Biological insecticides derived from bacteria like Bacillus thuringiensis (Bt) and Bacillus sphaericus are effective at controlling insect pests with low toxicity to humans and the environment. Bt produces crystal proteins that are toxic only to the larvae of target insects when eaten. Varieties like Bt kurstaki control lepidopteran pests, Bt israelensis controls mosquitoes and blackflies, and genetically engineered crops produce Bt toxins. Bacillus sphaericus controls mosquito larvae through a binary toxin. These biological insecticides are useful alternatives to chemical pesticides in integrated pest management programs.

1. Usage spots of biological insecticides in consort with target insect pests or vectors and application in habitat
IJEN
Usage spots of biological insecticides in consort with
target insect pests or vectors and application in habitat
Muhammad Sarwar*
*Department of Entomology, Nuclear Institute for Food & Agriculture (NIFA), Tarnab, Peshawar, Pakistan,
Corresponding author: E-mail: drmsarwar64@yahoo.com
The greatest risks to our environment and health come from chemical insecticides, therefore,
overall objective of this article is to protect health of consumer and ensure fair practices in
insect and vector controls. Biological insecticides are living organisms or toxins produced by
bacteria, viruses and fungi having low toxicity to humans and non-target insects. Bacterium
Bacillus thuringiensis and Baculo virus infect an insect when it ingests them. Others
microorganisms, such as fungi, Beauveria bassiana, deposit themselves on insect’s carapace
and infiltrate organism that is fatal to ravaging pests. The B. thuringiensis is an insecticidal
bacterium, marketed worldwide for control of many important plant pests, mainly caterpillars of
Lepidoptera (butterflies and moths), but also mosquitoes and simuliid blackflies vectors.
Commercial Bt products are powders containing mixture of dried spores and toxin crystals used
on crops and ornamental plants, around buildings, in aquatic settings, and in aerial applications
that are commonly sprays, dusts, granules and pellets. Some crops have been engineered to
make the Bt toxin and these plant-incorporated protectants include corn, cotton, and soybeans.
Baculo viruses are widely used both as protein expression in vectors and as insect pest control
agents, and progress has been made in genetic enhancement of baculo viruses for improved
insecticidal efficacy. Treating of crops and stagnant water or pools with Bt can definitely
decrease the number of pests and vectors larvae, and therefore, number of adults, but growers
and householders may still need to use traps, repellants or other control methods to prevent all
pests in an area.
Key words: Biological Insecticide, Entomopathogen, Bacillus, Larvicide, Baculo virus
INTRODUCTION
While using of chemical insecticides, humans quickly
realized that it would be necessary for them to use other
means to protect the environment. The use of microbes
pathogenic only to insects nowadays allows for biological
control, which restricts the damage caused by
devastating insects without harming other organisms.
Thus, the liabilities of chemical insecticides have
encouraged interest in biological control tactics, which
turn natural processes and mechanisms against pest
insects and have only few harmful side effects of
environment (Bah et al., 2004; Stalinski et al., 2014).
Today, biological insecticides with microorganism-based
insecticidal action are part of crop protection practices
worldwide. They give to farmers a new effective option,
allowing them to vary their pest control measures and
prevent the potential development of resistance. These
products comply with the tenets of integrated pest
management and they can be applied multiple times and
even shortly before the harvest. As such, biologicals
insecticides are an important tool in sustainable
agriculture. Growers need day-to-day management tools
which can make farming more successful and
convenient. Efficient control of devastating sucking pests
makes crop management easy and leads to superior
International Journal of Entomology and Nematology
Vol. 3(1), pp. 014-020, June, 2016. © www.premierpublishers.org. ISSN: 2326-7262
Review

2. Usage spots of biological insecticides in consort with target insect pests or vectors and application in habitat
Sarwar M 014
profitability of produce. In practice, however, some of the
environmentally attractive features of biological
insecticides such as their inherently slow and selective
activity, and strict management requirements can make
them economically unattractive to farmers(Sarwar, 2015
a; 2015 b; Sarwar and Salman, 2015 a). Increasingly,
therefore, biological and chemical methods can be
coordinated in Integrated Pest Management (IPM)
programs.
