| Plant essential oils are widely used to control insect pests, they have repellent, oviposition deterring, fumigant and contact activities against insect pests. Essential oils usually are less toxic to non-target pests than chemical pesticides. Therefore, essential oils could be an alternative for chemical pesticides. In the current study, ethanol-extracted essential oils were obtained from 14 aromatic, spicy, and medicinal plant species. We examined their repellency, oviposition deterring, fumigant, and contact activities against pests in greenhouse, stored-product and human habitation, at the concentration of 10,000, 5,000,2,500, 1,000 and 100 ppm. We found that 10000 ppm has good activity against pests. The main results are as follows:1. The effects of plant essential oils against greenhouse insect pests1.1 Repellant and oviposition deterrence activities against Bemisia tabaciThe repellency and oviposition deterrence activity of essential oil from Acorus tatarinowii,Stemona japonica, Gardenia jasminoides, Myristica fragrans, and Heracleum hemsleyanum,Piper nigrum, Curcuma longa, Litsea cubeba,and Zanthoxylum bungeanum against Bemisia tabaci were examined in lab and greenhouse. In the laboratory experiment, the maximum repellency (76.71%) was observed in association with M. fragrans at 24 h, and the maximum oviposition deterrence (68.46%) was observed in association with C. longa at 24 h. Z. bungeanum showed minimum repellency(19.80%) at 48 and minimum oviposition deterrence (4.22%) at 24 h. In the greenhouse experiment, M. fragrans showed the maximum repellency (58.33%) and anti-oviposition(46.11%) with 10,000 ppm concentration at 24 h. Essential oils from C. longa showed minimum repellency (17.03 %) at 48 h and minimum oviposition deterrence (8.31%) at 24 h of exposure.1.2 Repellant activity against glycinesThe repellency activity of essential oil from A. tatarinowii, Mentha haplocalyx,S.japonica and mixture of A. tatarinowii + S.japonica oils against aphid were examined in lab and greenhouse experiments. A mixture of A. tatarinowii + S. japonica oils demonstrated maximum repellency (71.25%) at 6 h of exposure in lab and (85.61%) at 12 h of exposure in greenhouse. Strong anti-molting activities were observed in the essential oil of S. japonica.1.3 Fumigant activityThe fumigant effects of essential oil from A tatarinowii, S. japonica, G. jasminoides, M.fragrans and H. hemsleyanum were examined against B. tabaci adult in the lab. All the essential oils proved to have fumigation abilities on adult B. tabaci. At the concentration of 10,000ppm, 8 h after initiation, the maximum mortality was 98.81%, which was caused by A. tatarinowii, and the minimum mortality (22.14%) was associated with H.hemsleyanum.1.4 Contact activityEssential oil from A. tatarinowii, S. japonica, G. jasminoides, M. fragrans and H.hemsleyanum, exhibited contact toxicity against B. tabaci (adults or nymphs). The maximum contact toxicity (95.62% mortality) was associated with A. tatarinowii at 8 h post-treatment with 10,000 ppm in the laboratory, whereas the maximum mortality(80.75%) observed at 48 h under greenhouse conditions. S. japonica showed 51.88%mortality at 24 h in the laboratory and 69.50% mortality at 48 h in the greenhouse.2. Activities of compounds identified from essential oil against greenhouse pestsWe use GC-MS to identify the main chemicals in essential oils. Then we select four compounds including squalene, ethyl linoleate, n-hexadecanoic acid, and 9-12-octadecadienoic to evaluate the activity of them on whiteflies and mites.2.1 Repellant activity against whiteflyAll four compounds showed strong repellency against whitefly adults. In the greenhouse experiment, squalene showed maximum repellency against whitefly adults at 24 h(89.59%), and 9-12-octadecadienoic acid showed minimum repellency at 24 h (59.24%).2.2 Fumigant activity against whiteflySqualene showed maximum fumigation toxicity (47.20% mortality) at 3 h against whitefly adults, whereas the n-hexadecanoic acid showed minimum fumigation (21.55%mortality) at 1 h against whitefly adults in lab.2.3 Contact activity against whiteflyEthyl linoleate showed maximum contact toxicity at 3 h (41.13% mortality) and also the minimum at 9 h (15.63% mortality) against