Pests: Types and Categories

• Pests are organisms considered harmful or detrimental to humans and their possessions.
• A pest is an animal or plant whose population density exceeds an unacceptable threshold, resulting in economic damage (Horn, 1988).
• Noxious organisms considered as pests can carry or cause disease or destroy crops.
• The word "pest" comes from the French word "peste" and the Latin word "pestis" meaning plague.
• Organisms should not be considered pests unless proven to be in a given environmental condition.

Four Main Categories of Pests and Types:

• Vertebrate pests include rodents, eels, birds, and reptiles, as well as other mammals.
• Invertebrate pests include insects and mites, as well as mollusks.
• Weeds are also considered pests.
• Diseases caused by pests include fungi, nematodes, oomycetes, viroids, phytoplasma, viruses, and bacteria.

Types and Examples of Pests:

• Rodents: Rice Field Rat (Rattus argentiventer), Asian House Rat (Rattus tanezumi)
• Birds: Eurasian Tree Sparrow (Passer montanus), Chestnut Munia (Lonchura malacca), Scaly-breasted Munia (Lonchura punctulata), White-bellied Munia (Lonchura leucogastra)
• Eel: Rice paddy eel (Monopterus albus)
• Insects: Green leafhopper (Nephotettix virescens), Fall army worm (Spodoptera frugiperda), Cotton aphids (Aphis gossypii)
• Mites: Red spider mite (Tetranychus urticae)
• Mollusks: Golden apple snail (Pomacea canaliculata), Native apple snail (Pomacea maculata)
• Weeds: Saka-saka (Digitaria ciliaris), Dukayang/Pulang Pwet (Echinochloa colona), Antena (Echinochloa crus-galli), Bakis-kisan (Eleusine indica)
• Diseases: Papaya Ringspot Virus (PRSV), Tungro Virus, Cucurbit Aphid-born Yellow Virus/Namamarako

Categories or Types of Pests Based on Diet:

• Monophagous Pest: Restricted to a single species of organism as their food, ex: Yellow stemborer (Scirpophaga incertulas)
• Polyphagous Pest: Feeds on different kinds of species of organisms, ex: Fall armyworm (Spodoptera frugiperda) and Corn earworm (Helicoverpa armigera)

Categories or Types of Pests Based on Occurrence:

• Regular or Continuous Pest: Frequently occurs on a crop and has a close association with it, ex: EFSB on eggplant, FAW on corn, aphids on cotton
• Occasional Pest: Infrequently occurs and has no close association with the crop, ex: Caseworm on rice, Mealybugs on cotton
• Seasonal Pest: Occurs during a particular season every year, for example, rice field rats and Asian house rats on rice during the dry season.
• Persistent Pest: Occurs on the crop throughout the year and is difficult to control.
• Sporadic Pest: Occurs in isolated localities during certain periods, ex: Common armyworm (Mythimna unipuncta), Rice swarming caterpillar (Spodoptera mauritia), and Black armyworm (Spodoptera exempta) in rice in Southeast Asia.

Categories or Types of Pests Based on Level of Infestation:

• Epidemic Pest: Appears in severe form in a localized region during a particular season.
• Endemic Pest: Occurs regularly in a defined area or locality.

Parameters for Pest Population Damage:

• Economic Threshold Level (ETL) is the population density at which control measures should be implemented to prevent an increasing pest population from reaching the ETL, and is always less than EIL.
• Economic Injury Level (EIL) is the lowest population density that will cause economic damage.
• General Equilibrium Population: The average density of a population over a long period, fluctuating due to biotic and abiotic factors with no permanent environmental changes.
• Damage Boundary (DB): The lowest level of damage can be measured.

Categories or Types of Pests Based on Degree of Damage:

• Key Pest: It is the most severe and damaging, often resulting in unacceptable losses and the GEP lies beyond EIL; chemical control only brings the population down below EIL temporarily unless environmental conditions are changed.
• Major Pest: Its GEP lies just a little below the EIL and frequently rises above it, causes significant damage if preventive methods are not done, and needs to be controlled frequently and regularly.
• Minor Pest: GEP lies below both the EIL and the DB, the population may reach EIL and DB and causes significant damage for unusually a short period of time.
• Potential Pest: At present, they inflict minimal damage, but if allowed to become established or their competition is eliminated by chemical control, they become serious pests.
• Negligible Pest: Pests that cause less than 5% of yield loss.
• The status of a pest as major or minor depends on the threshold level set for it.

How an Organism Becomes a Pest

• The organism must: Be suitable to a habitat, have a high breeding rate, and have the opportunity to cause harm to humans