Bacillus thuringiensis
The Bacillus thuringiensis (commonly known as Bt) is a
gram-positive, soil-dwelling bacterium, commonly used
as a biological pesticide. B. thuringiensis also occurs
naturally in the gut of caterpillars of various types of
moths and butterflies, as well on leaf surfaces, aquatic
environments, animal feces, insect-rich environments,
and flour mills and grain-storage facilities. During
sporulation, many Bt strains produce crystal proteins
(proteinaceous inclusions), called δ-endotoxins, that have
insecticidal action. When B. thuringiensis is viewed by
phase contrast microscopy, the vegetative cells contain
endospores (phase bright) and crystals of an insecticidal
protein toxin (delta endotoxin). Most cells have lysed and
released the spores and toxin crystals (the structures with
a bipyramidal shape).This has led to their use as
insecticides and more recently to genetically modified
crops using Bt genes. However, many crystal-producing
Bt strains, though do not have insecticidal properties, but
Bt makes toxins that target insect larvae when eaten and
in their gut the toxins are activated. The activated toxin
breaks down their gut, and the insects die of infection and
starvation. The different types of Bt create toxins that can
only be activated by the target insect larvae. In contrast,
when people eat the same toxins, the toxins are not
activated and no harm occurs (Xu et al., 2006; Knowles,
1994).
For many years, Bt is available only for control of
lepidopteran insects, using a highly potent strain (B.
thuringiensis var. kurstaki) and this strain still forms the
basis of many Bt formulations. Further screening of a
large number of other Bt strains revealed some others
that are active against larvae of coleopteran (beetles) or
dipteran (small flies, mosquitoes). Most of these strains
have the same basic toxin structure, but differ in insect
host range, perhaps because of different degrees of
binding affinity to the toxin receptors in the insect gut. For
example, the toxins produced by B. thuringiensis var.
aizawai have somewhat different toxins from those of B.t.
var. kurstaki and they are highly specific to Lepidoptera,
with no effect on other insects. In contrast, the toxins
produced by strains of B.t. var. israelensis are highly
active against simuliid blackfly vectors of some tropical
diseases, and also against fungus gnat larvae and some
types of mosquito (especially Aedes species, but higher
toxin doses are needed for control of Culex spp., and
Anopheles spp.). Strains of B.t. var. sandiego or B.t. var.
tenebrionis are marketed for control of some
coleopterans, especially for control of the important pest
Colorado potato beetle (Roh et al., 2007; Nicolette, 2009;
Sarwar, 2014 a; 2014 b).
Each type of Bt toxin is highly specific to the target insect,
for example, the ‘kurstaki’ type targets caterpillars, and
‘isrealensis’ targets immature flies and mosquitoes. In the
course of sporulation, Bacillus sphaericus produces an
inclusion body which is toxic to neither a variety of
mosquito larvae, and not causing mammalian toxicity nor
apparent perturbation of the environment. The
commercial Bt products are powders containing a mixture
of dried spores and toxin crystals. They are applied to
leaves or other environments where the insect larvae
feed. The Bt products are used on crops and ornamental
plants, around buildings, in aquatic settings, and in aerial
applications. Some of these products are approved for
use in organic agriculture those are commonly sprays,
dusts, granules and pellets (Ibrahim, 2010).
Plants Genetically Engineered with the Bt Gene
A wide range of crop plants have been genetically
engineered to contain the delta-endotoxin gene from B.
thuringiensis. These Bt crops are now available
commercially and they include Bt corn, Bt potato, Bt
cotton and Bt soybean. Such plants have been
genetically engineered to express part of the active Cry
toxin in their tissues, so they can kill insects that feed on
the crops. In some aspects, this is an important
technological and practical development, because it
ensures that only those insects that attack the crop can
be exposed to Bt toxins and there is no risk to other types
of insect. It also ensures that the range of uses for Bt is
extended to insects that feed on the roots or that bore
into the plant tissues, for example, the European corn
borer because such insects cannot be controlled by Bt
suspensions sprayed onto plant surfaces. However, there
is also a downside, because the target insects are
perpetually exposed to toxins and this creates a very
strong selection pressure for the development of
resistance to the toxins. So, various crop management
strategies are being developed to try to minimize this risk
(Madigan and Martinko, 2005; Sarwar, 2015 c).
