ENTOMOLOGY
F. Mansour et al. (2004) Phytoparasitica 32(1):66-72
The Potential of Middle Eastern Flora as a Source of New Safe Bio-Acaricides to Control Tetranychuscinnabarinus, the Carmine Spider Mite
F. Mansour, 1 H. Azaizeh, *'2 B. Saad, 3 Y. Tadmor, 4 F. Abo-Moch 1 and O. Said 2 Twenty-nine plant extracts of local species were evaluated for their potential as a source of bioactive ingredients with significant acaricidal activity that could lead to the development of new and safe bio-acaricides. The crude extracts (70% ethanol) of these plants were tested for their acaricidal activity against the carmine spider mite Tetranychus cinnabarinus in a bioassay under controlled conditions. Mortality, repellency, and the number of eggs laid were measured. Extracts from Eucalyptus camaldulensis and Inula viscosa caused more than 25% mortality. Sixteen plant extracts showed significant repellency compared with the control. The six best extracts, resulting in more than 75% repellency, were from Allium
sativum, Capparis spinosa, Cupressus sempervirens, Lupinus pilosus, Rhus coriaria and Tamarix aphylla. Extracts from 16 plants were found to cause a significant reduction in the number of eggs laid compared with the control. The greatest reduction was achieved by extracts from C. spinosa, Cyperus rotundus, E. camaldulensis, L pilosus, Punica granatum, R. coriaria and T. aphyUa. A relatively negative fit was found between the mean number of repelled mites and the number of eggs laid (r=-0.65), which might indicate that most repelled mites were unable to lay eggs before leaving the leaf discs of the bioassay. Our results show that several plant extracts have good potential for acaricidal activity and are worth further investigation. KEY WORDS: Tetranychus cinnabarinus; plant mites; botanical pesticides; repellency; reduction of fecundity, INTRODUCTION While pesticides have done much to improve yields of high-quality agricultural products, the long-term use of chemical pesticides has harmful effects on human beings, beneficial organisms, and the environment. Biologically based technologies, such as biological control, are attractive because they can provide lasting, highly selective and effective pest control (4,20). In this light, the growing need to develop pesticides that are not harmful to people and the environment has gradually heightened interest in biopesticides. This awareness has led to a steadily increasing movement towards a more environmentoriented, sustainable agriculture with low or no input of toxic synthetic pesticides and other Received July 24, 2003; accepted Sept. 22, 2003; http:llwww.phytoparasitica.orgposting Dec. 16, 2003. 1Dept. of Entomology,ARO, Newe Ya'ar Research Center, Ramat Yishay 30095, Israel. 2The Galilee Society, R&D Regional Center (affiliated with Haifa University), Shefa-Amr 20200, Israel. *Corresponding author [e-mail:
[email protected]]. 3Dept. of Allied Medical Sciences, The Arab American University, Jenin (AAUJ), Palestinian Authority. 4Inst. of Vegetable and Field Crops, ARO, Newe Ya'ar Research Center, Ramat Yishay 30095, Israel.
