Plant Protectants Research Articles

Trials of Alternative Codling Moth (Cydia pomonella) Control Strategies in Austria

The control of the codling moth (Cydia pomonella) is becoming very difficult due to the increasing resistance of the pest, the change in climatic conditions, and the loss of plant protectant products for its efficient control. Trials of alternative control strategies against this moth were carried out in Austria in 2007. The efficacy of the four mainly used insecticides was tested according to EPPO standards. The total infestation rate reached 75% in the untreated control. All treatments obtained efficacy rates up to 64%. The results showed that more effective management strategies still have to be developed to sufficiently control the codling moth, especially in integrated production.

Effects of cultivar and agrobotanical storage treatment on organolepetic quality of yam (<i>Dioscorea rotundata</i>)

There is current interest in the search and use of agrobotanicals in preference to conventional chemicals in agriculture as plant protectants hence the need to investigate the potential effects of some of the agrobotanicals on yam food after storage. This study was, therefore, conducted to assess the effects of yam cultivar and agrobotanical extracts on the organoleptic quality and acceptability of two yam based food forms: boiled yam and pounded yam. Tubers of four yam cultivars (Nwaopoko,Danacha, Ezakwukpolo and Pepa) were treated with aqueous leaf extracts of Neem (Azadiracta indica), Scent leaf (Occimum gratissimum), pod extracts of ‘Uda’ (Xylopia aethiopica), root extracts of Ginger (Zingibger officinale) and a synthetic phytohomorne (Gibberellic acid) and stored for six months. Thereafter, two food forms (boiled yam and pounded yam) were prepared from the stored yam tubers and a nine-member panel of judges enlisted to perform sensory quality assessment on them. The attributes scored with respect to boiled yam were colour, taste, texture, mealiness and general acceptability while pounded yam was assessed for its aroma, texture, colour and general acceptability. No significant differences were found among the sensory attributes due to the agrobotanical treatments rather, differences were due to yam cultivars. The results obtained and confirmed by the scatter plots and multiple linear regression showed that texture and taste contributed much to the general acceptability of boiled yam while aroma and consistency were the major qualities of pounded yam. Consistency of pounded yam was best with Nwaopoko and Danacha cultivars but significantly less so with other cultivars with or without agrobotanical treatment. The agrobotanical treatments did not affect the culinary quality of the stored yam tubers as no evidence of such treatment was noticed in the prepared yam foods. This result suggests that the constituent active ingredients imparted on the tubers during storage by the plant extracts were either water-soluble and heat labile or that their shelf lives were less than six months of the storage period and therefore had no effects on the quality attributes of food yams.

Suicidal poisoning with mercaptodimethur–morphological findings and toxicological analysis

In the western countries, the number of fatal intoxications with plant protecting agents has decreased to some extent due to laws restricting the use of highly toxic pesticides like halogenated hydrocarbons. Nevertheless, in consideration of the easy availability of most plant protectants, the small fraction of such fatalities among suicides and intoxications is astonishing. An 80-year-old woman died of an intoxication with methiocarb (mercaptodimethur), a carbamate type pesticide and as such a reversible inhibitor of the acetylcholinesterase. The case is presented because it is the first explicit report on a fatal poisoning of a human with methiocarb. The methiocarb concentrations detected were 6,100 microg/g in stomach content, 4.0 microg/ml in heart blood, 11 microg/g in kidney, 1.9 microg/ml in urine, 25 microg/g in liver, 2 microg/g in bile and 2.5 microg/g in brain tissue.

Comparison of different medical cases in urinary arsenic speciation by fast HPLC–ICP-MS

The inorganic arsenic species As(III), As(V) and the organic species methylarsonate (MMA(V)), dimethylarsinate (DMA(V)) and arsenobetaine (AsB) were determined in human urine by a fast anion exchange HPLC-ICP-MS method, which was developed for clinical laboratories with high sample throughput. This paper compares typical chromatograms of the arsenic species in urine samples collected in different medical cases, for example, for the non-exposed population, for environmentally (plant protectants) and occupationally (glass manufacture) exposed persons, for a person after a failed suicide attempt with As2O3 and for persons before and after administration of the antidot sodium 2,3-dimercapto-1-propane-sulfonate (DMPS). Concentration data of the urinary As species for the non-exposed German population (n=82) are compared with the concentrations before and after administration of DMPS (n=37). For the non-exposed group the toxicologically relevant As in urine consists of 81% DMA(V), 10% MMA(V) and 9% inorganic As. However, a few hours after an acute intoxication with inorganic As this distribution changes dramatically and As(III) and As(V) are predominantly found in urine. After treatment with DMPS the total As concentration increases significantly and mainly MMA(V) and As(III) were found in urine samples.

Jatropha Curcas L., A Multipurpose Stress Resistant Plant with a Potential for Ethnomedicine and Renewable Energy

Jatropha curcas is a stress--resistant perennial plant growing on marginal soils. This plant is widespread throughout arid and semiarid tropical regions of the world and has been used as a traditional folk medicine in many countries. J.curcas is a source of several secondary metabolites of medicinal importance. The leaf, fruits, latex and bark contain glycosides, tannins, phytosterols, flavonoids and steroidal sapogenins that exhibit wide ranging medicinal properties. The plant products exhibit anti-bacterial and anti-fungal activities. The paper highlights the ability of various metabolites present in the plant to act as therapeutic agents and plant protectants. The plant is designated as an energy plant and use of J.curcas oil as biodiesel is a promising and commercially viable alternative to diesel oil. The seeds of the plant are not only a source of biodiesel but also contain several metabolites of pharmaceutical importance. Commercial exploitation for biopharmaceuticals and bio-energy production are some of the prospective future potential of this plant. Further reclamation of wastelands and dry lands is also possible with J.curcas cultivation.

