Common Types and Species of Pests in Kenya

Common Types and Species of Pests in Kenya

A pest is classed as an animal which could be harmful to humans. They may for example damage crops, livestock or forestry, cause a nuisance by invading homes and work spaces or cause illness by spreading disease

ANTS, BEES AND WASPS

Ant, wasps, bees and ants collectively known as hymenopterods are one of the largest orders of insects. There are over 130,000 species described with many others remaining to be. It is yet unknown how many species exist in the world as new species are found frequently but a very rough estimate from local literature indicates that till 1995 over 178 species comprising of 113 species of wasps, 46 species of bees and around 52 species of ants were already known locally.

Females typically have a special ovipositor for inserting eggs into hosts or otherwise inaccessible places. The ovipositor is often modified into a stinger. The young develop through complete metamorphosis i.e. they have a worm-like larval stage and an inactive pupal stage before they mature.

Although many species (types of pests in Kenya) are regarded as domestic pests, nearly none have proved to be an actual pest (e.g. carrying disease, etc) but their persistence in numbers is generally regarded as a nuisance to the owner of infested facility.

BED BUGS

Bedbugs are small, elusive, and parasitic organisms all belonging to a family of insects called Cimicidae. They live strictly by feeding on the blood of humans and other warm-blooded animals (such as other mammals and birds). The name ‘bed bug’ is derived from the insect’s preferred habitat, infesting houses and especially beds or other common areas where people may sleep. These insects may also be found on carpets and other areas where host is present. Bedbugs, though not strictly nocturnal, are mainly active at night and are capable of feeding on their hosts without being noticed. The number of species of bedbugs has been estimated to be anywhere between 75 and 108. Most species only feed on humans when other prey is unavailable. In Malta the species number is yet unknown but the most cosmopolitan species are presumed present. The only species currently recorded locally is Cimex lectularius. The latter is mostly found in hotels but recently populations have exploded and several cases were reported from private homes. Adult bedbugs are reddish-brown, flattened, oval, and wingless. Bedbugs have microscopic hairs that give them a banded appearance. A common misconception is that they are not visible to the naked eye. Adults grow to 4–5 mm in length and 1.5–3 mm in width. The life span of bedbugs varies by species and is also dependent on feeding. Bedbugs are bloodsucking insects. They are normally out at night just before dawn, with a peak feeding period of about an hour before sunrise. Bedbugs may attempt to feed at other times if given the opportunity and have been observed feeding during all periods of the day. They reach their host by walking, or sometimes climb the walls to the ceiling and drop down on feeling a heat wave. Bedbugs are attracted to their hosts by warmth and the presence of carbon dioxide. The bug pierces the skin of its host with two hollow feeding tubes. With one tube it injects its saliva, which contains anticoagulants (so blood will not clot) and anesthetics (so you don’t feel them), while with the other it withdraws the blood of its host. After feeding for about five minutes, the bug returns to its hiding place. The bites cannot usually be felt until some minutes or hours later, as a dermatological reaction to the injected agents, and the first indication of a bite usually comes from the desire to scratch the bite site. Due to their natural aversion for sunlight, bedbugs come out at night.

COCKROACHES

This order of insects, scientifically known as Blattaria, consists of around 4,000 species worldwide, of which 30 species are associated with human habitations and about 4 species are well known as pests (types of pests in Kenya).

Although worldwide these insects have a bad reputation, many cockroaches live in warm, tropical areas and feed on decaying wood and leaves. They help break down this organic debris; in the process, they add nutrients to the soil through their waste. They’re also a food source for small reptiles and mammals. In other words, cockroaches are ¬an important part of many ecosystems.

In fact, in many parts of the world, just one or two species are responsible for most infestations. Unfortunately, people take much of the blame for this worldwide prevalence. Most cockroach pests have spread across the planet by hitchhiking on boats, airplanes, trucks and even in moving boxes and grocery bags.

Cockroaches live in a wide range of environments around the world. Pest species of cockroaches adapt readily to a variety of environments, but prefer warm conditions found within buildings.