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agricultural chemicals, in an attempt to preserve and protect the environment as well as human health (20). Therefore, considerable efforts are being made worldwide to find safer, biodegradable and environmentally friendly substitutes for synthetic pesticides. Two common arthropod pests of cosmopolitan importance are the tetranychid mites: Tetranychus urticae Koch and T. cinnabarinus Boisd. These mites feed on numerous cultivated crops and cause serious damage, reducing quality and quantity of yield all over the world, leading to reduction or total loss of yield (7,19). The economic importance of these mites is constantly increasing, because of the development of resistance and resurgence of their populations due to the non-selectivity of synthetic pesticides, which damage and may even destroy natural enemies, such as predaceous mites, and predatory spiders. The carmine spider mite T. cinnabarinus may be a host race (6) or perhaps a synonym (5) of the two-spotted spider mite, T. urticae, although some authorities consider it and several other closely similar spider mites as separate species (3). Whatever its taxonomic status, we shall call the spider mite found in the Middle East - T. cinnabarinus - the carmine spider mite (CSM), and T. urticae- the two-spotted spider mite (TSM). The use of selective pesticides is suggested as the first step in developing an integrated mite management strategy. Therefore, employing botanical pesticides that are relatively harmless to natural enemies could increase the effectiveness of natural predation. This may in turn enable fewer pesticide applications, and reduce production costs and environmental pollution. Therefore, during the last 30 years many plant products have been tested as botanical pesticides to control spider mites (12). For example, essential oils were extracted from 14 Labiatae plant species and some of them caused mortality, induced repellency and reduced egg-laying in adult females of the CSM (12). Different commercial formulations of neem (Azadirachta indica) were obtained from the seeds of the neem tree and found to be as effective as botanical pesticides against the TSM on different crops where these compounds showed ovipositional deterrence, suppressed the emergence of nymphs and caused reduction in leaf damage (10,17). Some of the formulations from neem were effective against mites and the level of protection was comparable to that of synthetic acaricides. However, some of the neem formulations at some concentrations caused mite resurgence (9). The botanical insecticide bionim, based on a neem extract, was registered in Sweden in 1997 for use against pests, including the TSM, in ornamental plants. Among the bioactive materials is azadirachtin, a mixture of several structurally related tetranotriterpenoids isolated from the seeds of the neem tree (16). The pesticidal activity of extracts of two Eucalyptus plant species (red and spotted gum) in comparison with some biocides and conventional pesticides was evaluated against TSM and Bemisia tabaci infesting cotton fields in Egypt and showed very promising acaricidal activity for both insects (13). Because many botanical pesticides are considered to be safe compounds, the essential oils are attractive chemicals for the control of Varroa mites on honeybees because they are perceived as 'natural' compounds that will not contaminate hive products (15). The hills and mountains of the eastern Mediterranean region are covered with over 2600 plant species of which more than 700 are noted for their uses as medicinal herbs or as botanical pesticides (1,2,12,14). The aim of our current work is to evaluate the potential of plant extracts of some of these local species grown in the Galilee region of Israel as a source of bioactive ingredients with significant acaricidal activity that could lead to the development of new bio-safe products for the benefit of sustainable agriculture in the region. Phytoparasitica 32:1, 2004
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MATERIALS AND METHODS
Plant extracts
In order to study in detail the potential of local plant species as botanical pesticides, 29 plant species (Table I) were chosen for this study based on an ethnopharmacological survey and old literature (l,i). Plant species used were identified based on their RDC herbarium voucher number (14). For each species, specimens were collected from several plants grown naturally on the mountains of the Galilee region of Israel. Plant extracts were prepared from a representative sample of 10 g fresh plant material homogenized in 100 ml of 70% methanol and placed on a shaker at 100 rpm for 48 h at room temperature. The mixture was filtered using a fiber-glass filter to remove all plant debris. The filtrate was kept in a refrigerator at 5~ until use in the bioassay.
Maintenance of the carmine spider mite T. cinnabarinus The local strain of T. cinnabarinus used in this study originated from infested leaves of cotton which had not been sprayed with pesticides. The mite stocks were grown under controlled conditions in a controlled climate room at 25+2~ 60+ 5% r.h., with 16 h light supplied by a series of fluorescent lamps, yielding a light intensity of ,-,2000 lux. Rearing was done on 23-week-old kidney bean (Phaseolus vulgaris) as described elsewhere (18). Briefly, bean plants were grown in 25x32x8-cm-high pots filled with peatmoss and vermiculite (2:1) and maintained in a growth chamber under controlled conditions (26i2~ 60~5% r.h. and 16 h light). Mites were transferred from aging plants to younger ones by placing old leaves infected with mites near 7- to 10-day-old healthy seedlings. Individual female mites were collected and transferred for bioassay tests using a fine hairbrush.
