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Details: Category: Pests | Published: 18 June 2013 | Hits: 3061

Introduction

Major  rice pests of rice in Kenya

I. Insect Pests of Rice (Oryza sativa)

1. Rice stem borers white stem borer, pink stem borer, striped stem borer and stalk eyed fly
 
Distribution: The rice stem borer occurs in all rice growing areas in Central, western, Nyanza and Coastal regions

Nature of damage:  The presence of drying  central shoot called ‘dead heart’in young plant or drying of the panicle called ‘white head’in older plants.

Management Strategies:

  1. Removal and destruction of rice stubbles from field and also collection and destruction of egg masses.
  2. Clipping the tip of the seedlings prior to transplantation to eliminate egg masses.
  3. Collection and destruction of moths using light traps.
  4. Spraying of fenthion or fenitrothion or endosulfan or phosalone or monocrotophos or etofenprox or cartap hydrochloride or chlorpyriphos or phenthoate at 0.5 kg a.i./ha or fipronil 5% SC at 1 litre/ha if the economic threshold level of 10% dead heart is crossed in the nursery a week prior to pulling out the seedlings and the second after 15 days of transplantation.
  5. An economic threshold level of 10% dead heart in vegetative stage and presence of 1 moth or 1 egg mass/sq.m. in the ear-head bearing stage has been suggested for adoption of chemical method of control by giving a third spray with one of the above chemical pesticides.
  6. Seedlings root dip treatment for 12 or 14 hours before transplanting in 0.02% chlorpyriphos gives protection upto 30 days against stem borer.

Conservation of natural enemies such as Spiders,Dragon flies,Ladybird beetles, Predatory wasps and  Parasitic wasps

2. Rice gall midge

Distribution: It is found in South Nyanza Bunyala irrigation scheme.

It also breeds on a number of grasses.

Nature of damage : The gall formed by this fly is popularly known as ‘silver shoot’ or ‘onion shoot’ because of the formation of hollow pink or purple, dirty white or pale green cylindrical tubes bearing at their tips a green reduced leaf blade complete with ligules and auricles. It infests the rice even in the nursery but usually tillers are preferred

Management Strategies:

  1. Seed treatment with chlorpyriphos 0.2% emulsion for 3 hours or seed mixing with either chlorpyriphos (0.75 kg a.i./100 kg seeds) or imidacloprid (0.5 kg a.i./100 kg seeds) provide protection for 30 days in the nursery.
  2. Seedling root dip in 0.02% chlorpyriphos emulsion before transplanting for 12 -14 hours gives protection for 30 days.
  3. Removal and destruction of weeds that serve as alternate host plants.

 

Conservation of natural enemies such as Spiders, Dragon flies, Ladybird beetles, Predatory wasps and Parasitic wasps

3. Green rice leaf hoppers

Distribution: These insects are found distributed in all rice growing areas in Kenya. The insect is active during July – November in different regions.

Nature of damage: Both nymphs and adults suck the plant sap and cause browning of leaves. Both the species are known to be vectors of virus diseases of rice such as rice yellow mottle virus.

Management Strategies:

(i) Spray application of phosalone or etofenprox or cartap hydrochloride or monocrotophos or acephate or chlorpyriphos or carbaryl, at 0.5 kg a.i./ha or fipronil at 50 g a.i./ha or application of granular insecticides such as phorate or sevidol or cartap hydrochloride or carbofuran at 1 kg a.i./ha or fipronil 0.3% G at 25 kg/ha.

Conservation of natural enemies such as Spiders,Dragon flies,Ladybird beetles, Predatory wasps and  Parasitic wasps

4. Brown plant hopper

Distribution: Found in all rice growing regions.

Nature of damage: It infests the rice crop at all stages of plant growth. Due to feeding by both nymphs and adults at the base of the tillers, plants turn yellow and dry up rapidly. At early infestation, round yellow patches appear which soon turn brownish due to the drying up of the plants and this condition is called ‘hopperburn’. N. lugens is a phloem feeder. Very high infestation causes lodging of the crop resulting in yield loss ranging from 10 - 70 %.

Management Strategies:

(i) Spraying carbaryl (0.75 kg a.i./ha) or etofenprox, moncrotophos*, phosalone* or chlorpyrifos* @ 0.5 kg a.i./ha or lindane 20 EC at 1 litre/ha in the early stages of the crop.
(ii) Application of granules of carbofuran at 0.75 kg a.i./ha or phorate at 1.25 kg a.i./ha.

* Application should be restricted to early stage of the crop.

Conservation of natural enemies such as Spiders,Dragon flies,Ladybird beetles, Predatory wasps and  Parasitic wasps

5. Rice leaf folder

Distribution: Occurs in all rice growing areas of our country.

Nature of damage: The larva rolls the leaf blade by fastening its edges and sometimes even fastening the leaf tip to the basal part of the leaf blade and feeds from inside by scraping. In a severely infested field the whole crop gives a sickly appearance with white patches. The infestation at boot leaf stage of the crop sometimes results in heavy loss of grain yield.

Management strategies:

(i) Removal of grass from field bunds.
(ii) Need based spraying of phosalone or carbaryl or monocrotophos or etofenprox or cartap hydrochloride or quinalphos or fenthion at 0.5 kg a.i./ha or spray of fipronil 5 SC at 1 litre/ha.

Conservation of natural enemies such as Spiders, Dragon flies, Ladybird beetles, Predatory wasps and parasitic wasps
 
6. Rice earhead bug
Distribution: This is one of the important pests of rice appearing before the flowering stage and continuing up to the milky stage. Apart from rice it also breeds on a variety of grasses.