The are several dozen recognized subspecies of B.
thuringiensis, but subspecies commonly used as
insecticides include Bacillus thuringiensis subspecies
kurstaki (Btk) and subspecies israelensis (Bti) and
subspecies aizawa (Bta).
Bacillus sphaericus
Bacillus sphaericus is a rod-shaped, strictly aerobic, gram
positive bacterium which is used as an insecticide against
certain strains of disease-carrying (or just annoying)

3. Usage spots of biological insecticides in consort with target insect pests or vectors and application in habitat
Int J. Entomol. Nematol. 015
mosquitoes. B. sphaericus is an obligate aerobe
bacterium with rod shaped cells that form chains, used as
a larvicide for mosquito control. The bacteria, when
ingested by a mosquito larva, secrete a binary toxin
which causes the larvae to stop feeding and therefore
starve. It has no known effect on mature adult
mosquitoes or their pupae. The larvicide of B. sphaericus
is unique in that it consists of two proteins of 51 and 42
kDa, both of which are required for toxicity to mosquito
larvae. There is a low level of sequence similarity
between these two proteins, which differ in their
sequences from all the other known insecticidal proteins
of B. thuringiensis. Within the midgut the 51- and 42-kDa
proteins are processed to proteins of 43 and 39 kDa,
respectively. The conversion of the 42-kDa protein to a
39-kDa protein results in a major increase in toxicity and
the significance of the processing of the 51-kDa protein is
not known. In contrast to the results with mosquito larvae,
the 39-kDa protein is alone toxic for mosquito-derived
tissue culture-grown cells and this toxicity is not affected
by the 51-kDa protein or its derivative, the 43-kDa protein
(Baumann et al., 1991).
Comparisons of larvae from species which differ in their
susceptibility to the B. sphaericus toxin indicate that the
probable difference resides in the nature of the target
sites of the epithelial midgut cells and not in uptake or
processing of the toxin. A similar conclusion is derived
from experiments involving tissue culture-grown cells
from mosquito species which differ in their susceptibility
to the B. sphaericus toxin. For developing an active tablet
formulation for use in urban mosquito breeding sites, it is
performed in three phases, analysis and standardization
of a B. sphaericus fermented culture; physical, chemical
and biological analysis of the active powder (solubility,
residual humidity, particle size, resting angle, flowing off
time, compacted density and biological activity against
Culex quinquefasciatus larvae; and the development of
fast-disintegrating tablets. Five formulations with differing
compositions have been developed and the active
powder caused 100% larval mortality from 1 day to 2
months after a single treatment under simulated field
conditions. Control has been seen particularly against
Culex, Anopheles and Psorophora species, with
somewhat less control against Aedes species. It is
applied by hand-held application equipment to water
bodies and rates of application depend upon the stage of
larvae to be treated and the organic content of the water.
Rates between 2 and 4 kg of product per hectare are
recommended, with the highest rates used against large
larvae and in highly polluted water (Clark and Baumann,
1991; Poopathi and Abidha, 2010).
Bacillus thuringiensis aizawi
Bacillus thuringiensis aizawai strain is a part of a large
group of bacteria that occur naturally in soil. B.t. aizawai
strain is known to be toxic to numerous species of moths,
including many pests of agricultural crops. So, their uses
are agricultural crops or other use sites where moth
larvae are pests. It can be applied by several spray
methods including hand spraying, aerial applications,
ground based applications and through irrigation
systems. B.t. aizawai strain is important control agents for
lepidopteran pests. Bioassays have designed to test B. t.
kurstaki and B.t. aizawai against second and fourth
instars of black cutworm Agrotis ipsilon (Hufnagel)
(Lepidoptera: Noctuidae) larvae with and without Bacillus
species. Bacteria B. thuringiensis subsp. Aizawai is more
toxic to both second and fourth-instars black cutworm,
larvae than B.t. kurstaki at 7d after treatment (DAT). No
harmful health effects to humans are expected from use
of B.t. aizawa strain as a pesticide active ingredient. No
evidence of toxicity or infectivity is found in animal
laboratory studies. Furthermore, the use of this bacterium
in pesticide products will not increase the exposure of
humans beyond normal background levels. Laboratory
studies showed no evidence indicating that B.t. aizawai
strain is harmful to non-target insects, birds, mammals,
plants, or marine species. In addition, exposure to wildlife
is not expected to increase above background levels from
pesticidal use of this bacterium (Asano et al., 2000;
Tamer et al., 2011).