Female cockroaches are sometimes seen carrying egg cases on the end of their abdomen; the egg case of most cockroach species holds about 30 to 40 long, thin eggs, packed like frankfurters in the case called an ootheca. The eggs hatch from the combined pressure of the hatchlings gulping air and are initially bright white nymphs (young) that continue inflating themselves with air, becoming harder and darker within about four hours. Their transient white stage while hatching and later while molting (shedding their outer skin) has led to many claims of glimpses of an albino cockroach. Locally it is believed that the “white roach” is a separate super species that lives only underground and commands other cockroach species to do the jobs for them. An example is getting them food and cleaning them. This is obviously a myth. We also have a tendency to distinguish all cockroach nymphs and smaller species by referring to them.

The latter two are never met in households as one is restricted to one locality and the other is restricted to garigue habitat. The Oriental, Brown-banded and Egyptian roaches are rarely met with as they prefer human disturbed areas but away from them. The latter might be attracted to a very dusty area such an abandoned garage but it is harmless and females are easily consumed by very large woodlice and males are confused with moths. Other species are also locally being discovered.

On the other hand the American and German cockroaches can be very loyal to our houses especially our kitchens and these are the ones that should be treated as pests

The American cockroach generally lives in moist areas, but can survive in dry areas if they have access to water. The members of this species prefer warm temperatures around 28-32 degrees Celcius and do not tolerate very cold temperatures. In residential areas, these cockroaches live in kitchens, basements and sewers, and may move outdoors during warm weather. They have been known to fly during mating season. To aid its resistance the latter is also scavenger that feeds on decaying organic matter and a variety of other foods. It is particularly fond of fermenting foods. Females produce egg cases and carry them protruding from the tip of the abdomen for about two days. Egg cases are then generally placed on a surface in a hidden location. Egg cases are about 0.9 centimeters long, brown, and purse shaped. Immature cockroaches emerge from egg cases in 6 to 8 weeks and require 6 to 12 months to mature. Adult cockroaches can live up to one year, during which females produce an average of 150 young. Despite its name this species originated from Africa and was spread through human agency.

The German cockroach, is a small species, measuring between 1.3 centimeters and 1.6 centimeters long; however, they are known to get bigger. It can be tan through brown to almost black, and has two dark parallel streaks running from the head to the base of the wings. Although it has wings, it is unable to sustain flight.

A female of this species carries an egg capsule containing around 40 eggs. She drops the capsule prior to hatching, though live births do rarely occur. Development from eggs to adults takes 3 to 4 months. Cockroaches live up to a year. The female may produce up to eight egg cases in a lifetime; in favorable conditions, it can produce 300 to 400 offspring. Other species of cockroach, however, can produce an extremely high number of eggs in a lifetime, but in some cases the female needs to be impregnated only once to be able to lay eggs for the rest of her life.

FLEAS

Flea is the common name for insects of the order Siphonaptera, which are wingless insects with mouthparts adapted for piercing skin and sucking blood. Fleas are external parasites, living on the blood of mammals (including humans) and birds. In the past, it was most commonly thought that fleas had evolved from the flies (Diptera), (types of pests in Kenya) based on similarities of the larvae. Now it is more certain that they are descendants of the snow scorpion-flies, family Boreidae, which are also flightless. There are around 2000 species of fleas known worldwide and the number of local species is yet to be determined.

Their legs are long, the hind pair well adapted for jumping vertically up to 18 cm and horizontally up to 33 cm on average. This is around 200 times their own body length, making the flea one of the best jumpers of all known animals (in comparison to body size), second only to the froghopper. Their bodies are laterally compressed, permitting easy movement through the hairs or feathers on the host’s body (or in the case of humans, under clothing). The flea body is hard, polished, and covered with many hairs and short spines directed backwards, which also assist its movements on the host. The tough body is able to withstand great pressure, likely an adaptation to survive attempts of eliminating them, such as mashing and scratching. Even hard squeezing between the fingers is normally insufficient to kill a flea.