whitefly nymphs in lab experiment. In the greenhouse experiment, squalene showed maximum whitefly nymphal toxicity at 24 h(80.08%).2.4 Contact activity against miteIn greenhouse experiment, Squalene showed maximum contact toxicity against mite adults (46.81% mortality) and mite nymphs (56.11% mortality) at 3 h of exposure. n-hexadecanoic acid showed minimum contact toxicity at 3 h (19.83%) against mite adults and 9-12-octadecadienoic showed minimum contact toxicity (26.07%) at 1 h of exposure against mite nymph. In the greenhouse experiment, squalene showed maximum toxicity to adult mite at 24 h (78.74%). Also, ethyl linoleate showed maximum toxicity at 24 h(72.28%) against mite nymphs. ethyl linoleate showed minimum toxicity at 48 h (41.13%)against adult mites, and n-hexadecanoic acid showed minimum toxicity at 48 h (30.37%)against mite nymphs.3. The effects of plant essential oils against stored grain insect pests3.1 Repellent activityThe repellency activity was of essential oils from Cedrus atlantica, Mentha piperita,Santalum paniculatum, H. hemsleyanum, M. haplocalyx and S. japonica were examined against red flour beetle. Heracleum hemsleyanum showed strong repellency, with values of 94% at 12 h, whereas S. japonica showed attractancy with values of 53.75% at 72 h of exposure, against red flour beetle in petri dishes. whereas, C. allantica showed maximum repellency (83.75%) at 1 d and minimum repellency (25.00%) at 7d of exposure in H type tube.The repellency effects of essential oil from Cinnamomum camphora, P. nigrum and S.japonica were observed on saw-toothed beetle. Cinnamomum camphora essential oil was the strongest repellent (83.75%) at 12 h and S. japonica showed weak repellency (56.14%)at 96 h of exposure.The repellency of essential oils from Allium ascalonicum and M. haplocalyx were examined against (adults and larvae) maize weevil. M. haplocalyx showed maximum repellency of adults (67.50%) and grubs (67.50%) at 6 h of exposure and the minimum repellency was observed from A. ascalonicum against adults (66.25%) and grubs (63.75%)at 6 h of exposure.3.2 Fumigant activityThe fumigant effects of essential oil from C. atlantica, M. piperita, and S. paniculatum,were observed against larval stage of red flour beetle. The maximum fumigation (49.67%)was observed at 8 h with the oil of M. piperita, and no fumigation effects were observed with C. atlantica oil at 1 h of exposure.The fumigant effects of essential oil from Cinnamomum camphora, P. nigrum and S.japonica were observed on development of (adult and larvae) saw-toothed beetle.Steona japonica showed maximum fumigation effects on adults (46.53%) and larvae(32.31%) at 40 days. The minimum fumigation observed from C. camphora (27.58%)against adult and against larvae (38.95%) at 40 days.The fumigant effects of essential oils from A.ascalonicum and M. haplocalyx were examined against (adults and larvae) maize weevil. M. haplocalyx toxicity to adults(37.34%) was higher than A. ascalonicum toxicity to adults (26.35%), whereas A.ascalonicum toxicity to grubs (50.29%) was higher than M. haplocalyx toxicity to grubs(46.36%) at 16 h of exposure.4. The effects of plant essential oils against house hold pestsThe repellency of essential oils from C. longa and L. cubeba were examined against Monomorium pharaonis. C. longa repelled > 80% ants, whereas L. cubeba repelled >70%, with and without the availability of food up to 4 h of exposure.The repellency of essential oils from P. nigrum was examined against Blattella germanica.P. nigrum showed maximum repellencies against the adult and nymph before (73.33%and 53.33%) and after food (63.33% and 45.00%) in the laboratory at 1h of exposure,it showed maximum repellency at 6 h (65.19%) and 12 h (55.00%) in kitchen.Our study has shown that many plant derivatives possess bioactivities against insect and mite pests of greenhouses, grain stores, and human habitations. They reduce pest infestation,making them important components for Integrated Pest Management (IPM)programs. Future field research is recommended to check their bioactivity against other pests, as well as to observe their effects on beneficial organisms such as pollinators and natural predators of pests. |
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