Tropical nursery and plantation diseases

Tropical Nursery & Plantation

diseases: Symptoms, Agents,

Remedial measurements, IPM

Vikas Kumar [email protected]

PhD Scholar

Forest nurseries are integral part of forest regeneration since a nursery contributes to

successful forest regeneration.

In spite of the best efforts made nurseries suffer losses due to insect pest damage.

Insect pests occur in mother bed or in the transplant beds and even after out-planning

them in the field.

Such field losses starts with the improper management of pest problems in seedling in

nurseries, paving way for carrying over of life stages of pests of field.

So the pest problems do not confine only to nurseries.

Nursery managers must analyses the damage or losses caused by insects and the

costs involved in preventing such pest problems.

There is very great demand for seedlings of various tree species for different

plantation programmes.

In order to produce quality-planting materials, the nursery has to be managed properly

against pest insects, which may assume serious proportions resulting in partial or total

loss of planting material.

TYPES OF INSECT PESTS

No. Pest

Category Frequency of association

with the plant species Examples

a Persistent

pests Present throughout the year on

seedling

Myllocerus sp., and thrips on Elangi

b Regular pests Occurrence most frequently on

seedlings and have close

association with that species

Aphids and Psyllids on Albizia lebbeck and

Cirtrus butterfly Papilio on Aegle and wood

apple

c Occasional

pests Occur rather infrequently

without a close association

with the particular plant

species.

Bag worms on Acacia and Scale insect

Megapulvinaria on Neem

d Seasonal

pests Appear mostly during a

particular season of the year

Ghamar defoliator, Calopepla, Teak

defoliator Hyblaea, skelectonizer, Eutectona

and parnara on Pongamia

e Sporadic

pests Appear infrequently in the few

isolated localities

Scale insects on Albizia and larva of

Catopsilia butterfly on Cassia.

CATEGORIOZATION OF INSECT PESTS

NO PEST

CATEGORY STAGE OF INSECT TYPE OF INJURY ON PLANTS EXAMPLE

a Seed feeders Both adult and

immature stages

complete their life

cycle fully or in part

in seeds

Feed on seeds of trees either in the

field or during seed storage Tamarind seed

feeder Carryedon

serratus

b Defoliators Adults and/or

immature stages Feed on the leaves and cause

damage by loss of young and

mature leaves.

Teak defoliator,

Ailanthus defoliator

c Sap feeders Both adults and

immature stages Insects pierce the plant tissue with

the help of pointed mouth parts and

feed on the plant sap.

Scale insects,

plant bugs.

d Borers adults or immature

stages Insects bore into the stem or roots

of plants for feeding and shelter Pouch gall on

Pongamia

e Gall makers Adult phase, the

immature stages or

entire life cycle is

spent inside the galls

Sustained feeding

by the insects leads to the

development of abnormal structures

called galls

Pouch gall on

Pongamia

f Sub-

terranean

pests

Colonies of termities

or larval stages of

some insects

Insects remain underground and

feed both on roots and the above

ground plant parts of plants.

Termities,

White grubs

Hoplocerambyx spinicornis

INFESTED PLANT - Galls on midrib, petiole, young shoots - Initially green, turns pink and finally red - Deformed and branched seedlings

Shoot gall on Tectona grandis caused by Asphondylia tectonae

Marginal gall on leaf of Terminalia sp. Whole leaf rolled into a gall like structure

Nymph of Trioza hirsuta Adult of Trioza hirsuta

TYPES OF INJURY ON PLANTS BY INSECTS

NO TYPES OF INJURY DESCRIPTION EXAMPLE

1 DEFOLIATION

1. Free feeding Consume the whole leaf and minor veins, leaving large veins untouched Teak defoliator

2. Leaf mining Build tunnels inside the leaf tissue in between the upper and lower epidermis

resulting in irregular linear or round patches.

Pongamia blotch minor

3. Skeletonizing Feed on the leaf tissue leaving the veins intact leading to a skeletonized

appearance.