The bioassay for testing plant extracts
To investigate the effect of active fractions or isolated compounds from promising plants on spider mites, we used a bioassay described previously (11). Briefly, 54-mm-diam bean leaf discs taken from ,-~2-week-old plants (grown as described above) were dipped for 5 sec in the tested extract solution, placed bottom side up on a filter paper in a tray, and air-dried at room temperature before being tested. In parallel, comparable control discs were prepared and dipped in the extraction solution only. Each filter paper with the leaf disk was placed on a sheet of plastic foam, floating on water in a petri dish (90 mm diam). After drying, 20 adult female mites (~5 days old) were placed on each leaf disc in triplicates per treatment. The treated mites were incubated under controlled conditions as described above. Numbers of live, dead or repelled mites (those which had left the leaf disks were considered as repelled) and fecundity (calculated on the basis of eggs per treatment) were determined after 48 h of incubation.
Statistical analysis
The experiment had a completely randomized design with three replicates per treatment. The ranking of means was done utilizing the Tukey Kramer's test (P_ 0
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TABLE 2. Effects of different plant extracts on the mortality, repelled status, and fecundity of the carmine spider mite (mean values [of three replicates] after 48 h of incubation) Extract Treatment no. (plant species)
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17
Alhagimaurorum Alliumsativum Asphodelus microcarpus Beta vulgaris Capparisspinosa Citrulluscolocynthis Cupressus sempervirens Cyperusrotundus Ecbaliumelaterium Eryngiumcreticum Eucalyptus camaldulensis Euphorbia hierosolymitana lnula viscosa Laurusnobilis Lupinuspilosus Majoranasyriaca Matricariaaurea Melia azadirachta Menthapiperita Myrtus communis Petroselinumsativum Pinushalepensis Prosopisfarcta Punicagranatum Rhus coriaria Ruta chalepensis Salviafruticosa Tamarixaphylla Varthemiaiphionoides
Mites
No. of Eggs
No. of Eggs/(by live + repelled)
Live 11.0 bcdef 2.3 ij 9.7 cdefgh
Dead 0.3 bc 0.3 bc 1.7 bc
Repelled 9.0 cdefgh 17.3 ab 8.7 defghi
188 abcd 50 efg 113 bcdefg
9.4 abc 2.5 def 6.2 bcdef
11.7 bcdef 2.3 ij 10.7 bcdef 2.3 ij
1.7 bc 0.0 c 2.7 bc 1.0 bc
6.7 efghijk 17.7 a 6.7 efghijk 16.7 ab
194 abcd 13 g 94 defg 30 efg
10.6 abc 0.7 f 5.3 cdef 1.6 def
2,3 ij 9,0 defgh 8,7 defgh
3.7 abc 4.3 abc 0,3 bc
18.7 g 106 defg 145 abcdef
1.1 ef 6.5 bcdef 7.3 abcd
7.3 efghi
9.3 a
14.0 abcd 6,7 efghijk 11.0 bcdefg 3,3 hijk
21 g
1.8 def
7.0 efghij
0.3 bc
12.7 abcde
117 bcdefg
5.9 bcdef
7.3 efghi 6.3 ab 6.3 efghijk 94 defg 13.7 abcd 1.7 bc 4.7 ghijk 202 abcd 1.0j 1.7 bc 17.3 ab 15 g 12.7 abcde 5.0 abc 2.3 ijk 100 defg 10.3 cdefg 3.3 abc 6.3 efghijk 227 ab 18 9.7 cdefgh 1.0 bc 9.3 cdefgh 107 cdefg 19 10.7 bcdef 4.7 abc 4.7 ghijk 99 defg 20 13.7 abcd 2.3 bc 4.0 hijk 186 abcd 21 15.3 abc 0.7 bc 4.0 hijk 226 abc 22 14.3 abcd 5.0 abc 0.7 k 147 abcde 23 10.7 bcdef 1.3 bc 8.0 defghij 114 bcdefg 24 4.3 ghij 4.0 abc I 1.7 abcdef 18.3 g 25 1.0j 3.0 bc 16.0 ab 22 g 26 5.7 fghij 1.7 bc 12.7 abcde 54 efg 27 3.7 hij 2.7 bc 13.7 abcd 27 fg 28 2.0 ij 2.7 bc 15.3 abc 16 g 29 16.7 ab 1.7 bc 1.7 jk 210 abcd 30 Control 17.2 a 1.0 c 1.8 k 247 a Within columns, values followed by a common letter do not differ significantly (P