Bacillus thuringiensis israelensis
The discovery of B. thuringiensis israelensis (Bti), a
variety specific to Diptera (especially mosquitoes and
blackflies), has led to the development of many products
based on this bacterium. These products have been used
extensively in mosquito and biting fly control programs.
The mode of action of Bti involves the synergistic
interaction of four toxic proteins. Bti rarely recycles in
natural environments and the insect’s toxicity is due to
crystal proteins formed during sporulation. The Bti is
relatively specific to the Nematocera suborder of Diptera,
in particular filter-feeding mosquitoes (Culicidae) and
blackflies (Simuliidae). It has also been shown to be
pathogenic to some species of midges (Chironomidae)
and Tipulidae, although usually to a lesser extent than
mosquitoes and biting flies. Bti has not been reported to
affect a large number of other invertebrate species
including most aquatic fauna. It is not toxic to bees and
fish are not affected, either in the laboratory or after field
application. Bti is considered to pose little threat to
mammalian safety and its inoculations to animals and
humans have not resulted in clinical symptoms. Concerns
have been raised that the solubilized δ-endotoxin of Bti
activated in the laboratory is toxic to mice when
administered by injection and cytolytic to human
erythrocytes. However, solubilization occurs at high pH
(such as in insect guts) and does not occur in mammalian
guts. Generally, reports of activity after application show
a decline in efficacy within days and little residual activity

4. Usage spots of biological insecticides in consort with target insect pests or vectors and application in habitat
Sarwar M 016
after several weeks. Bti does not persist in the
environment after application and after application is
dependent on the type of formulation/product used, with
some formulations (pellets/briquettes) designed
specifically to enhance residual activity. Some insects,
especially Lepidopterans, have become resistant
following constant application of Bt strains. However,
resistance has not occurred after application of Bti,
possibly due to the complex mode of action, involving
synergistic interaction between up to four proteins. Use of
a single protein from Bti for mosquito control resulted in
resistance after only a few generations in the laboratory
(Glare and O'Callaghan, 1998).
Bacillus thuringiensis kurstaki
The kurstaki strain controls the larva stage (caterpillars)
of certain moths and butterflies such as tomato and
tobacco hornworm, cabbage worms, loopers, leaf rollers,
bagworms, gypsy moths, tent caterpillar, fall webworm
and others. Ingestion of the bacterium paralyzes the
digestive system of the insect and it stops feeding within
hours. Btk affected insects usually die within several days
of ingesting the bacteria. Since Btk is most effective on
young, heavily feeding insect larvae populations must be
monitored to insure that the targeted insect is in the
proper stage for optimum control. Btk may be applied up
to the day of harvest on a variety of food crops. This
biological insecticide is available as a dust or in a liquid
concentrate form. There are many advantages to using
Btk to control caterpillar pests. That is, the caterpillars
that become ill or die after ingesting Btk are not
considered dangerous to birds or other animals that feed
on them. In general, sunlight and other microbes destroy
Btk applied to foliage within three to five days, it does not
multiply or accumulate in the environment. Perhaps most
importantly, Btk does not appear to pose any significant
threat to human health or to pets. Btk is often sprayed
over large areas from planes or helicopters in formal
gypsy moth control programs over large areas, but
commercial applicators or homeowners can apply it
effectively to individual trees from the ground. When Btk
is ingested by a susceptible caterpillar, the highly alkaline
environment of the caterpillar’s gut triggers its bacterium
to release a crystalline protein called an ‘endotoxin’ that
poisons the insect’s digestive system. The endotoxin acts
by killing cells and dissolving holes in the lining of the
insect’s gut. When a mixture of food, Btk spores and
digestive juices leak through these holes into the insect’s
blood, it causes a general infection that kills the
caterpillar (Van Netten et al., 2000; Siegel, 2001).