Teak skeletonizer

4. Shelter feeding Make shelter out of the plant parts like leaves, stem or flowers and then feed on

the plant

i. Leaf webbing Web leaves together for protection and feed on the enclosed foliage. Leaf webber in Elengi

ii. Leaf folding or

rolling

Roll an entire or part of the leaf, fasten it with silk and feed on it by remaining

inside

syzygium leaf roller

beetle

iii. Leaf tying Tie up leaves, debris or needles to prepare a bag with the help of silk secreted and

feed by remaining inside the bag.

Bag worm in Acacia

II STEM OR ROOT

BORING

Bore into the roots or stem and feed on the internal pith resulting in tunnels in the

affected region.

Teak borer

III GALL Making Feeding by an individual insect or group leads to the production of galls. In many

cases, adult or immature stage of the insect uses this gall as a shelter and derive

nutrient from the tissues.

Mite gall in Pongamia

IV BARK FEEDING Feed on stem surface leaving irregular or continues girdling on the surface. Bark feeding catepillars.

V SAP FEEDING Damage plants by making punctures and desapping resulting in chlorosis,

weakening and drying Scale insects and plant

bugs

VI ECG LAYING

DAMAGE

Punctures or slits made during egg laying make the shoots dry. Cow bugs in Acacia

MAIN PEST TYPES IN FOREST NURSERIES

ARMYWORM

These are larvae of noctuid moths.

These lay eggs on the lower surfaces

of the leaves of the host.

Defoliators

Losses of 40% of seedlings by

Spodptera sunia in nursery of Pinus

caribea, P. tropicalis and Casuarina

in Cuba (Mellado, 1976).

56% of seedlings of teak lost:

S. litura (Roychoudhury et al., 1995)

CUTWORMS

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Larvae of noctuid moth.

Soil inhabiting pests, and they cut-off

seedlings at ground level and drag

them into shallow burrows in the soil.

Moths active at night and lay eggs in

moist, recently cultivated soil, stems

and leaves of plants.

Young cutworm caterpillars climb

plants and either skeletonize the leaves

or eat small holes in them.

Agrotis ipsilon and A. segetum are

cosmopolitan and important pests of

conifers in nurseries (Sen-Sarma,

1987)

Damaged 20% seedlings of Albizia

lebbek and Eucalyptus tereticornis- A.

ipsilon (Chaturvedi, 1996, Bihar)

WHITE GRUBS

Larvae of scarab beetles damage trees

by feeding on roots, often ring-barking

and severing the stem below ground

level.

Live in soil, feeding on organic plant

matter when young and later on plant

roots.

Injury is recognized when patches of

previously healthy seedlings begin to

exhibit drought-like symptoms, thus a

faded green to brown colour and die.

These seedlings are easily pulled out

of the soil with a gentle tug.

Damaged 30% seedlings of Acacia

nilotica, Azadirachta indica and

Tectona grandis- Holotrichia serrata

and (Ali and Chaturvedi, 1996) H.

consanguinea

SCARAB BEETLES

Scarab beetle adults, and their

larvae (white grubs), defoliate

seedlings and girdle stems.

Thakur and Sivaramkrishnan

(1991) reported that 70-80 % of

the seedlings are defoliated by

cockchafer swarms in April to

May in nurseries of Eucalyptus

tereticornis, Dalbergia sissoo,

Syzygium cuminii, Peltophorum

ferrugenium and Santalum

album in Southern India.

GRASSHOPPERS AND CRICKETS

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Grasshoppers browse the foliage of young plants, and may break or sever twigs and stems.

Crickets sever stems at ground level and drag the plants into their burrows for feeding.

In Ghana, there have been regular outbreaks of Zonocerus variegatus every year in various localities (Wagner et al., 1991).

Mole crickets cause a great damage by tunneling, which disturbs the soil and sometimes uproots seedlings (Bacon and South, 1989).

