Pests

The tea growing environment in the North East India is conducive to a large number of pests and diseases. Detail studies have been made at Tocklai on the biology and control of tea pests during the last decades. Adequate and timely measures are to be takento reduce crop loss due to pests and diseases. Pesticides invariably leave residues and their indiscriminate use may render the teas unsuitable for consumption and trade. With ever growing concern over pesticide residues and the rising costs of the pesticides, the concept of pest control has undergone radical changes. Therefore, monitoring of pests for their early detection, integrated management of pests (IPM) and discretion on the choice of pesticides to be used on tea is of utmost importance.

 

 

The major pests, their site of attack on the tea plant, the period of occurrence in North East India, their mode of dispersal and some of the alternate hosts are shown in the following table.

 Major tea pests, site of attack and time of occurrence

Pests Site of attack / nature of damage Life stages / time of
occurrence
A) Chewing pests
Bunch caterpillar
(Andraca bipunctata)
Young larva : young leaf,
epidermis removed
Moths Mar-Apr/May-Jun/Jul- Aug/Oct-Nov
Caterpillar Mar-Apr/May-Jun/ Jul – Aug/Oct- Nov
Mature larva : entire leaf eaten away. Defoliation Pupa Apr-May/Jun-Jul/Aug-
Sep/Oct-Nov
Looper caterpillar
(Buzura suppresseria)
Young larva : Small holes on margins of young leaf Moths Feb-Mar/May/ Jul/Aug-Oct
Caterpillar Mar-Apr/May-Jun/Jul -Aug – Sep- Oct
Mature larva : Whole leaf eaten away. Defoliation Pupa Apr-May/Jul-Aug-Sep/Oct- Nov
Red slug caterpillar(Eterusia magnifica) Under surface of mature leaf, bark of young stem eaten away. Defoliation Moth Feb-Mar/May/ Jul/Aug-Oct
Caterpillar Mar-Apr/May- Jun/Jul- Aug
/Sep-Oct
Flush worm (Lespeyrasia leucostoma) Pluckable shoots /
leaves tied up in nest
formation
Caterpillar
Moth
Jan – May
B) Sucking Pests
Helopeltis
(Helopeltis theivora)
Young leaves/buds/tender

stems; Develop light to dark brown transluscent
irregular sucking spots/shoot growth retarded

Adult
NymphsEgg
Feb-Nov
Jassid
(Empoasca flavescence)
Young leaves/tender stems;
Develop dark browndiscoloration of leaf margin
(Rim blight)/leaf curve inward
mid rib and veins turn brownish/Shoot growth retarded.
Adult
Nymphs
Egg
Feb-Jul
Thrips
(Scirtothrips dorsalis)
Unopened or partly opened buds/young succulent leaves; Adult
Nymphs
Egg
Jan-Jul
Aphids
(Toxoptera aurantil)
Buds/tender stems/young

leaves

Adult/nymph Jan-Apr
C. Mite Pests
Red spider mite
(Oligonychus coffeae)
Upper surface of young/
mature leaves. Brownish
discoloration/defoliation.
Whole year
Scarlet mite
(Brevipalpus phoenicis)
Under surface of leaf.
Brownish discolorationalong the mid rib/veins/petiole of leaf/splits on

bark / defoliation of

young tea.

Feb-Nov
Pink and Purple mite
(Acaphylla theae and
Calacarus carinatus)
Upper surface of leaf.
Pinkish/ copperishdiscoloration on
leaf/veins
Feb-Nov


Mode of dispersal of some major tea pests

Mode of dispersal
Red spider mite Wind, Pluckers, Cattles, Weed host
Scarlet mite Weed host
Bunch caterpillar Bush to bush migration of caterpillar, Migration of moths
Looper caterpillar Migration from shade trees, Migration of moths
Red slug caterpillar Migration of caterpillar through ground, Migration of moths
Nettle grub Bush to bush migration of caterpillar, Migration of moths
Flush worm Shoot to shoot migration of caterpillar, Migration of moths
Thrips Migration of adults
Helopeltis Migration of adults

Important weed hosts of tea pests in North East India

Weed hosts Pests
Ageratum conizoides Root knot nematode
Borreria hispida Root knot nematode and scarlet mite
Commelina bengalensis Root knot nematode and scarlet mite
Clerodendron infortunatum Scarlet mite
Malastoma malabethricum Helopeltis, Scarlet mite and Red spider mite
Mikania micrantha Helopeltis
Pouzolzia indica Root knot nematode and scarlet mite
Urena lohata Red spider mite
Oxalis corymbosa Root knot nematode
O. acetocella Helopeltis

Cultural operations :

    1. Bush sanitation/Cold weather practices
    2. Ground sanitation
    3. Balanced nutrition
    4. Soil rehabilitation prior to replanting.
    5. Improved drainage
    6. Proper shade management
    7. Soil amelioration