The Btk in its various formulations can be applied using
both ground and aerial spray methods. Aerial spraying
may be used in forestry and urban areas to ensure
adequate coverage and effectiveness. Btk has been used
on millions of acres of wooded areas and agricultural
crops in many countries worldwide. Btk products are
used to control gypsy moth, spruce budworm and other
specific pests in forestry and urban settings, as well as
certain insects that feed on vegetable and fruit crops.
Timing of Btk applications is critical to successful control
of caterpillars. Because it is a stomach poison, and since
gypsy moths only feed when they are in the caterpillar
stage, it is important that Btk should be sprayed on
leaves of trees when caterpillars are actively feeding. It
has little effect on the gypsy moths non-feeding life
stages (eggs, pupa and adult stages) and is most
effective against young, actively feeding caterpillars.
Make two applications of the spray over the course of
2weeks to ensure that susceptible caterpillars are
treated. Apply the first spray on the tree foliage about 10
days after caterpillars have hatched from their eggs, and
apply again 2 weeks later while caterpillars are still in
active stage. Do not apply the first spray until all
caterpillars in the area have hatched, apply late in the
day to avoid intense sunshine to avoid its breaks down,
apply when winds are relatively calm to avoid spray
drifting and obey all safety precautions. As with any
pesticide, be sure to follow all safety precautions and
wear personal protective equipment (goggles, gloves,
hat, long pants and long-sleeved shirt)as specified on the
label (Tayabali and Seligy, 2000).
Bacillus thuringiensis tenebrionis
Bacillus thuringiensis (Bt) toxins present a potential for
control of pest mites. The toxic effect of Bacillus
thuringiensis var. tenebrionis producing Cry3A toxin has
been tested on the mites Acarussiro L., Tyrophagus
putrescentiae (Schrank), Dermatophagoides farinae
Hughes, and Lepidoglyphus destructor (Schrank) via
feeding tests. After 21 days, the mites have been counted
and var. tenebrionis Bt diet suppressed population growth
of the four mite species with no remarkable differences
among species. The Colorado potato beetle has
developed unprecedented resistance to multiple
applications of chemical insecticides. Bt-sd and Bt-t are
toxic to a limited range of leaf-eating beetle species and
are now considered to be the most effective control for
this destructive insect pest. It can also be used to control
the elm leaf beetle and may be used on potatoes,
eggplant, tomatoes and elms. This biological pesticide
should be applied to the young larval stages, as it has no
effect on adult beetles, and is safe for people, pets,
wildlife or fish (Erban et al., 2009).
Baculo viruses
Insect viruses (also called baculo viruses) are naturally
occurring insect specific pathogens and have been part
of the environment for millions of years. These baculo
viruses play an important role in natural control of

5. Usage spots of biological insecticides in consort with target insect pests or vectors and application in habitat
Int J. Entomol. Nematol. 017
insect populations and have no effect on other animal or
plant life. Baculo viruses are ingested by insect larvae
causing infection of the insect's cells and its death occurs
in 3 to 8 days, depending on the larval species and in
star. These organisms are known to be very slow in
killing the insect and this is one of the major issues
affecting their expansion in insect control programs.
However, the probability is high for development of
genetically engineered viruses that carry a specific toxin
to the target insect. Increases in the speed of kill of up to
60% have been reported by various researchers (Sarwar,
2015 d).
Nuclear Polyhedrosis Virus (NPV)
The nuclear polyhedrosis viruses are rod shaped,
elongated particles enclosed in protein crystalline
matrices which are occlusion bodies (OBs). Insects must
consume the OBs from the surface of the leaf to become
infected with the virus. The OBs are quickly dissolved
within the midgut of the caterpillar, releasing the
infectious virus particles. The virus penetrates the gut
and moves into the insect’s body, sealing its fate. Within
three or four days, the caterpillar becomes sluggish and
feeding slows considerably. The internal organs start to
disintegrate and caterpillars begin to die about five days
after ingestion. Shortly after death, the body ruptures,
releasing billions of new OBs that, under the right
conditions, will infect other caterpillars. Polyhedrosis virus
is a biological insecticide; hence its efficacy is dependent
on environmental conditions, application and feeding
behavior of the pest. Apply it at emergence of larvae i.e.,
small larvae up to 13 mm in length in all crops other than
cotton and up to 7 mm in length in cotton if larvae
numbers exceed 4/ m. In sorghum apply 3 days after
50% of panicles have reached 100% flowering, and for
chickpeas if larvae numbers exceed 6/m to reduce the
numbers below threshold (Bonning and Nusawardani,
2007).