Nature of damage: Both the nymphs and adults feed on the sap of panicle, tender stem and milky grains making them turn chaffy.

Management Strategies:
(i) Dusting carbaryl 10 %, and repeat it depending upon the severity of infestation.

7. Whorl maggot
Distribution: It occurs in irrigated rice growing areas in Kenya.

It also breeds in grass weeds such as Cynodon dactylon, Echinochloa crusgalli, E. colona, Fimbristylis miliacea, Eleusine indica and Paspalum scrobiculatum.

Nature of damage: The maggots attack the leaf blades even before unfurling and the initial damage is characterised by the presence of narrow stripes of whitish area in the blade margins. The tillers become stunted. Damaged leaves become distorted and may break off in the wind.

Management Strategies:
(i) Spraying of endosulfan or quinalphos or fenthion at 0.5 kg a.i./ha
(ii) Alternatively, application of granules of carbofuran or fenthion at 0.75 kg a.i./ha.

Conservation of natural enemies such as Spiders,Dragon flies,Ladybird beetles, Predatory wasps and  Parasitic wasps
 
8. Termite- the root feeder
Distribution: Termites are found in all upland rice growing.. They are polyphagous and have the widest range of host plants. They devour not only the live plant material but also the dead wood.

Nature of damage: Termites attack rice at the time of sowing onwards and the damage is severe in sandy and sandy-loam soils. It cannot thrive under conditions of bad aeration and poor

Management strategies:
(i). Destroy termitaria (termite mounds) in the vicinity of fields and treat the spot with sprays. This should be practiced on community basis in villages/farms.
(ii). Use only well rotten manure, otherwise termite incidence is aggravated.
(iii). Treat the seeds of rice with chlorpyriphos or endosulfan or imidacloprid using, respectively, 90 and 240 ml and 10 ga. i. with 5 litres of water and spraying over one quintal seed spread on floor and periodically turned over to ensure proper treatment. This should be done 1 - 2 days before sowing. For sowings in fields having previous history of termite incidence, this operation should invariably be undertaken.
(iv). In case preventive seed treatment for termites has not been undertaken before sowing and termite incidence is noticed in standing crop of rice, mix 0.8 liter chlorpyriphos with 50 kg sand and broadcast in one hectare field. This treatment is not as effective as seed treatment but appreciable reduction in termite damage could be achieved.
(v) Subterranian termites can be controlled by destroying queen either by digging it out or pouring chlorpyriphos 20 EC.
Conservation of natural enemies such as entomopathogenic fungi and bacillus , Spiders,Dragon flies,Ladybird beetles, Predatory wasps and  Parasitic wasps
 
Rice Leaf mining beetles
Leaf scrapers are generally present in moderate numbers and habitually cause relatively minor damage. However, in certain instances they can represent a really serious threat to a crop. Chrysomelid beetles are vectors of RYMV

Mole Cricket:
Infests dried paddy field or rain fed field.
Both nymphs and adult feed on root and shoot near the ground

Management
Soil application of insecticides.
Flooding avoids cricket infestation

Golden Apple Snail
Is a minor pest, causes damage in low-lying portions of newly transplanted rice fields
Missing seedlings and floating cut leaves characterised this damage

Nematodes
Nine nematode genera are reported in rice fields in Kenya but all had low population numbers
Causes drying and wilting of plants and Presence of gall on the rooots

Rice natural enemies
Spiders, water bug, frog, mired bug, damsel fly, dragon fly, grasshopper, coccinelids, bracon, wasps, Trichogramma, Telenomus

IPM is “a pest management system that, in the context of associated environment and population dynamic of the pest species, utilizes all suitable techniques and methods in as compatible manner as possible and maintain the pest population at levels below those causing economic injury”.

Integrated pest management strategy for rice pests

Cultural practices
Selection of healthy seed or resistance/tolerant variety
Raising healthy nursery
Early and timely sowing/planting
Seedling root dip/nursery treatment in stem borer endemic area
Destruction of left over nursery
Normal spacing
Balanced use of fertilizer
Proper water management (alternate wetting and drying to avoid water stagnation in plant hopper endemic areas
Harvest close to the ground.

Mechanical practices:
Clipping off rice seedling tips before transplanting
Removal and destruction of disease/pest infested plant parts.
Use of rop in rice crop to dislodge caseworm and leaf folder larvae etc.
Collection and destruction of egg mass and larvae.

Biological control practices:
Conservation.
Biological agent such as spiders, water bug, frog, mired bug, damsel fly, dragon fly, grasshopper, coccinelids, bracon, wasps, Trichogramma, Telenomus etc should be conserved
Root dip treatment of rice seedling with chloropyrifos is safer for natural enemies.
Augmentation release of biological control agents

Chemical control measures
Chemical pesticides are to be applied on need base and judiciously
Recommended chemicals are to be applied at right time at recommended dose.
Weed Management practices
Seed bed should be prepared thoroughly ensure through land preparation of field. Proper puddling and harrowing to be give and to ensure uniform water stagnation
Timely sowing of the crop
Sowing at proper spacing.
Mechanical weeding should be practiced 2-3 week and so on if necessary.
Bunds and irrigation channels should be kept weed free.

Rodent Management.
Bund trimming and weed free cultivation minimizes rodent herbage
Employment of indigenous trap etc
Application  of rodenticides such as Zinc phosphide, Aluminium phosphide as and when required.