Mechanical and Physical Methods :

    1. Hand collection
    2. Light trapping

 

Pests Life stages Mechanical / cultural control methods
Bunch caterpillar Moths
Caterpillar
Light trapping/Hand collection
Pupa Hand collection (from soil around tea

bush/shade tree)

Looper caterpillar MothsCaterpillar Hand collection (from shade tree)
Pupa Hand collection (from tea/around collar)
Red slug caterpillar Moth Hand collection/Light trapping
Caterpillar Used engine oil barrier on ground
Pupa Hand collection (from stems/forks/dryfallen leaves)
Helopeltis Adult Hand collection in morning and evening.
Nymphs
Egg Hand plucking and removal of infested shoots.
Cockchafer Adult Hand collection
Thrips Pupa & Soil stirring /caustic washing
Nymphs Removing lichens & mosses
Egg Hard plucking
Aphids Adult &
Nymph
Removal of infested shoots
Tea seed bugs Adult &
Nymphs
Hand collection
Termites Queens and
workers/nest
Digging out/killing/ destruction by using
insecticides

 

Regulatory Methods :

Only healthy, pest and disease free planting materials should be procured/used.

Biological methods :

BiocontrolBiological methods of control involve the conservation, preservation and introduction of natural enemies of tea pests, like predators, parasitoids and pathogens for suppression of pests within tolerable levels. More than one hundred indigenous natural enemies (predators, parasitoids and pathogens) have been recorded against various tea pests. A list the identified natural enemies against their respective hosts aregiven in the table below:

 

Some common indigenous natural enemies of major tea pests

Tea pests Natural enemies
Red spider mite Stethorus gilvifrons, Agistemus hystrix
Chrysoperla carnea
(P)
Scarlet, Pink & Purple mite Agistemus hystrix (P)
Bunch caterpillar Cantheconidia furcillata, (P), Dipterus fly (Ps)
Looper caterpillar Apanteles sp. (Ps), Bacillus thuringiensis (Pth)
Red slug caterpillar C. furcillata (P), Apanteles sp. (Ps)
Nettle grub C. fucillata (P)
Flush worm Apanteles sp. (Ps)
Aphid Leis dimidiata, Menocillus sexmaculatusw, Verania vincta, Syrphid (P)
Helopeltis C. carnea, Oxyopes sp. (P), Mermethid worms
(Ps)

(P : Predator, Ps : Parasitoid, Pth : Pathogen)

 

adult predatory miteadult predator S_gilvifrontsPesticide can have detrimental effects on natural enemies thereby disturbing the bio-diversity and the balance in natural ecosystem. It is therefore necessary that the indigenous predators, parasitoids and pathogens are adequately preserved. Less toxic, selective pesticides should be preferred as much as possible, to keep the natural enemies active in tea areas.            

Chemical control & Choice of Pesticides

Different groups of synthetic organic insecticides have been recommended against major and minor pests in tea after regular bioassay tests and multilocation field screenings for efficacy and residues. The maximum permissible residue limits for pesticides in tea fixed by different international regulatory bodies have restricted the choice of pesticides.

The details of the recommended pesticides are given in QUARTERLY ADVISORY BULLETINS

TRA has organized awareness campaigns among the tea planters of this region through seminars and conferences highlighting the need for safer plant protection schedules for minimizing residues so that tea continues to be a health drink. TRA has also generated data on residues of commonly used pesticides in tea through extensive supervised field trials. A number of invoice tea samples have also been monitored for pesticide residues recently, which reveals that most of the samples have residues well below the MRL limits.

Steps to minimize pesticide residues in tea

  • Monitoring and early detection of pests
  • Integrated pest management
  • Use of safer pesticides, botanicals and bioagents
  • Avoid repeated spraying of the same pesticide
  • Allow sufficient waiting period between spraying of pesticides and plucking
  • Spot treatment

Pesticides approved for use in flushing and non-flushing seasons

Season Pesticides


Mode of action
Flushing/ Plucking Season Endosulfan Contact and stomach
(Mid  February to November) Dicofol Contact
Sulphur Protective
Alphamethrin Contact and stomach
Neem formulations Disrupt insect moulting/growth
(Azadirachtin) antifeedant action
Etofenprox Contact and stomach
Cartap hydrochloride Systemic with contact and stomach
Non- flushing season Thiometon Systemic with contact and stomach
(December to Mid February) *Acephate Systemic with contact and stomach
Dimethoate Systemic with contact and  stomach
Fenitrothion Contact and stomach
Fenvalerate Contact and stomach
Fluvalinate Contact and stomach
*Chlorpyriphos Contact and stomach and vapour
Cypermethrin Systemic with contact and stomach
*Quinalphos Contact and stomach
Formothion Contact and stomach