Once the flea reaches adulthood, its primary goal is to find blood as it is the only diet for adult fleas. Adult fleas only have around a week to find food once they emerge, though they can withstand between two months and a year between meals. A flea population is unevenly distributed, with 50 percent eggs, 35 percent larvae, 10 percent pupae, and 5 percent adults. Their total life cycle can take as little as two weeks, but may be lengthened to many months if conditions are favourable. Female fleas can lay 500 or more eggs throughout their lives. Adaptations can be clearly observed in Rabbit Fleas (Spilopsyllus cuniculi) Bergħud tal-Fniek. Fleas attack a wide variety of warm-blooded vertebrates including dogs, cats, mice, chickens, rabbits, squirrels, rats, ferrets, and humans. The most common species include Cat Flea (Ctenocephalides felis) Bergħud tal-Qtates. The primary host of this species is the domestic cat, but this is also the primary flea which infests dogs in most of the world. The cat flea can also maintain its life cycle on rabbits, rodents, ruminants and humans, but a population of cat fleas cannot be sustained by these aberrant hosts. The Dog Flea (Ctenocephalides canis) Bergħud tal-Klieb, is very similar in habit to the cat flea but it is more commonly found in Europe. On the other hand, the Human Flea (Pulex irritans) Bergħud tal-Bniedem, is a cosmopolitan flea species that has, in spite of the common name, a wide host spectrum. Besides the problems posed by the creature itself, fleas can also act as a vector for disease. A very famous example is the Black Death, which killed millions of people in Europe during the middle ages, because of a flea species which was common on Black Rats, which acted as a vector for the bacterium Yersinia pestis.

FLIES

The true flies are insects, scientifically known as Diptera which means two-winged species. This large group consists of around 120,000 species worldwide but it is believed that more of the same amount are still not described. It is one of the major insect orders in terms of both ecological and human (medical and economic) importance. While the majority is beneficial and of great importance to their local ecosystems only a dozen or so species are associated with human habitations while about a handful species are well known as pests. It is yet unknown how many species exist in the Maltese Islands as new species are found frequently but a very rough estimate from local literature indicates that till 1995 over 218 species were already known locally. Others have been recorded since. These endemic species include the Schembri’s Spider Fly (Ogcodes schembrii) Dubbiena tal-Brimb ta’ Schembri.

Flies are well adapted for aerial movement, and typically have short and streamlined bodies. They have a mobile head with eyes, and, in most cases, have large compound eyes on the sides of the head, with five small ocelli on the top area. The antennae take a variety of forms, but are often short, to reduce drag while flying. Flies consume only liquid food, and their mouthparts and digestive tract show various modifications for this diet. The majority of species spit out saliva on solid foods to predigest it, and then suck the external semi-digested material back in. They also regurgitate partly digested matter and pass it again to the abdomen. The most apparently primitive flies have piercing blade-like mandibles and fleshy palps, but these have developed into numerous different adaptive forms in different groups. These include both the fine stilleto-like sucking mouthparts of mosquitoes, and the fleshy proboscis of houseflies. The gut typically includes large diverticulae (outpouchings of a hollow or a fluid filled structure) allowing the insect to store small quantities of liquid after a meal.

The female lays her eggs as close to the food source as possible and development is generally rapid, allowing the larva to consume as much food as possible in a short period of time before transforming into the adult. In extreme cases, the eggs hatch immediately after being laid, while a few flies are ovoviviparous, (bear live young) with the larva hatching inside the mother

Species like the House, Blue, Green and Flesh flies can be very loyal to our establishments and these are the ones that should be treated as pests. As a world wide perspective Diptera, in particular the mosquitoes (Culicidae), are of great importance in disease transmitters, acting as vectors for malaria, dengue, West Nile virus, yellow fever, encephalitis and other infectious diseases.