In Venezula, Gryllotalpa sp. Caused losses of 20 % of young Pinus caribea seedlings in a nursery within a month of sowing (Vale et al., 1991)

DEFOLIATING CATERPILLARS

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Species of Lepidoptera.

In India, the larvae of Pyrausta machaeralis (Pyralidae) and Hyblaea puera (Hyblaeidae) are major pests of seedlings of teak.

Eligma narcissus is a major pest of Ailanthus triphysa and A. excelsa.

Young caterpillars eat the chlorophyll tissues of leaves or the tender areas near margin and older larvae leave only the mid-rib.

According to Sivaramakrishnan and Remadevi (1996), almost 100% defoliation of nursery stock of A. triphysa.

LEAF TIERS ON ROLLERS

Eggs are laid on the upper surface

of leaflets and newly emerged

caterpillars combine to web two

overlapping leaves together to

make a nest.

The caterpillars feed gregariously

and skeletonize the surface of the

leaves which then wither. The

larvae then crawl out of the

damaged leaves to the nearest pair

of suitable fresh leaves and repeat

the process. Pupation occurs in the

rolled up, withered leaves.

Damage in one Eucalyptus nursery

in Ghana exceeded 50% in some

beds (Wagner et al.,1996).

LEAF BEETLES

Chrysomela populi, a pest of

popular, beetle that chew foliage

of nursery plants causing growth

setback, deformity or mortality.

Eggs are laid in cluster on the

lower surfaces of leaves and

emerging larvae feed

gregariously at first,

skeletonizing the leaf and finally

consuming large pieces of it.

Nodostoma waterhousie, showed

infestation levels ranging from

less than 10% to almost 60%

(Singh and Singh, 1995)

WEEVILS

Weevils like Myllocerus sp. Cause

heavy injury to Acacia senegal and A.

tortilis in the Thar Desert of India (Vir

and Parihar, 1993).

Aesiotes notabilis, in Araucaria

cunninghamii seedlings, cause tunneling

in the main roots, chewing away woody

tissues as well as bark and finally

forming cocoons at or near ground level

( Brimblecombe, 1945; Elliott et al.,

1998)

LEAF CUTTING ANTS

Atta sexdens caused 71.3%

damage to rubber trees, Hevea

spp. in Brazil (Calil and Soares,

1987).

PSYLLIDS

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Sap-sucking psyllids cause

stunting, distortion, wilting,

tissue, tissue necrosis, loss of

vigour and plant death.

Their sucking causes the

periphery of the leaves to curl,

roll and later turn yellow or

brown.

Attack can result in die-back,

stunted growth, defoliation and

death.

In India, gall formation and

stunting by psyllids has been

the main problem for Albizzia

odoratissima and Pterocarpus

marsupium in nurseries in

Kerala (Mathew et al., 1991).

MEALYBUGS, SCALES AND APHIDS

MEALYBUGS- free-living insects

and their bodies may be covered with

fine powder or meal. The females are

sap-sucking and attack roots, stems,

leaves and fruits of plants.

SCALES- In TN, seedlings of the

Rhizophora mucronata were infested

by the scale Aspidiotus destructor

causing the leaves to wither and fall

(Kathiresan, 1993).

APHIDS- Cinara and Pineus are

important examples.

TERMITES

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They damage the root system

belowground level by

hollowing out or ring-barking

the tap-root, ultimately causing

death of seedling.

Thakur (1992) records 80%

mortality of Casuarina seedlings

and 10-30% mortality of Acacia

nilotica.

MANAGEMENT PRACTICES

Pest management is reducing pest problems by careful

manipulation and adoption of selected control methods.

Prophylactic methods

•Cultural methods

•Field sanitation

•Treatment with chemicals

Curative methods

•Cultural methods

•Mechanical methods

•Biological methods

•Chemical methods

•Types of Insecticides

•Botanical pesticide

Integrated Pest

Management

•Monitoring and evaluation

•Cultural and mechanical methods

•Biological control

•Chemical control

INSECT PESTS IN FOREST NURSERIES

Type Occasional pest

Description Larva occurs inside a bag made up of silk threads

secreted by larva and other extraneous materials,

mostly the spines of Acacia nilotica. Pupates within

the bag. The adult female remains inside the bag and

it is an apodorus and apterous from (without

appendages and wings) and only the male emerges as

winged moth.

