When people discuss food processing pest management, discussion usually concerns a crisis point or another area where a problem has erupted and people are trying to solve the problem. Most concerns revolve around concern from governmental and regulatory enforcement actions or consumer complaints. The biggest impediment to improved management and implementation of IPM systems is the prevailing attitude of eradication. While managers of other commodities such as fresh market produce have accepted IPM principles, the food processing and distribution system
has not yet accepted the philosophy behind this system.
IPM is defined as a systematic approach to commodity protection emphasizing increased information for improved decision making to reduce purchased inputs and optimize social, economic and environmental consequences. The IPM concept emphasizes integration of disciplines and control measures into a total management system. Control or management measures include natural enemies, cultural management, temperature and other physical controls, sanitation and pesticides. This system anticipates and prevents pests from reaching damaging levels and improves overall economic and social outcomes. From an economic and ecological standpoint, IPM is based on the “economic threshold” concept that management action is taken only when potential losses due
to pest populations exceed costs of controls available to reduce the populations.
Basic changes in management decision making processes are required to implement an effective IPM program. Food processors and distributors must realize most decisions have consequences far beyond a particular time period and location. Excessive use of management practices such as pesticides may reduce profitability, create potential worker hazards and stimulate pesticide resistance. Keys to implementing IPM include understanding factors that regulate systems, monitoring, maintaining good records and using this information to make sound management decisions.
Postharvest systems are regulated by moisture content, temperature, pest access and time that the product is in a susceptible state. Within biological limits, the greater the temperature, moisture content and the time products are in a susceptible condition, the higher the resultant pest population. Management systems must be built around these biological and management factors and
their influence on population dynamics.
Different insect and mold species have different requirements for grain moisture. The rice weevil is limited by its requirements for high grain moisture (>13%), whereas the lesser grain borer can tolerate dry grain. Within limits, the greater the moisture content, the higher population growth. Mold growth normally requires high grain moisture greater than 14-15%. Most processed goods are low in moisture content, and this helps reduce population development.
Temperature is the most important regulatory property in processed food storage. Temperatures below 65°F are unfavorable for insects and molds. Likewise, grain temperatures above 95°F are unfavorable for insects. Insects are especially sensitive to high temperature, and high temperatures have been used as a disinfestation and management practices for centuries. From a stored product management viewpoint, keeping insects at sub-optimal temperatures is important to reduce population development and minimize damage and cosmetic concerns. The interaction of both temperature and time to achieve mortality are obvious. Even relatively low temperatures can be very effective in suppressing insect populations.
A key component is that insects are very durable creatures and, if insects are given time to adjust to changing temperatures, insects will modify their physiology to survive extended periods of harsh temperatures. This is primarily true for cold temperatures. However, if the temperature change is rapid and dramatic (e.g., taking insects from 90°F to 60°F), very high mortality will occur.
Different insect species have differing tolerances and temperatures that are optimal. Insects most sensitive to cold are red and confused flour beetles. The most cold tolerant are the weevils and the Indian meal moth. The stage of development can also help insects survive harsh climates. For example, larvae of the lesser grain borer and rice weevil are very cold tolerant, whereas adults of the rusty and red flour beetles are the most cold tolerant.
Surrounding conditions have a significant influence on insects. Earlier discussion demonstrated the significant impact commodity moisture could have on population development. Likewise, relative humidity has a significant impact on insect mortality in different temperatures.
Stored grain insects and molds are very predictable and have an exponential growth curve after the product is processed. Managers have the ability to shift this population curve to the right or to the left and the magnitude of the height depending on their sanitation program and the ability to aerate to control temperature.
Most stored product insects can fly and move within and between storage structures. Maintenance sanitation and residual sprays are keys to minimizing residual populations in storage facilities and reducing the population growth of insects. Food warehouse facilities are very attractive to stored product insects and insects will find these facilities. Keeping insect movement to a minimum is a key component to sound management.
Carefully inspect all materials entering a warehouse area. This should include raw products, paper materials, packaging or any other material that could transport insects.
Design storage and processing areas to minimize open areas, unscreened vents and other areas of access.
Screen all vents, doors and other areas to minimize access. Use fine mesh screens to minimize penetration.
Make sure doors are not left open, and it is preferable to have double doors to minimize migration.
If a significant infestation is found, eliminate the population to prevent spread and modify microclimate to prevent insects from developing significant populations.
The backbone of any management system is effectively sampling pest populations and monitoring grain/product quality. There has been a great deal of excitement regarding new sampling tools that have become available for insect sampling in grains, warehouses and processing facilities. These tools can be pheromone baited or used unbaited. These sampling tools have not been accepted because they are presently uncalibrated and there is no implementation work demonstrating these in commercial situations. In processing industries, trapping systems are of great assistance in
detection to maintain low populations of insects.
Visual inspection can be a key to maintain a low population in food processing and food warehouses. Key areas to watch are foods that are high risk:
Visual inspections also have another added benefit – they force personnel to walk through a facility and notice any open packages, improper sanitation and other areas that will attract and allow a population of insects to develop.
Lights are often an excellent place to begin a facility inspection. Most stored product insects are attracted to lights. If Indian meal moths or other insects are noticed flying around lights, there is likely a population within the warehouse. Indian meal moths were often thought to avoid light; however, they are significantly attracted to light and this is a good way to initially sample for Indian meal moth adults. Replacing incandescent or mercury vapor light with yellow or sodium arc lights at outdoor areas can be effective in reducing the attraction of insects from outside services.
For each insect and sampling requirement, the user must decide what kind of trap and if there are needs for attractants.
A pheromone is a chemical attractant released by an insect to affect the behavior of the same species of insect. Two commonly used pheromones for insects are sex and aggregation pheromones.
Sex pheromones are used to facilitate mate location and mating. There are several commercially available sex pheromones for use in traps to improve sampling. Most commonly used is the
Indian meal moth pheromone.
Aggregation pheromones are chemical substances released to attract members of the same species. The most commonly used is the confused flour beetle pheromone.
Food attractants are often used in corrugated traps and have significant advantages because the food attracts all species of food-processing insects. An obvious limitation to the use of food attractant in a food warehouse is the competition with food odors surrounding the traps.
With decreased pesticide alternatives and increased regulations, the processing industry will have to begin looking for alternatives to pesticides. These alternatives will have to be based on the ecology of the system with an emphasis on system regulatory mechanisms. Many flourmills are beginning to use heat treatments to manage insect populations. Management options should emphasize available tools such as hot or cold temperature manipulation, improved monitoring systems in processing, increased awareness of sanitation and housekeeping and having well trained
personnel throughout the system from acquisition to marketing.
A tool to determine the presence or absence of potentially harmful pest insects is needed where stored commodities are held for extended lengths of time. Pheromone-baited traps are excellent tools for this purpose.
Trapping systems are significant tools to use in an integrated pest management program in warehouses. Pheromone-baited traps can be used in a variety of ways to assist in a warehouse pest management program:
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