MYRIAPODS

Myriapoda is a group (subphylum) of arthropods (which also includes insects, arachnids and crustaceans) containing millipedes, centipedes, and others. The group has 13,000 known species, all of which are terrestrial (land dwellers). Although their name suggests they have myriad (10,000) legs, myriapods range from having over 750 in some species to others having fewer than ten legs. Around 15 species of millipedes are known to occur locally. The most common home encounter is the Common Millipede Pachyiulus flavipes Ħanex tal-Indewwa/Tad-Djar, which is found in most local establishments where a high level of humidity persists. They can be handled, and are quite docile and slow moving. This species, like most, has two main modes of defense used by its members if they feel threatened: curling into a tight spiral exposing only the hard exoskeleton, and secretion of an irritating liquid from pores in their body wall. Centipedes make up the order Chilopoda. They are fast, predatory and venomous, hunting mostly at night. There are around 3,300 species. They range from species not exceeding 12 mm to others which may exceed 30 cm. About 16 species have been recorded in the Maltese islands. Although not generally considered dangerous to humans, many myriapods produce noxious secretions which can cause temporary blistering and discoloration of the skin.

PIGEONS

Locally, the only species of birds that are usually considered as agricultural pests are the following three: the Spanish Sparrow (Passer hispaniolensis), Għasfur or Għammiel tal-Bejt, is usually considered a pest in fields as it gathers in large numbers to feed on agricultural products. It easily gets familiar to objects installed primarily to scare it. In fact local farmers tend to nick name it as ‘ġurdien bil- ġwienaħ’ (mouse with wings), and this is because of the latter’s destructions and also due to its cunningness of a mouse. The only nuisance caused by this bird as a domestic pest is that it tends to see ventilators as the cradle for its offspring. Besides the nest which sometimes makes a foul smell, arthropods usually follow within it. Nest material tends to be bulky, blocks the ventilator and nest material starts entering the house. Despite all this, it is illegal to disturb in any way this species, because it is protected by law. Nearly the same applies for the Starling (Sturnus vulgaris ) Sturnell, except that it does not breed in ventilators and that in some time of the year it may be legally recognized as a huntable species.

On the other hand the Feral pigeon is considered to be both an agricultural and domestic pest, and most tend to blame the latter for fouling most facades of buildings within towns and cities and for carrying certain diseases. As agricultural pests, they eat adequate quantities of agricultural products, and they tend to spread diseases from one farm to the other.

Pigeons have been falsely associated with the spreading of human diseases. Contact with pigeon droppings poses a minor risk of contracting histoplasmosis, cryptococcosis, and psittacosis. Pigeons are, however, at potential risk of carrying and spreading avian influenza. Although one study has shown that adult pigeons are not clinically susceptible to the most dangerous strain of avian influenza, the H5N1, other studies have presented definitive evidence of clinical signs and neurological lesions resulting from infection. Furthermore, it has been shown that pigeons are susceptible to other strains of avian influenza, such as the H7N7, from which at least one human fatality has been recorded.

RODENTS

Rodentia is an order of mammals also known as rodents, characterized by two continuously growing incisors (front teeth), two on the upper and lower jaws respectively, which must be kept short by gnawing. This is the origin of the name, from the Latin word rodere, which means to gnaw. These teeth are used for cutting wood, biting through the skin of fruit, or for defense. The teeth have enamel on the outside and exposed dentine on the inside, so they self-sharpen during gnawing. Rodents lack canines, and have a space between their incisors and premolars.

Forty percent of mammal species world-wide are rodents (around 2,277 species). They are found in vast numbers present nearly on all continents and islands, and in all habitats except oceans and Antarctica. Their success is probably due to their small size, short breeding cycle, and ability to gnaw and feed on a wide variety of foods.

Rodents are important in many ecosystems because they reproduce rapidly, and can function as food sources for predators, mechanisms for seed dispersal, and as disease vectors. Humans use rodents as a source of fur, as pets, as model organisms in animal testing, for food, and even for detecting landmines.

In the Maltese Islands four species of rodents are known to occur. These are divided in 2 species of rats and 2 species of mice. Rats are typically distinguished from mice by their size; rats are generally large rodents, while mice are smaller. The best-known rat species (and these are what we have in our islands) are the Black Rat (Rattus rattus) and the Brown Rat (Rattus norvegicus). The group is generally known as the Old World rats or true rats, and originated in Asia. Rats are bigger than most Old World mice, which are their relatives, but seldom weigh over 500 grams in the wild. Male rats are generally called bucks, unmated females are called does, pregnant or parent females are called dams, and infants are called kittens or pups. A group of rats is either referred to as a pack or a mischief.

