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Plant extract-based nanoemulsion for controlling sweet potato pests and weeds
(2026-12-01)
Pumnuan, Jarongsak
;
Ruddit, Anusart
;
Lakyat, Anuwat
;
Doungnapa, Thanaporn
;
Deemak, Jantra
The sweet potato weevil (Cylas formicarius) is the most destructive pest of sweet potato and is often associated with diseases and weeds. The use of plant extracts as pest control agents is a promising, eco-friendly approach, but their effectiveness often declines under field conditions. Therefore, nanoemulsion technology was applied to improve the dispersion and bioefficacy of active compounds. In this study, we aimed to develop plant extract-based nanoemulsions as multifunctional biopesticides capable of controlling insect pests, fungal pathogens, and weeds. Twenty-one plant extracts were screened for their effects adult SPW via contact methods. The most potent extracts were then formulated into nanoemulsions and evaluated for insecticidal efficacy—including contact toxicity, repellency, and oviposition inhibition. In addition to insecticidal effects, antifungal and herbicidal activities were systematically assessed against Fusarium sp. and two common weed species in sweet potato fields, Amaranthus tricolor and Echinochloa crus-galli. The major chemical constituents of key extracts were identified using gas chromatography–mass spectrometry (GC–MS). Among all extracts, the hexane extracts of star anise and long pepper exhibited the highest contact toxicity, with LC50 values ranging from 2.051 to 2.415% at 24 h. When formulated into nanoemulsions (NHEF-1 and NHEH-2), toxicity increased 16- to 18-fold, lowering LC<inf>50</inf> values to 0.114–0.150%, and at above 0.1%, oviposition was inhibited by more than 85%. Both formulations also demonstrated significant antifungal activity against Fusarium sp. (44.6–56.8% growth inhibition) and completely inhibited the germination of A. tricolor (at 0.01%) and E. crus-galli (at 1.0%). GC–MS analysis revealed anethole (84.49%) as the predominant compound in the star anise extract, with long pepper extract containing moderate amounts of several compounds. These findings demonstrate the potential of plant extract-based nanoemulsions as eco-friendly, multifunctional biopesticides for sustainable sweet potato management, integrating enhanced insecticidal, antifungal, and herbicidal effects.
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Antifungal Activity and Phytochemical Analysis of Myrtaceae Leaf Extracts including the Induction of Defense Enzymes in Lettuce against Alternaria Leaf Spot
(2025-01-01)
Somnuek, Suriyasit
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Thipmanee, Kamronwit
;
Jaenaksorn, Tanimnun
To avoid the risk of harmful effects from synthetic fungicides on human and natural environments, our study aimed to evaluate the potential use of the indigenous Thai Myrtaceae plants as a harmless means for controlling the plant diseases. Four Myrtaceae extracts showed no phytotoxicity towards lettuce cultivated in hydroponic conditions, with notable plant-growth-promoting potential observed in lettuce treated with Callistemon viminalis (EECV). With regard to a direct effect, Melaleuca cajuputi (95% EEMC) showed the strongest inhibition of mycelial growth of A. brassicicola (85–100%), followed by 95% EECV (40–63%), while both extracts significantly inhibited spore germination (80–100%). A GC/MS and LC/MS analysis revealed terpenoids as the predominant compounds at approximately 55% and 37% in EEMC and EECV, respectively, with high concentrations of phytol (14%) and 1,8-cineole (14%) being particularly notable. As an inducer of an indirect effect of the plant extracts, the results from the experiment with 95% EEMC (15,000 and 50,000 ppm) as well as 50 and 95% EECV (15,000 and 50,000 ppm) applications was in good agreement, demonstrating significant reductions in disease severity in hydroponically grown lettuce ranging from 50 to 70% together with the induction of defense enzymes (specifically β-1,3-glucanase, chitinase, and peroxidase) compared to those in the inoculated control and fungicide treatment groups. Furthermore, a correlation analysis revealed a negative correlation between disease severity and the three defense enzymes. Our findings underscore the considerable efficacy of the three botanical fungicides tested here (i.e., 95% EEMC as well as 95% and 50% EECV) for the management of Alternaria leaf spot in lettuce.
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Cross-Resistance to Benzimidazole Group and Mancozeb Fungicides in Colletotrichum spp. Causing Anthracnose Disease
(2022-10-01)
Kongtragoul, Pornprapa
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Somnuek, Suriyasit
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Udompongsuk, Mongkutkarn
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Prasom, Panisa
;
Jaenaksorn, Tanimnun
Anthracnose is considered to be one of the most serious diseases for major crops cultivated in Thailand. Although chemical fungicides and newer chemicals have been recommended and used for disease management, it is still difficult to control. Thus, the monitoring of fungicide resistance development is required and very important for the success of disease control strategies. In this study, a total of 34 isolates of Colletotrichum spp. were successfully collected from anthracnose diseased plants in central Thailand. Of these isolates, 16 were collected from mango, and 2 from crinum lily or orchid and were morphologically identified as C. gloeosporioides, while the other 16 isolates from chili were morphologically identified as C. capsica. Then, all isolates were evaluated in vitro against 3 fungicides to determine their sensitivity. The results showed that 25 isolates were cross-resistant to both benomyl and carbendazim, as the 50% effective concentration (EC<inf>50</inf>) of each fungicide was >100 mg L<sup>-1</sup>. All isolates were resistant to mancozeb. Nine out of 16 isolates from mango anthracnose were confirmed as C. gloeosporioides by the sequence of internal transcribed spacer (ITS) and 5. 8S regions of rDNA. Eight cross-resistant isolates were not controlled by the treatment with 100 mg L<sup>-1</sup> of benomyl or carbendazim on ‘Nam Dok Mai’ mango fruits, but sensitive isolate was better controlled at 79.33% and 85.11%, respectively. Our results indicated that cross-resistant strains are present in the populations of anthracnose fungi in central Thailand.
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Effect of crude ethanolic extracts from bottle brush (Callistemon viminalis) against leaf spot fungi and their phytotoxicity on lettuce (lactuca sativa l.)
(2020-01-01)
Somnuek, Suriyasit
;
Jaenaksorn, Tanimnun
;
Laosinwattana, Chamroon
In response to the public concern about environmental problems as well as fungicide residues on agricultural produces especially leaf vegetables, we investigated the potential use of crude extracts from bottle brush (C. viminalis) leaves against leaf spot fungi and their phytotoxicity on lettuce grown in hydroponics. Yield, total phenolic and flavonoid contents of the extract were also evaluated. Regarding the in vitro antifungal assay using poisoned food technique, 3×3 factorial in Completely Randomized Design (CRD) was employed with three replicates. Factor A was 3 crude extracts (50% ethanol, 70% ethanol and 95% ethanol crude extract) while factor B was the 3 concentrations (0, 5,000 and 50,000 ppm) of crude extracts. Results showed that all three crude extracts were significantly effective in inhibiting the mycelial growth and sporulation of leaf spot fungi (Alternaria sp. and Curvalaria sp.). There was a significant interaction between all extracts and their concentration regarding inhibition percent. Increase in crude extract concentrations resulted in a marked increase in their inhibition. The 50,000 ppm gave the highest effectiveness. For phytotoxicity test, all tested crude extracts did not give any negative effects either on seed germination or growth of lettuce grown in hydroponics. Interestingly, growth promotion about 30 percent was achieved on this regard. Based on quantitative assay, the highest yield of crude extract was obtained from 95% ethanol solvent. Highest total phenolic and flavonoid contents were detected at the highest concentration of all crude extracts.
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