A COMPARATIVE STUDY OF COLOR SENSITIVITY COMBINED WITH OPENED AND

PROTECTED TRAPS FOR INSECT PEST MANAGEMENT IN CHINESE KALE (Brassica

oleraceae L.)

ByV.N. Wickramaarachchi (106296)

Agricultural Systems & EngineeringSchool of Environment, Resources and Development

Asian Institute of Technology, Thailand

Thesis Advisor : Dr. S.L. Ranamukhaarachchi

Motivation...

Demands excessive use of pesticides (Indiscriminate use) Demands excessive use of pesticides (Indiscriminate use)

Consumers consume Pesticide contaminated

vegetables

Consumers consume Pesticide contaminated

vegetables

Disrupt delicate balance Between insect pest and

natural enemies

Disrupt delicate balance Between insect pest and

natural enemies

Integrated Pest Management (IPM)Integrated Pest Management (IPM)

Uses combination of complementary methodsUses combination of complementary methods

Year round cultivationYear round cultivation

Increases pest insidence, continuation severity of damage Increases pest insidence, continuation severity of damage

Use of color traps in various ways

Colored objects

Colored mulches

Color lights

Most Commonly Used Color Traps

General objectiveTo determine the performance of different

color based modified traps and their efficacy for enhancing insect pest attraction and

conservation of natural enemies

Problem statementLure insect pests along with the beneficial insects (natural enemies)

Experimental design

Treatments (10)

Complete Randomized Design (CRD)

Yellow, white, red color cards combined with

• glue alone

• glue + protective mesh

• without glue nor protective mesh

• control (no color card)

Four replicates

Treatment coding systemX X X

Colour of the trap

Y – Yellow W – White R – Red

Glue coating

0 – without glue G – with glue

Protective cover

0 – No cover

P – with cover

Opened sticky color trap model Protected sticky color trap model

Reflectance pattern from mature and immature leaves

Reflectance pattern from color cards

(a) Without glue (b) With glue (c) With protective

net structure

Similar reflectance pattern

Higher reflection in Immature leaves (yellow)

Lower reflection in Mature leaves (dark green)

(b) With glue

Cabbage aphid

Stripped flea beetle

Attraction for yellow colour is significant

Significant effect through out the observation period and yellow shows highest mean

Cluster caterpillar

Diamondback moth

Both yellow and white attracted, but ot red

No specific color response

Thrips

Fungus gnats

Found in large numbers each color card

Red attracted most

Lady bird beetle

Yellow colour shows dominent effect Color card traps with protective mesh trapped only few LB’s They could be protected

Lacewing

Parasitic wasp

Green lacewings are common

Yellow and white attracted most

Highest attraction on 3-4 weeks

Not sensitive to red colour

Population dynamics of insect pestsp

es

t co

un

t in

cre

as

es

Fungus gant - Significant rate of development

Reduction of green lacewing

Flea beetle - population increased

All natural enemies remains constant from the 5th week onwards (except lady beetle)

Lady beetles found in large numbers

Cabbage aphids & Lady beetles

Lady beetles (main predators for aphids) are voracious feeders (adult lady beetle consumes around 50 aphids per day)

Cabbage aphid density is relatively higher than lady beetle, to facilitate lady beetles to be performed effectively (Ferguson, 2005 online) .

Apart from that modified sticky trap also contribute (80 % of natural enemies are protected with the protected net structure)

Good example on natural biological control in the crop field.

Other examples……….

Spider with its prey inside the web

Ant feeding on aphids

Is it effective?

57% reduction in captured insects to the YGP traps, but same time 85 % of reduction in natural enemies

WGP shows 44% and 87% reduction in insect pests and natural enemies respectively.

RGP does not show similar trends as yellow and white traps

Great improvement in the natural enemy conservation point of view

But the capturing of insect pests by the modified sticky trap is reduced around 50% than that of traditional sticky colour trap. Why……….

Net size and net structure may disturb the pest movement towards the sticky trap thereby they move away from the trap.

Chinese kale leaf infestation level

Total harvested and damage yields

Control plot – Avg. damaged yield is higher, leaf infestation lower values Control plots are surrounded by plots

having color cards Damage done by pests who are

survive Latter stage – damage in control plot

high because of high pest population and limited food

At harvest –quantity of damage high

Early harvesting Uncontrolled sampling errors

YG0 – highest yield, YGP –lowest pest damage

Due to planting density difference Total yld (stem, good leaf,damage leaf wt) Weight distribution different

Total yield is not significantly different

1/ Average total yield (t/ha)2/ Average damage yield (t/ha)3/ Average within the column followed by the same letter are not significantly different

Non- sticky trap performance vs. control Cabbage aphid wingless forms colonize

mostly in the lower part of the leaf. Highest aphid & Flea beetle population

in yellow cards, lowest in red cards Squash bug – high in red cards Control plot had the highest pest

population. Plots with yellow cards had the

maximum of Lady beetles.

Highest crop damage in control site

Natural biological control process in plots with colour

cards is functioning effectively (Y00,W00,R00

lower damage yield compare to control)

Conclusions

Use of the yellow, white and red cards was found effective in reducing pest populations and increasing natural enemy population in Chinese kale

The protected mesh showed slight reduction in the insect pests trapped, and a greater reduction in the number of natural enemies on glued color cards

The number of insects and damaged yield were lower in plots provided with red color indicating that it has a repellence effect

Yellow performed well in all color cards in terms of attracting the highest number of insect pests and natural enemies, but final marketable yield remained unchanged, yet the control had the lowest. This indicates the efficacy of using color sensitivity for managing insect pests in Chinese kale

Recommendations

Conducting further studies with different protective mesh sizes that could facilitate the movement across the net for insect pests and discourage the passage of natural enemies

Considering the extent of cultivation, the optimum size and the number of traps could be determined with further studies

Use of modified sticky trap integrated with pest repellent plants

It would be useful to develop a method that could not only capture those insects, but also to capture live, because sweep net method was not applicable for these low moving insects and also for caterpillars and finally they could be used for further studies