These common species are opportunistic survivors and often live with and near humans, therefore they are known as commensals. They may cause substantial food losses, especially in developing countries. Wild rats and mice can carry many different “zoonotic” pathogens, such as Leptospira, Toxoplasma gondii and Campylobacter, and may transfer them to other species, for example to humans. The Black Death is traditionally believed to have been caused by the micro-organism Yersinia pestis, carried by the Tropical Rat Flea (Xenopsylla cheopis) which parasitized on the Black Rat living in European cities during the epidemic outbreaks of the Middle Ages; these rats were used as transport hosts. Today, this cycle still exists in many countries of the world and plague outbreaks still occur every year. Besides transmitting zoonotic pathogens, rats are also linked to the spread of contagious animal pathogens that may result in livestock diseases such as Classical Swine Fever and Foot-and-mouth disease. The normal lifespan of rats ranges from two to five years, and is typically three years.

Regarding mice, we have two species: the Wood Mouse (Apodemus sylvaticus) and the House Mouse (Mus musculus). The latter thrives under a variety of conditions: they are found in and around homes and commercial outlets as well as in open fields and agricultural lands. House mice consume and contaminate food meant for humans, pets, livestock, or other animals. In addition, they often cause considerable damage to structures and property. They can transmit pathogens that cause diseases such as salmonellosis, a form of food poisoning.

Mice are afraid of rats, which often kill and (partially) eat them. This rat behaviour is known as muricide. Despite this behaviour, free-living populations of rats and mice do exist together locally. House mice are generally poor competitors and cannot survive away from human settlements in areas where other small mammals, such as wood mice, are present.

SNAILS

Molluscs are a category of invertebrates (organisms with no backbone) that possess a soft body as well as a shell. The shell may be either internal or external. Molluscs come in various shapes and sizes and are capable of living anywhere. Only snails and slugs, however, live on land. Land slugs may have an internal shell or no shell at all, therefore they are susceptible to drought and predators, and thus most species in the Mediterranean are cave dwellers or nocturnal to avoid the heat of the day, and unpalatable or poisonous to avoid being eaten. Land slugs are generally found near decaying plant matter or in the soil where it is most moist. Land snails afford to be more versatile regarding where they can live due to their prominent shell. Land snails, like slugs, need moist environments to be active, and tend to be more edible to non-arthropod predators, but they can survive drought in aestivation mode due to their shells, even in exposed areas like dry tall twigs where slugs do not dare to venture. Snails and slugs are collectively known as gastropods. These slow-moving molluscs, snails being the faster of the two, are all hermaphrodite, meaning that each one is both male and female. Therefore, when gastropods copulate, both individuals get pregnant and lay eggs.

Being slow organisms may not make them very dispersive, but their reproductive biology ensures that some species will remain plenty in number, and this is why some have become agricultural and horticultural pests. Locally there roughly 60 species of terrestrial gastropods, most are rare and very small, localized in natural habitats, seldom seen, some are frequent, some are endemic. Only the very few common ones often do damage to crops, or are seen as unwanted guests in households. The largest and most common of the snails is the Edible Snail, which is the also collected in large numbers as a food delicacy. Other smaller but common species are the Red-banded Snail, the Goat Snail. These species are all herbivorous and detritivores, therefore all might resort to eating leafy material in gardens, but the most voracious remains the Edible Snail.

BATS

Bats: With hair and they tend to have rather large ears. Bats use their ears to help them detect the location of objects around them or to locate insects flying through the air. Depending on the species, an adult bat can weigh less than 1 oz. up to 3 lbs. Bats have two wings, consisting of a double membrane stretched across their elongated fingers and arm bones, which are their primary way of getting around. They have four limbs, two legs and two arms with the same bones as human hands modified as part of their wings.

Another interesting bat fact is they are the only mammal capable of true flight. The surface of a bat’s wing is equipped with bumps called “Merkel cells”. These bumps have tiny hairs that help sense airflow during flight so the bat can make adjustments for maximum flight efficiency.

