Chemical Ecology for Sustainable Sorghum Production in Ethiopia
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Chemical Ecology for Sustainable Production of Sorghum in Ethiopia Ylva Hillbur, Department of Plant Protection Biology, SLU ABSTRACT: The sorghum chafer can cause devastating damage in ripening sorghum. The chafer is a relatively large (2.5 cm) scarab beetle and twenty or more of them can be found on each sorghum head sucking out kernels in the milky stage. In dry-land parts of Ethiopia, where sorghum is an important staple, crop losses of up to 70% due to sorghum chafer attack have been reported. Conventional management methods have proven unsuccessful in controlling the beetle. The famers have instead developed an alternative method using rotting fruit to attract beetles to a point source of insecticide. The method is built on the fact that the beetles, like most insects, use odors to find food. Although the method is promising fruit is scarce in some regions and the odor bait is thus variable. A synthetic, standardized attractant would allow for constant use as well as for monitoring of beetle populations between regions and seasons. In a joint project between SLU and Addis Ababa University we have studied the biology and chemical ecology of the sorghum chafer and identified two highly active odor attractants. One is a host plant component discovered by electrophysiological screening of the antennal response to a wide range of known fruit and flower volatiles. The other is a pheromone component identified from extracts of the sorghum chafer females. Both compounds catch large numbers of sorghum chafers when used as odor baits in traps in the field. DISCUSSION AFTER PRESENTATION: There was a lot of interest in the project and questions concerned how many insect traps a farmer would need in order to catch enough beetle pests to be effective, and what would the cost be. The project is starting to study this element now and next year but the effectiveness depends partly on the life cycle of the pest and the timing of the trapping. It the traps can be produced cheaply enough it is anticipated that it could prove cost-effective.
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This study was presented during the conference “Production and Carbon Dynamics in Sustainable Agricultural and Forest Systems in Africa” held in September, 2010.
Transcript of Chemical Ecology for Sustainable Sorghum Production in Ethiopia
Chemical Ecology for Sustainable Production of Sorghum in EthiopiaYlva Hillbur, Department of Plant Protection Biology, SLU
ABSTRACT: The sorghum chafer can cause devastating damage in ripening sorghum. The chafer is arelatively large (2.5 cm) scarab beetle and twenty or more of them can be found on each sorghumhead sucking out kernels in the milky stage. In dry-land parts of Ethiopia, where sorghum is animportant staple, crop losses of up to 70% due to sorghum chafer attack have been reported.Conventional management methods have proven unsuccessful in controlling the beetle. The famershave instead developed an alternative method using rotting fruit to attract beetles to a point source ofinsecticide. The method is built on the fact that the beetles, like most insects, use odors to find food.Although the method is promising fruit is scarce in some regions and the odor bait is thus variable. Asynthetic, standardized attractant would allow for constant use as well as for monitoring of beetlepopulations between regions and seasons. In a joint project between SLU and Addis Ababa Universitywe have studied the biology and chemical ecology of the sorghum chafer and identified two highlyactive odor attractants. One is a host plant component discovered by electrophysiological screening ofthe antennal response to a wide range of known fruit and flower volatiles. The other is a pheromonecomponent identified from extracts of the sorghum chafer females. Both compounds catch largenumbers of sorghum chafers when used as odor baits in traps in the field.
DISCUSSION AFTER PRESENTATION: There was a lot of interest in the project and questionsconcerned how many insect traps a farmer would need in order to catch enough beetle pests to beeffective, and what would the cost be. The project is starting to study this element now and next yearbut the effectiveness depends partly on the life cycle of the pest and the timing of the trapping. It thetraps can be produced cheaply enough it is anticipated that it could prove cost-effective.
Chemical ecology for sustainable production of sorghum in Ethiopia
Ylva Hillbur, Department of Plant Protection Biology, SLU
70% crop loss, difficult to control
Sorghum chafer, Pachnoda interrupta
Fruit can be scarceVariable bait quality
Objectives:
1.Standardize the traps with synthetic plant odor lure as bait
2. Increase efficiency by adding pheromones
Different food sources – which odor signals?
Sorghum bicolor Abutilon figarianum
Odor collection
Which odor molecules do the samples contain?
Gas chromatography (GC)
GC-EAD (GC-coupled Electro Antennographic Detection)
Which odor molecules can the insect smell?
GC-EAD using beetle antennae
Antennal response to sorghum odor
1.Tridecane 2.(Z)-3-Hexenol 3.1-Octen-3-ol 4.1-Octanol
Antennal response to abutilon odor
1.(Z)-3-Hexenol 2.Tetradecane 3.Methyl salicylate 4.Methyl anthranilate
Field testing
Rasa
Embuay Bad
Field Sites
Field trapping
Wire mesh cage with bait placed here
Beetles
Wire meshcage
Sex pheromone
The trap
Odor bait
The sorghum blend: as good as its’ best component
The abutilon blend: as good as its’ best component
• Single compounds good attractants
• Screening of several compounds by single sensillum recordings
Locationof sensilla=Odor detectingsensory hairs
Single sensillum recordingwith odor stimuli
Stimulus: substance that activates neuron
1 sec 2 3 4
Single sensillum recording
Field trapping – plant odors
• Strong attraction to 2,3-butanediol
Do sorghum chafers use pheromones?
Wire mesh cage with bait placed here
Beetles
Wire meshcage
Sex pheromone
Wire mesh cage with bait placed here
Beetles
Wire meshcage
Banana
Aggregation pheromone
Field trapping – live insectsMean trap catch over four days
0
10
20
30
40
50
60
Unm.F Mated F M M+F Unm.F+Food
M +Food M+F +Food Food Control
malesfemales
Unmated females attract males
Field trapping – live insectsMean trap catch over four days
0
10
20
30
40
50
60
Unm.F Mated F M M+F Unm.F+Food
M +Food M+F +Food Food Control
malesfemales
Mated females or malesare not attractive
Field trapping – live insectsMean trap catch over four days
0
10
20
30
40
50
60
Unm.F Mated F M M+F Unm.F+Food
M +Food M+F +Food Food Control
malesfemales
Combining unmated females with
food increasesattraction
Pheromone identification
• Multiple extractions of males and females
• Comparison of odor profiles
Pheromone identification
• Multiple extractions of males and females
• Comparison of odor profiles
19 female-unique compounds
Field trapping -female compounds
Field trapping -female compounds
• Phenylacetaldehyde very attractive to both sexes
Future plans
• Field testing of blends SUPERLURE!• Lures with high longevity• Cheap & efficient traps
Jonas Yitbarek Bekele Emiru Stefan Satya Gitachew Merid
Gashebesaw & the field team
Collaboration: Ministry of Agriculture, Addis AbabaFunding: Sida / SAREC
