervene, tools have to be selected that will adequately manage the problem while minimizing economic, health and environmental risks. Key questions to answer when selecting control tactics include:
- Are there opportunities to integrate nonchemical tactics?
- How well will the control option fit into the total management system?
- How well will the tactic control the pest? What effects will this action have on the user, society as a whole, and the environment?
- Will this action impact, either positively or negatively, the other insect pest species or natural enemies present in my crop?
For chemical controls, important questions at this step are:
- What is the best insecticide for the target pest?
- What is the optimal rate?
- Is it legal?
- What are the safety requirements and use restrictions?
Some considerations associated with selecting and recommending tactics in a broader IPM program (not just for an individual plot or field) are that these tactics need to integrate with three components of a farming community to be successful. The 3 components are:
- Available IPM methods. IPM implementation needs to bring together all the various prevention, observation, decision, and intervention methods that are available to the farmer. This list can include methods that farmers already use and are familiar with, as well as novel methods and techniques that would fit well into the local system. New methods must be chosen carefully so that they are not beyond locally available resources.
- Cropping system/agroecosystem. The IPM program needs to be compatible with the cropping system and the agroecosystem. IPM recommendations for one crop that interfere with another traditional crop are unlikely to be adopted. Intercropping a corn crop with beans will only be adopted if the farmer likes eating (or can sell) the beans! This may seem obvious, but it is surprising how many times simple considerations like this are overlooked.
- Community health. IPM needs to consider the health of the community. IPM generally, but not always, can improve the health of farming communities through improved profits and reduced exposure to pesticides. However, IPM isn’t always better. For example, what if reduced pesticide use results in increased labour requirements and children who should otherwise be in school provide that labour? Or what if a using a lower-risk biopesticide like rotenone impacts the local fishery? All of the potential impacts of an IPM program need to be considered if an IPM program is to be a success.
4.7: Step 7 – Implementation
Once the interventions are selected, they should be deployed on a timely manner with precision and completeness. When intervening with a chemical pesticide it is critical to remember that proper timing and placement is often more important than the rate. Key questions to answer during this step include:
- What can be done to improve effectiveness of the management tactics?
- Is the pesticide application equipment calibrated properly and in good working condition?
- If pesticides are used, what is the appropriate chemical and rate for the target pest?
- Can the pesticide be applied in a manner that will be least disruptive on natural enemies while still provide effective control?
- In certain situations, it may be desirable to leave small non-treated areas to evaluate control effectiveness.
4.8: Step 8 – Evaluation
When implementing an IPM program you should always take time to follow-up and evaluate pest control actions to determine if you got your money’s worth. Review what went wrong but more importantly what went right.
- Was the choice of control action appropriate?
- Was the management action implemented on time and according to recommendations?
- What changes to the management tactics can be made to improve control if the same pest problem occurs in the future?
- What future changes in the production system can be made to achieve more permanent suppression of the pest problem?