Injury Defoliation

Damage The bag worm usually strips the sapling off foliage.

They prune off twigs, growing shoots and buds for

making the bags.

Occurrence May, September to October

Alternate host Tamarindus indica and Cauarina equisetifolia

Natural enemy Sinophorus psycheae

Management

measures

Mechanical

Hand picking bags and destruction can reduce the

pest

population.

Chemical : 0.05% monocrotophos spray.

Acacia nilotica

INSECT PESTS IN FOREST NURSERIES

Type Occasional pest

Description Minute light brown scales with a row of white filaments

all around the scale, occurring underneath the leaflets,

petiole and stem region

Injury Feed on plant sap

Damage Loss of plant vigor and wilting

Occurrence September to October

Management

measures

Mechanical

Plucking and destruction of affected leaves. During

early infestation stages, affected seedlings can be

segregated from the main bed and pesticides can be

applied.

Chemical: 0.06% dimethoate or 0.05% methyl demeton

can be applied during severe infestation.

Second round of spray after 15 days can be given if the

problem reoccurs.

Acacia mangium

INSECT PESTS IN FOREST NURSERIES

Type Regular pest

Description The larva, a hairy caterpillar remains concealed below

the leaves. It is bright yellow in colour with black

bands which become more prominent as it grows.

Pupation occurs in a boat shape pupal case attached on

the stem of Ailanthus seedlings. Adult is also a brightly

coloured moth with dark brown and bluish fore wings

and orange hind wings having black borders

Injury Larvae are voracious feeders and defoliate the nursery

bed

Damage Complete defoliation of seedlings result in slow or

retarded seedling growth

Occurrence October to December

Alternate host Ailanthus malabaricus, Ailanthus triphysa

Management

measures

Mechanical

integrated pest management measures

Ailanthus excelsa

INTEGRATED PEST MANAGEMENT

It involves the combination of all appropriate pest management

practics into a package which reduces the economic losses caused by

insects to tolerable levels.

Speight et al., 1999 made an attempt to summarize the types of

management that might be employed in a general IPM system for

tropical forestry.

Accordingly, the strategy consists of some stages.

Stage A deals with planning and decision making, carried out before

a tree seed is ever planted.

Stage B and C must be fully implemented as an assurance against

failure of stage A.

Stage D, the actual hands-on manipulation of insect pest

populations, comes into play once the previous stages have been

implemented. 27

STAGE A Site choice, avoid low

tree vigour; consider

life history and

previous cultivation

Tree sp or

genotype choice;

consider end-use

and economics

Location choice;

proximity to

older stands and

natural

vegetation

Silviculture choice;

mixed vs

monoculture, shade

resistance and

enrichment

STAGE B Inventory major pests

and diseases in locality;

consider history of

problems

Research

biology and

ecology of major

pest and diseases

sp; host-pest

relationships

Inventory major natural enemies in

locality-pathogens, predators and

parasitoids

STAGE C Determine potential impact damage, with

economic thresholds

Monitor pest levels during vulnerable

growth period; relate to economic

thresholds

STAGE D Ecological control:

sanitation, thinning,

nursery treatment,

establishment

Biological

control:

parasites,

predators and

parasitoides

Chemical control: insecticides, growth

regulators, pheromones

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RESEARCH AND MANAGEMENT PROBLEMS

OF USING IPM IN FORESTRY (CLARKE,1995)

PROBLEMS USING IPM IN FORESTRY

•Defining economic injury levels (EIL) of pests.

•Defining economic thresholds (ET) of pest damage.

•Carrying out monitoring procedures.

•Implementing management tactics.

•Operating under tight economic constraints 29