Bat Control

Bat-proofing a structure is the best way to prevent an infestation and the best time to bat-proof is after bats have left for their hibernation periods in the autumn. Attempting to bat-proof at any other time raises the possibility of boxing in babies who will then look for other parts of the house to escape to. At dusk, homeowners should inspect the exterior of the home and observe where bats enter and exit. Common access points include attic louvers and under facia boards. It is recommended that homeowners seal any cracks or crevices with caulk and steel wool. Pay special attention to holes in the structure that lead to dark secluded areas, like attics and belfries. Also, screen attic vents and openings to chimneys, and install door sweeps. Exclusion is the only method to keep bats out long term.

Habits

Most bats leave their roosts at dusk and return around dawn. When traveling, they first stop at a stream or pond for a drink of water before feeding. Female bats of most species tend to only reproduce one pup, but some species can give birth to two to four pups. At birth, a baby bat weighs up to 25 percent of its mother’s weight. While young bats are taken care of by females in the colony, male bats do not contribute to the caring of the babies.

Bats are a very important part of the pollination process, as they feed on insects that visit flowers and also feed on various types of fruit that helps disperse seeds. Since many bats do feed on insects, they can help keep pest insect populations down.

A few common bat species worldwide are the big brown bat, the little brown bat, and the Mexican free-tailed bat.

Big brown bats: A female big brown bat will form her nursery colony with other pregnant females in the spring while the male roosts somewhere else, usually alone or with other males. These bats can become an issue around the home, as they commonly build colonies in attics and shutters. Big brown bats feed on insects like beetles, ants and flies. This species is able to fly up to 40 miles per hour, the fastest flight speed reported for any bat. When migrating, big brown bats travel short distances and hibernate in small groups in hollow trees, caves and buildings.

These bats are dark in color with a pale colored stomach. They have no fur on their wings and have 32 small teeth for feeding. Big brown bats are commonly found everywhere.

Little brown bats: One little brown bat can catch up to 600 mosquitoes in an hour. They alternate feeding flights with rest periods, where they return to their nests to digest their meals. Unlike the big brown bat, this species’ flying habits are erratic, with flight speeds averaging 12.4 miles per hour. Female little brown bats will form nurseries in the spring after hibernating throughout the fall and winter months.

Little brown bats tend to vary in color and have 38 teeth. They can be found worldwide.

Mexican free-tailed bats: These bats usually live-in larger colonies and are raised by the females. They can typically fly at about 10-15 miles per hour but can reach speeds of up to 25 miles per hour. If needed, Mexican free-tailed bats will fly up to 50-150 miles in a day to find food. Moths tend to be the favorite meal of the Mexican free-tailed bat, but they will eat other insects like ants and beetles. They can eat up to ⅓ of their body weight.

Mexican free-tailed bats build their colonies based on where they are located. They can build colonies in structures, such as houses or churches, but can also opt to live inside caves.

Threats

A big concern most homeowners have is whether or not the bats infesting their home have rabies. Unfortunately, it is impossible to tell if the bats have rabies solely based on appearance, so testing must be conducted. If transferred, rabies is a deadly disease that causes inflammation of the brain and sometimes death. However, bats are rarely rabid, with only less than 10 percent documented of becoming rabid.

In addition to the threat of rabies, the fungi that harbor in bat droppings can cause a lung disease known as histoplasmosis. An accumulation of droppings should be professionally decontaminated and removed.

Aside from affecting human health, bat droppings can also damage the home. One bat can produce between 20-30 droppings a day. Because bats typically colonize in large groups, the number of droppings in a home can easily pile up and cause roofs to cave in. Their waste also attracts other pests like cockroaches, and the smell of their feces encourages other bats to invade the home.

Bats can pose a serious health threat to humans if they are found inside a structure. Fungi that harbor in bat droppings can cause the lung disease, histoplasmosis. An accumulation of droppings should be professionally decontaminated and removed.

A small percentage of bats are also infected with rabies, but may not show symptoms. Rabies can be transmitted when saliva or even the body tissue of an infected animal comes into contact with another animal or human. Therefore, it is important to seek medical attention if you’ve had any unprotected, physical contact with a bat.

In addition, if an infestation develops, it is important to treat the area for bat mites and bat bugs, which will bite humans.