Abstract
Food situation has remained insecure and unpredictable in sub-Saharan Africa, leading to high levels of cyclic famine and poverty. This has been exacerbated by perennial pest problems, which cause substantial post-harvest food grain losses. It is against this background that this study was designed to investigate the use ofHyptis spicigera preparations for pest control and hence generate effective biological control options compatible with the prevailing farmers’ circumstances. Laboratory and on-farm studies were conducted in order to assess the insecticidal potency of H. spicigera extracts on maize weevils, Sitophilus zeamaisMotschulsky (Coleoptera: Curculionidae) and red flour beetle (Tribolium castaneum Herbst (Coleoptera: Tenebrionidae). Fumigant toxicity was assessed at four rates (0, 2, 4, 6, 8, 10 μl/l air) in space fumigation whereas repellence was evaluated in choice bioassay system at five rates (0, 0.2, 0.4, 0.6, 0.8 and 1.0% w/w). Contact toxicity was evaluated by the perforated jar method using dry powder, fresh leaves and oils while antifeedant activity was studied by the flour disk method. The results established that both whole plant parts and steam-distilled essential oil extracts possess strong insect repellent activity at reasonably low doses. Following exposure of newly emerged adult insects to 12 h of fumigation using essential oils at a dose of 25 μl/vial, 70% mortality was recorded for H. spicigera and 0% in the control. Whole plant powder had high potency compared to polar extracts which were not significantly efficacious to the insects.Hexane extract also showed the highest feeding deterrence activity compared to either ethyl acetate or water extracts. Hyptis oil extract on maize was also the most effective treatment at reducing insect infestation and seed damage compared to other treatments in the field. Whole plant extracts and essential oils described could be useful for managing field populations of S. zeamais and T. castaneum. Therefore, this study introduces an innovative approach to the use of traditional plant-based pesticides for grain protection in Kenya. Key words: Hyptis spicigera, bioactivity, antifeedant, toxicity, repellancy, stored-product insects.
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Claims 8
Claim · model-written summary
Whole plant parts repelled storage insects strongly at low doses.
- Treatment
- whole plant partse0
- Outcome
- strong insect repellent activitye0
- Direction
- stronge0
- Qualifier
- reasonably low dosese0
Zea maysNot reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“both whole plant parts and steam-distilled essential oil extracts possess strong insect repellent activity at reasonably low doses.”
t0“maize grains”
Claim · model-written summary
Steam-distilled essential oil extracts repelled storage insects strongly at low doses.
- Treatment
- steam-distilled essential oil extractse0
- Outcome
- strong insect repellent activitye0
- Direction
- stronge0
- Qualifier
- reasonably low dosese0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“both whole plant parts and steam-distilled essential oil extracts possess strong insect repellent activity at reasonably low doses.”
t0“maize grains”
Claim · model-written summary
H. spicigera essential oil caused 70% adult insect mortality after 12 hours versus 0% in control.
- Treatment
- essential oils at a dose of 25 μl/viale0
- Outcome
- adult insectse0
- Value
- 70%e0
- Qualifier
- 0% in the controle0
- Comparator
- the controle0
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Following exposure of newly emerged adult insects to 12 h of fumigation using essential oils at a dose of 25 μl/vial, 70% mortality was recorded for H. spicigera and 0% in the control.”
t0“maize grains”
Claim · model-written summary
Whole plant powder had higher insecticidal potency than polar extracts.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Whole plant powder had high potency compared to polar extracts which were not significantly efficacious to the insects.”
t0“maize grains”
Claim · model-written summary
Polar extracts were not significantly efficacious against insects.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“polar extracts which were not significantly efficacious to the insects.”
t0“maize grains”
Claim · model-written summary
Hexane extract had the highest feeding deterrence compared with ethyl acetate or water extracts.
- Treatment
- Hexane extracte0
- Outcome
- feeding deterrence activitye0
- Direction
- higheste0
- Comparator
- ethyl acetate or water extractse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Hexane extract also showed the highest feeding deterrence activity compared to either ethyl acetate or water extracts.”
t0“maize grains”
Claim · model-written summary
Hyptis oil extract on maize reduced insect infestation most effectively in the field.
- Treatment
- Hyptis oil extracte0
- Outcome
- insect infestatione0
- Direction
- reducinge0
- Comparator
- other treatmentse0
- Setting
- the fielde0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Hyptis oil extract on maize was also the most effective treatment at reducing insect infestation and seed damage compared to other treatments in the field.”
Claim · model-written summary
Hyptis oil extract on maize reduced seed damage most effectively in the field.
- Treatment
- Hyptis oil extracte0
- Outcome
- seed damagee0
- Direction
- reducinge0
- Comparator
- other treatmentse0
- Setting
- the fielde0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Hyptis oil extract on maize was also the most effective treatment at reducing insect infestation and seed damage compared to other treatments in the field.”
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botanical · pest · Zea mays (maize)Positive and negative results
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