The performance of polyhedrosis viruses is enhanced by
the presence of beneficial insects. For this reason, prior
to use avoid applying of insecticides which might disrupt
the beneficial populations. Polyhedrosis virus needs to be
ingested to be effective, so coverage of the target area,
where the larvae are feeding, is essential. It is readily
degraded in the presence of ultra violet light, so, it should
preferably be applied in the late afternoon or early
evening. This can ensure that larvae feeding during the
night will have a significant opportunity to ingest the
product before it is degraded. The product acts slowly
and can take up to 8 days to kill larvae, and speed of kill
and efficacy is dependent on climatic conditions wherein
warm conditions will favor the performance as the larvae
will be feeding actively and moving around. Daytime
temperatures of 25
o
C to 35
o
C are ideal. Apply in sufficient
water and using application parameters (nozzles, swath
width, pressure, boom height and speed) to ensure
thorough coverage of the target area (Cory et al., 2003).
Cydia pomonella granulovirus
The Cydia pomonella granulosis virus is a granulovirus
belonging to the family Baculoviridae and it has a double-
stranded DNA genome. The virus forms small bodies
called granules containing a single virion. The C.
pomonella or codling moths are proved to be a
problematic pest on several fruit trees, including apples
and pears. The caterpillars burrow into the fruit, rendering
it un-sellable or consumption. Traditional insecticides are
of limited use, as some strains have acquired resistance
to several insecticides. Granulosis is a virus of
invertebrates specifically C. pomonella or the codling
moth. Granulosis virus is highly pathogenic, it is known
as a fast agent which is one that can kill its host in the
same instar as infection; thus, it is frequently used as a
biological insecticide. However, resistance of codling
moth against C. pomonella granulovirus products has
alarmed to growers, extension services, producers and
the scientific community. This contribution can provide an
overview about the different developments and the
progress made towards an improvement of granulosis
virus application in the future. Though the new findings
and developments report are very promising and give
legitimate reason for optimism, more research and new
developments are essential to not lose this long-term
battle (Jehle et al., 2006).
Entomopathogens Lecanicillium lecanii and
Beauveria bassiana
The effects of endophytic entomopathogens and their
capacity to colonize crop plants are becoming widely
recognized. Their presence in crop plants indicates the
possibility of a much greater potential for contact between
insect and fungus than previously recognized. The strains
of fungi Lecanicillium lecanii and Beauveria bassiana are
important entomopathogens of Aphis gossypii. Contact
with conidia of both fungi significantly reduced the rate
and period of reproduction of A. gossypii. The culture
filtrates of L. lecanii and B. bassiana significantly
increased mortality and feeding-choice experiments
indicate that insects may be able to detect metabolites of
the fungi. The culture filtrate of L. lecanii also significantly
reduced the reproduction of the aphid. The ethyl acetate
and methanolic fractions of the culture filtrate and of
mycelia of L. lecanii also caused significant mortality and
reduced fecundity of A. gossypii. The methanolic
fractions of mycelia of B. bassiana caused significant
mortality of A. gossypii. The present investigations
indicated that A. gossypii is affected by contact with both
conidia and fungal metabolites. This broad influence
indicates that these fungi may have a role in regulating
insect pest populations (Gurulingappa et al., 2011).
