Pest Management & Food Security

• A pest is any organism that damages cultivated plants, attacks plant products, causes a nuisance, or transmits pathogens to plants, humans, or animals.
• Pests include insects, fungi, viruses, nematodes, weeds, rodents, and birds.
• Pest problems have increased with the sophistication of farming, as humans disrupt stable ecosystems.
• Pests damage crops at all stages: in the field, at harvest, during transportation, and in storage.
• Crop pests cause an estimated 30% loss of potential food, feed, and fiber production worldwide each year, equivalent to about US$ 300 million.
• Crop losses from pests range from 5-40% annually.
• Pest management is essential for food security due to the significant impact of pests on crop yields.

Pest Management and Food Insecurity

• Pests are a major constraint to food availability from production to storage.
• Pest management aims to prevent, suppress, or eradicate organisms that harm agriculture.
• Pest management is favored over terms such as "pest control" because it emphasizes an ecological approach.
• "Pest" often refers to invertebrates but should include any organism (pathogen or weed) causing economic or environmental damage.
• Pest management practices are classified based on the approach or method used.

Approaches to Pest Management

• Pest management approaches can be preventative, suppressive, or aimed at eradication.
• Prevention involves actions taken before a pest problem occurs to reduce its likelihood, including chemical and non-chemical methods.
• Suppression involves actions taken after a pest problem is detected to reduce the pest population to an economically low threshold.
• Eradication is the total elimination of a pest from a designated area, often used for new or ravaging pests, but not for established populations over large areas.

Major Techniques in Pest Control

• Pest management methods include chemical, cultural, mechanical, biological, and legal controls.

Cultural Controls

• Cultural controls are modifications to agronomic practices that reduce pest damage, such as timing of planting and harvest, farm sanitation, cover crops, crop rotation, and poly cropping.

Chemical Control

• Pesticides are widely used for quick pest reduction, but dependence on them is unsustainable.
• Pesticide use can eliminate beneficial natural enemies, leading to pest resurgence.
• Over 500 pest species have developed resistance to pesticides.
• Improper pesticide use can cause illness or death in farmers and users.
• Pesticide residues on harvested food can harm consumer health and the environment.
• Pesticides are often expensive and require foreign exchange for importation.
• Dealers often lack training in advising customers on proper pesticide use.
• Users are often inadequately trained and rely on limited information and trial and error.
• Advertising and promotion by manufacturers can lead to overuse of pesticides.

Biological Control (Biopesticides)

• Biopesticides are derived from natural materials such as microbes, animals, plants, and minerals, and include microbial pesticides, biochemical pesticides, and plant extracts.
• Microbial pesticides use microorganisms as active ingredients, targeting specific pests.
• Biochemical pesticides are naturally occurring substances that control pests through non-toxic mechanisms, such as pheromones and scented plant extracts.
• Plant extracts range from unprocessed extracts to refined products.
• Biopesticides are generally less toxic, affect only the target pest, are effective in small quantities, decompose quickly, and reduce pollution.
• Biopesticides can greatly decrease the use of conventional pesticides in Integrated Pest Management (IPM) programs.

Quarantine against Pests (Legal)

• Quarantine controls can prevent the introduction of exotic pests by controlling imported germplasm.
• Failure in quarantine measures has led to serious pest problems, such as those affecting cassava in Africa.

Integrated Pest Management (IPM)

• Integrated Pest Management (IPM) combines several approaches in an ecologically friendly manner, considering the environment and interactions.
• IPM minimizes environmental impact and economic risks.
• IPM reduces reliance on chemical methods by using non-chemical alternatives.
• IPM conserves natural pest-limiting factors, like parasites and predators, and applies chemical controls selectively.
• IPM aims to keep pest populations below economically damaging thresholds by understanding the relationship between pest numbers, damage, and yield.
• IPM is a flexible 'basket' of techniques selected and modified for specific situations, involving farmers in its development.
• Implementation of IPM in developing countries is slow due to poverty, low agricultural outputs, government prioritization, underdeveloped scientific infrastructures, and lack of funding.

Diapause in Insects

• Diapause is a period of suspended or arrested development in insects triggered by environmental cues such as changes in daylight, temperature, or food availability, allowing insects to survive unfavorable conditions.
• Insects survive extreme conditions through diapause, a predetermined period of dormancy that is genetically programmed and involves adaptive physiological changes.
• Environmental cues control when diapause begins and ends, unlike quiescence, which is a period of slowed development triggered directly by environmental conditions.
• Insects with obligatory diapause undergo this period of arrested development at a predetermined point in their life cycle, regardless of environmental conditions.
• Insects with facultative diapause undergo a period of suspended development only when conditions require it for survival.
• Some insects undergo reproductive diapause, which is a suspension of reproductive functions in adult insects.
• Diapause is induced or terminated in response to environmental cues such as changes in the length of daylight, temperature, food quality and availability, moisture, and pH.
• Photoperiod is the most important cue that regulates the start or end of diapause for many insects.
• Changes in temperature can influence the start or end of diapause.
• As the growing season ends, the diminishing quality of their food sources may help trigger a diapause phase in an insect species.
• Diapauses in different developmental stages are distinguished because this appears to be the main divider among modes of regulation, rather than phylogeny.
• The factor controlling embryonic diapause in the silk moth Bombyx mori is a hormone simply called diapause hormone.
• A typical model for induction of larval and pupal diapause involves an axis from the brain to the prothoracic gland.
• A classical model is that adult diapause is induced and maintained by a reduction in JH secretion from the corpora allata (CA).
• Whereas photoperiod is undoubtedly the most important environmental cue that regulates both diapause and production of seasonal morphs, the effects of temperature and diet in modifying this response are very common.
• Diapause helps insects exploit seasonally fluctuating resources, diversifies in tropical habitats, and allows them to colonize temperate and Polar Regions.

Diapause expression in a climate change context

• A better understanding of disruption of seasonal events through climate change is needed.
• Rising temperatures may lead to presence of crop pests throughout winter, as it has already been documented for some aphid species.
• Diapause is under strong endocrine control, and it is possible to inhibit or induce it by exposing insects to various synthetic hormones that mimic natural ones.

Hibernation

• Hibernation is a state in which the body of an organism has the least amount of metabolic activity.
• It is a seasonal state characterized by low body temperature, decreased cardiac activity, and decreased metabolic rate, among other characteristics.
• It causes the body to slow down its respiration, temperature, and other energy-consuming processes.
• It is primarily a body response to a lack of food and a cold environment.

Aestivation

• Aestivation is a state of animal dormancy, characterized by inactivity and a lowered metabolic rate, that is entered in response to high temperatures and arid conditions.
• It takes place during times of heat and dryness.
• It is similar to hibernation, but whereas hibernation is triggered by cold temperatures and reduced food availability, aestivation is triggered by hot temperatures and water scarcity.
• Allows animals to survive in hot and dry environments where food and water are scarce, and it is an important adaptation for many species that live in arid regions.