The document summarizes the current status and potential of biological control for insect pests and diseases affecting citrus. It outlines that citrus faces numerous pests and diseases that are currently controlled through pesticides, but that biological control provides an environmentally friendly alternative. The document then reviews several major citrus pests and diseases, their impacts, and examples of existing or potential biological control agents being used against each one. It concludes that biological control alone or as part of integrated pest management is an effective non-chemical strategy for controlling citrus pests.

1. Currentstatusandpotentialof biologicalcontrol
of insectpest anddiseaseof citrus
AGRICULTURE AND FORESTRY UNIVERSITY
FACULTY OF AGRICULTURE
RAMPUR, CHITWAN, NEPAL
Presenter: Manish Kumar Pal
ENT-03M-2018
12th Magh ,2075

2.  Term “Biological control" was first used in 1919 by
“Harry Scott Smith” in meeting of American
AssociationofEconomicEntomologists, California.
Biological control is the natural ecological
phenomenon of population regulation that results
from the interaction of the biotic components of
the environment (Yazdani and Agarwal, 1997).
Rachel Carson stated biological control as the
main way ‘nature’ prevents over population by
insects in her book ‘Silent Spring’ (van Emden &
Peakall, 1996).
 Simply, Eradication or supression of undesirable
pests by encouragement, artificial introduction and
increase their natural enemies such as predators,
parasites and disease causing organisms is called
biological control.
12th Magh, 2075

3. Citrus ecosystem, offers ideal conditions for
the proliferation of numerous pests and
diseases.
The continuous use of pesticides has resulted
in resistant pest populations, leading to pest
control failures with severe economic
consequences (Pimentel 2005).
Pesticide residues are found principally in the
peel of citrus fruits
Citrus producers, processors and end users, are
driving the demand for chemical-free products.
To meet this demand, non-chemical pest
control strategies are required, needing to be
both efficient and environmentally friendly as
well as guarantee similar production yields
Biological pest control represents such an
alternative to chemical pesticides.
12th Magh, 2075

4. Common pests of citrus with their
Biological control
California Red Scale ( Aonidiella aurantii )
It’s main damage is cosmetic, related to the presence
of scales on fruits.
Periodic releases of the parasitoid aphytis melinus
(100,000/ha/year), managed to maintain the pest
populations below economic damage limits (Moreno
and luck, 1992).
Citrus psyllid ( Diaphorina citri )
Suck sap from the plants and injection of toxic saliva.
Excrete honeydew which results growth of sooty
moulds
It also transmits the "greening" in citrus.
Attacked by many natural enemies, including lady
beetles, lacewing larvae, syrphid larvae, minute pirate
bugs, parasitic wasps, spiders, and birds.
Most promising biological control agents is the
parasitoid wasp, Tamarixia radiata
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5. Cottony cushion scale: Icerya purchasi
Nymphs and adults suck the sap from leaves
The most famous one is the vedalia beetle, Rodolia
cardinalis.
Other important natural enemy, the parasitic
fly Cryptochaetum iceryae, deposits one to four eggs
inside each second-instar, third-instar, or adult female
scale body.
Mealy bug: Planococcus citris
Suck the sap from the cells of tender branches and fruits
turn pale colour.
Large amounts of honey dew excrete
Chemical control of the citrus mealy bug is difficult.
(Dean et al., 1971)
Field release of australian lady bird beetle, cryptoleamus
montrouizeri 10 per tree found to be effective
The parasitic wasp, Anagyrus pseudococci, parasitizes
citrus mealybug larvae. The parastitized pupa swells
becoming a hard yellow brown mummy.
12th Magh, 2075

6. Citrus/lime/lemon butterfly: Papilio demolious
Caterpillars prefers on light green tender leaves
feeding voraciously and leaving only the mid-ribs.
The young caterpillars of PDL were attacked by the
yellow wasp (Polistes hebreus F.), preying mantis
(Creobrator gemmatus) and spiders.
Apanteles lunatus and Pteromalus puparum are
natural enemies of larvae and pupae on Papilio
demoleus as observed in citrus orchards of Nepal.
Black aphid: Toxoptera aurantii / Brown
aphid: Toxoptera citricida
Feed on tender foliage and flowers and transmit
tristeza virus disease.
Aphid parasites include the wasp
genera Aphidius and Aphelinus:
Aphids are attacked by many generalist predators
include hoverfly larvae (syrphids), ladybird beetles
and lacewing larvae
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7. Common Diseases of citrus with their
Biological control
Powdery Mildew : Oidium tingitanimum
All the aerial parts of the plant are
attacked. This disease is characterized by a
whitish, mealy powdery growth on young
leaves and twigs, which covers the entire
leaf and young growing shoots
Applications of Bacillus subtilis on post-
bloom fruit drop of citrus.
Citrus Gummosis -Phytophthora spp.
The symptoms appear as yellowing of
leaves, followed by cracking of bark and
profuse gumming on the surface.
Gade (2012) reported that, in vitro
antagonism showed by Trichoderma
harzianum and T. virens (84.96%) suppress
P. parasitica significantly.
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8. Citrus canker- Xanthomonas axonopodis pv. Citri
Young lesions are raised on both surfaces of the leaf,
but particularly on the lower leaf surface.
Bacillus subtilis (S-12) to citrus canker bacterium on
single application is highly encouraging and deserves to
be tried as a new recommendation for controlling citrus
canker.
Biological control of citrus canker using actinomycetes
(Takeuchi et al., 1988) and fungal inhibitors (Masroor
and Chandra, 1989) has also been attempted.
Citrus Greening :Candidatus Liberibacter asiaticus
The fruits of affected trees remain mostly green even on
maturity and the fruits, which are directly exposed to
sun show a conspicuous yellow patch on the rind
surface.
Also known as HLB, which refers to its original name
in Chinese (Huanglongbing, or yellow dragon disease).
For biological control , raise the wasp species Tamarixia
radiata—a natural enemy of the psyllid on murraya
peniculata or infested citrus plant.
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9. Conclusion:
Citrus are damaged by a broad range of pests and diseases and
chemical phytosanitary products are commonly applied in
order to protect the crop
Pesticides may enter the food chains, accumulate and harm
other organisms.
Biological pest control, alone or as a part of an Integrated Pest
Management (IPM) strategy, represents such an alternative to
chemical pesticides.
 This is a method of pest control that uses other organisms that
are predators or parasites of the pest to reduce pest numbers to
low levels at which there is little economic damage to citrus.
12th Magh, 2075

10. References:
Dean, H.A., W.G. Hart and S.J. Ingle, 1971. Citrus mealybug, a
potential problem on Texas grapefruit. J. Rio Grande Val. Hortic.
Soc., 15: 46-53
Gade, R. M. (2012). Biological and chemical management of
Phytophthora root rot /collar rot in citrus nursery. The Bioscan
7(4): 631-635.
Masroor, M.K. and Chandra, S. 1989. Effect of carbon sources
on antibiotic production by Aspergillus sp. antagonistic to citrus
canker pathogen. Philippines Journal of Science, 118(2):141-145.
Takeuchi, T., Hara, T., Naganawa, H., Okada, M., Hamada, M.,
Umezawa, H., Gomi, S, Sezaki, M. and Kondo, S. 1988. New
antifungal antibiotics, benanomicines A and B from an
actinomycetes. Journal of Antibiotics, 41(6): 807-811.
12th Magh, 2075

11. Acknowledgement
Respected Teacher Dr. Resham B. Thapa
PHD (Retired), Professor Of Entomology
Friends of Entomology Departments
Friends of all departments