Integrated Pest or Vector Management
Integrated pest management (IPM) program focuses on

6. Usage spots of biological insecticides in consort with target insect pests or vectors and application in habitat
Sarwar M 018
the management of insect pests by manipulating predator
populations and the use of strategically applied
insecticides. With their very narrow spectrum, baculo
viruses are safe to beneficial insects or entomopathogens
has a good fit in IPM programs. Growers or householders
may want to use Bt along with other control methods,
depending on specific circumstances. It kills larvae, but is
usually not enough to get rid of all the adult mosquitoes
or caterpillars in an area. Since they grow quickly, in a
week or less, some may manage to go through the larval
stage before or after the Bt is applied. Also, even Bt
would not necessarily eliminate every larva, especially if
their breeding area is a large or inaccessible to treatment,
such as tiny scattered patches, puddles and trash or tree
holes. It is also less effective at eradicating mosquito
larvae in water with a lot of organic matter or pollution,
such as swamps and brackish ditches or cesspools. Then
there is the problem of mosquitoes from elsewhere and
adults of some species may fly for miles looking for
blood, even if experts could eliminate all the ones that
hatched nearby. Bt would kill mosquito larvae like these
without harming humans, birds, pets or fish, but the ones
that have already become pupae (the comma-shaped
ones) will still live to become adults. Treating of stagnant
water or pools with Bt will definitely decrease the number
of mosquito larvae and therefore the number of adults,
but experts may still need to use traps, repellants or other
control methods to prevent all the biting adults in an area
(Sarwar, 2015 e; 2015 f; 2015 g; 2015 h). Although
biological insecticides can be used in alternation with
synthetic insecticides, their best fit is where integrated
pest management principles have been adopted i.e.,
preservation of natural enemies such as predator (lady
beetles), parasite (Microplitus) and entomopathogens
(Ascovirus) (Sarwar, 2013; Sarwar, 2014 c; 2016 a; 2016
b).
Handling and Safety
People are most commonly exposed to Bt through their
diet, at very low levels. Exposure can also occur if
persons breathe it in or get it on their skin or eyes. For
example, this can occur while applying sprays or dusts
during windy conditions. People may also be exposed
after using a product if do not wash hands before eating
or smoking. People can limit their exposure and reduce
the risk by carefully following the label instructions. If any
exposures occur, be sure to follow the first aid
instructions on the product label carefully. In case of
contact of biological insecticides with eyes, flush with
plenty of water for at least 15 minutes. If contact is on
skin, wash thoroughly with soap and water. If inhaled,
remove victim to fresh air and apply respiration if
indicated. Get medical attention if irritation persists and
keep biological insecticides out of reach of children.
Several studies have found no evidence of sickness or
infection as a result of exposure, however, some
products with Bt have caused eye and skin irritation.
When eaten, Bt is confined to the gut, it does not
reproduce, and the toxin is broken down like other
proteins in the diet. If breathed in, Bt can move to the
lungs, blood, lymph and kidneys, and is then attacked by
the immune system (Sarwar and Salman, 2015 b; 2015 c;
Sarwar and Sattar, 2016).
CONCLUSION
Microorganisms are widely used in agriculture and
forestry, and they can be used as biological insecticides,
acting on insects in different ways. There are many
different biological insecticides, but, the most common
one refers mainly to the fungi, baculo viruses and Bts as
naturally occurring biological sprays. Biological
insecticides are currently sold in various market
segments; however, their market penetration is possible
due to competitive prices, reliable formulations and
efficacy comparable to standards. Advances in IPM
programs can increase the usage of biological
insecticides, especially in situations where the
performance of biological insecticides are below the
standard insecticides due to high insect’s pressure.
Advancements in genetic engineering and manufacturing
processes (fermentation, synthesis, formulation) can
strengthen the position of biological insecticides in the
marketplace. However a number of technological
breakthroughs will be needed to reach this level of
market share. The future of biological insecticides will
largely depend on the financial strength of the companies
involved in producing these products. Most agrochemical
companies are mainly working on Bts and this technology
is well established and it does not require a high
investment. Other companies are involved in virus,
fungus, and pheromone technologies. Further research
efforts are in progress to develop and optimize the in vitro
production process for biological insecticides.
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Accepted 22 April, 2016
Citation: Sarwar M (2016). Usage Spots of Biological
Insecticides in Consort with Target Insect Pests or
Vectors and Application in Habitat. International Journal
of Entomology and Nematology, 2(1): 019-026.
Copyright: © 2016 Sarwar M. This is an open-access
article distributed under the terms of the Creative
Commons Attribution License, which permits unrestricted
use, distribution, and reproduction in any medium,
provided the original author and source are cited.