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Acaricidal activities of essential oil emulsions in controlling different mite pests
(2024-07-01)
Doungnapa, T.
;
Pumnuan, J.
;
Lakyat, A.
;
Thipmanee, K.
The result revealed the citronella grass emulsions had a highly toxic effect to the African red mite that presented LC50 and LC90 with 0.146 and 0.303%, respectively. While citronella grass emulsion at concentration 0.4% was able to control those 3 mite pest species in greenhouse or field conditions, when it presented the mite mortality with >80% compared with control group.
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Effectiveness of Kratom (Mitragyna speciosa Korth) leaf extracts against adult of sweet potato weevil (Cylas formicarius Fabricius) in laboratory conditions
(2024-05-01)
Ruddit, A.
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Pumnuan, J.
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Lakyat, A.
;
Doungnapa, T.
;
Thipmanee, K.
The result showed that the hexanolic leaf extract of Kratom presented rather high effect to this weevil with >70% mortality at 24 h after treatment. Besides, Kratom leaf extracted by using ethanol and acetone showed lower effect against this weevil. The hexanolic extract presented extreme toxicity to weevil with LC50 values of 3.50, 2.88 and 2.27% at 24, 48 and 72 h after treatment, respectively. This extract at 4% concentration exhibited repellency effect with > 77% significant difference compared with the control group. In addition, this extract showed high efficiency on oviposition inhibition for weevil (>89%) at 5% concentration, significantly different as compared with the control group.
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Study of insect pests and natural enemies on sticky traps in organic lettuce fields
(2024-05-01)
Lakyat, A.
;
Pumnuan, J.
;
Doungnapa, T.
;
Ruddit, A.
;
Thipmanee, K.
The results of sticky insect traps showed that chili thrips (Scirtothrips dorsalis) was the most abundance and followed by cowpea aphids (Aphis craccivora). These thrips and aphids were most found on blue and yellow sticky traps, respectively. Whereas the survey of insect natural enemies on sticky traps presented that wasp in the family Pteromalidae as well as Mymaridae and Figitidae and short-winged beetles in the family Staphylinidae were found. Those insects were mostly found on yellow sticky traps, followed by red and black sticky traps, respectively.
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Insecticidal properties of lemon grass, clove and star anise essential oils and their main chemical compounds against maize weevil (Sitophilus zeamais Motschulsky)
(2024-01-01)
Pumnuan, J.
;
Doungnapa, T.
;
Lakyat, A.
;
Namee, D.
;
Sarapothong, K.
The use of plant essential oils (EOs) as an alternative to traditional pesticides for controlling stored product pests has gained increasing attention due to the potential to reduce insecticide resistance and toxic residues in products and the environment. In this study, the EOs of lemon grass (Cymbopogon citratus), clove (Syzygium aromaticum), and star anise (Illicium verum) with their main chemical compounds were evaluated for insecticidal properties in both toxic and repellent forms against maize weevil (Sitophilus zeamais). The chemical compositions of the EOs were analyzed using gas chromatography-mass spectrometry (GC-MS). The results obtained in this study indicate that the major components in lemon grass EO are citral (84.93%; cis-citral (49.10%) and trans-citral (35.83%)), while eugenol (88.66%) and trans-anethole (95.28%) were the major compounds in clove and star anise EOs, respectively. The EOs demonstrated higher toxicity against adult maize weevils compared to their main chemical compounds. The clove EO showed the greatest fumigation potential to kill maize weevils, with an LC<inf>50</inf> of 3.044 μL L-1 air, followed by the EOs of star anise (4.925 μL L-1 air) and lemon grass (5.769 μL L-1 air). The chemical compounds eugenol, transanethole, and citral had LC<inf>50</inf> values of 4.640, 5.441, and 6.433 μL L-1 air, respectively. Lemon grass EO and citral showed their potential for repelling maize weevils, with the highest repellence response observed at a concentration of 0.12 μL cm-2 (over 75% response). Overall, this study indicates that clove EO may be effective for killing maize weevils, while lemon grass EO may be suitable for repelling this insect.
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Sweet corn seeds coating with hexane plant extracts for controlling maize weevil (Sitophilus zeamais Motschulsky) and their effect on seed qualities
(2023-01-01)
Pumnuan, J.
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Sikhao, P.
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Sarapothong, K.
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Nameea, D.
;
Doungnapa, T.
The insecticidal activity of hexane crude extracts from star anise, Illicium verum Hook.f. (HS) and clove, Syzygium aromaticum (L.) Merrill & Perry (HC) coated on sweet corn seeds, Zea mays var. rugosa against maize weevil, Sitophilus zeamais Motschulsky were evaluated in laboratory conditions. The sweet corn seeds were coated with 1, 3 and 5% hexane extracts and stored at 4°C for the period of 6 months. The insecticidal property and the effect on seed germination were evaluated after period of 2, 4 and 6 months. Various concentrations of extracts and fipronil insecticide (positive control) were tested for their efficiencies and compared with the coating agent (negative control). The result of this study showed that all hexane extract treatments gave low effectiveness to kill the adult insects, nevertheless it could completely inhibit progeny emerging. Besides, 1% of HS and HC application by using this film seed coating method presented moderate effect on seed germination after period of 6 months as it exhibited the seed germination in laboratory percentages of more than 60%. However, insect mortalities caused by hexane extracts were significantly different compared with the positive and negative control groups.
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Insecticidal activities of long pepper (Piper retrofractum Vahl) fruit extracts against seed beetles (Callosobruchus maculatus Fabricius, Callosobruchus chinensis Linnaeus, and Sitophilus zeamais Motschulsky) and their effects on seed germination
(2022-12-01)
Pumnuan, J.
;
Namee, D.
;
Sarapothong, K.
;
Doungnapa, T.
;
Phutphat, S.
Bruchid beetles (Callosobruchus maculatus and Callosobruchus chinensis), and maize weevil (Sitophilus zeamais) are important insect pests during the postharvest period. Botanical insecticide is an alternative solution for controlling these insects, and long pepper (Piper retrofractum) has been reported as having insecticidal potential against general insect pests. Film seed coatings with various concentrations of hexane extracts were made for mung bean (Vigna radiata) and corn (Zea mays) seeds. Insecticidal activities of these treatments were assessed at before and after storage period of six months, and seed germination was also evaluated. The hexane extract was subjected to analysis of the bioactive components by using Gas Chromatography-Mass Spectrometry (GC-MS). Results revealed that the hexane extract presented extreme toxicity to both bruchid beetles higher compared to maize weevil at 24 h with LC<inf>50</inf> values of 5.57–6.75 and 58.04 μg⋅cm−2, respectively. Bruchid beetles presented significant response to ethanol, acetone and hexane extracts, whereas maize weevil showed relatively low responsibility. Film seed coating with hexane extract at 1% and 3% concentrations with six-month storage presented high insecticidal activity against bruchid beetles by more than 88% mortality but had low kill rates against maize weevil. The coated mung bean seeds presented non-seed germination effect, whereas high effect was observed on coated corn. Isolation of bioactive components demonstrated that there were 74 compounds, where pentadecane was the main compound. Film seed coating technology for mung bean seed preservation by using 1% hexane extract from long pepper fruit presented to be an extremely effective method to control bruchid beetles without any seed germination effect. It could serve as one of the green insecticides of the future.

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