진균 세포벽 유래 신물질을 이용한 감자의 전신적 획득저항성 유도

It was investigated that systemic acquired resistance (SAR) was induced in plant treated with a elicitor, which was derived from a non-virulent fungus. The elicitor, a hyphal cell wall component derived from fungus, induced a production of phytoalexin and a generation of reactive oxygen species (ROS) in potato treated with its low level concentrations. The effect of the fungus-derived elicitor was better than that of virulent pathogen-derived elicitor, which was well known in potato. These results, therefore, suggested potentcial use of fungus-derived elicitor as a new plant protector for commercial development.

Toxicity and feeding deterrence of crude toxin extracts of Lecanicillium (Verticillium) lecanii (Hyphomycetes) against sweet potato whitefly, Bemisia tabaci (Homoptera: Aleyrodidae)

Crude toxins [toxin(V3450) and toxin(Vp28,) extracted from Lecanicillium (Verticillium) lecanii (Zimmermann) Gams & Zare strain V3450 and Vp28 respectively] were tested for contact toxicity, feeding deterrence and repellent activity against the sweet potato whitefly, Bemisia tabaci (Gennadius) (Homoptera: Aleyrodidae). Both toxins showed ovicidal activity to eggs, with LC(50) values of 447 and 629 mg L(-1) respectively. Nymphs of B. tabaci were the most susceptible stages (LC(50) values were calculated at 111 mg L(-1) for toxin(V3450) and 216 mg L(-1) for toxin(Vp28)), and adults were the second most susceptible stages (48 h LC(50) values were calculated at 178 mg L(-1) for toxin(V3450) and 438 mg L(-1) for toxin(Vp28)). Applied to seedlings at a concentration of 400 mg L(-1), the toxins significantly (P < 0.001) reduced the hatching of whitefly eggs and the subsequent survival rate of the nymphs, and the emergence and fecundity of the progeny adults. Both toxins exhibited repellent activity at low concentration (100 mg L(-1)), with repellency index (RI) values of 0.645 for toxin(V3450) and 0.642 for toxin(Vp28), and antifeedant activity at high concentration (1000 mg L(-1)) to adults, with antifeedant index (AFI) values of 0.713 for toxin(V3450) and 0.749 for toxin(Vp28). The results of the present study demonstrate the toxicity, repellence and antifeedant properties of the fungi metabolite toxins on B. tabaci, which might develop as environmentally friendly plant protectant(s).

Gene Cluster Responsible for Validamycin Biosynthesis in Streptomyces hygroscopicus subsp. jinggangensis 5008

A gene cluster responsible for the biosynthesis of validamycin, an aminocyclitol antibiotic widely used as a control agent for sheath blight disease of rice plants, was identified from Streptomyces hygroscopicus subsp. jinggangensis 5008 using heterologous probe acbC, a gene involved in the cyclization of D-sedoheptulose 7-phosphate to 2-epi-5-epi-valiolone of the acarbose biosynthetic gene cluster originated from Actinoplanes sp. strain SE50/110. Deletion of a 30-kb DNA fragment from this cluster in the chromosome resulted in loss of validamycin production, confirming a direct involvement of the gene cluster in the biosynthesis of this important plant protectant. A sequenced 6-kb fragment contained valA (an acbC homologue encoding a putative cyclase) as well as two additional complete open reading frames (valB and valC, encoding a putative adenyltransferase and a kinase, respectively), which are organized as an operon. The function of ValA was genetically demonstrated to be essential for validamycin production and biochemically shown to be responsible specifically for the cyclization of D-sedoheptulose 7-phosphate to 2-epi-5-epi-valiolone in vitro using the ValA protein heterologously overexpressed in E. coli. The information obtained should pave the way for further detailed analysis of the complete biosynthetic pathway, which would lead to a complete understanding of validamycin biosynthesis.

Plant Materials Used for Controlling Insect Pests of Stored Products in Nigeria, Families Annonaceae, Piperaceae, and Rutaceae

ABSTRACT Plant material from the families Annonaceae, Piperaceae, and Rutaceae are used for the protection of stored products against insect pests in Nigeria. Following an outline of the different methods used for assessing insecticidal activity, 16 plants and plant products are alphabetically listed within families, summarizing the laboratory data currently available and, where possible, information on constituents and comparative studies with conventional synthetic insecticides. Of these families, only a few, all species in the genera Citrus, Dennettia, and Piper have been sufficiently tested in the laboratory to give an indication of their potential usefulness as stored-product protectants. More rigorous testing of these plant materials is required if the potential for botanical protectants is to be realized and the plant materials can be compared with recommended synthetic insecticide pyrethroids for repellency/antifeedant activity, contact adult mortality, and reduction in F1 production along with seed viability and land quality. Also extensive surveys to identify more plants with probable insecticidal properties need to be done with standardized assessment of residual effectiveness against all stages of the insect life cycle and the stored commodities. More attention may need to be given to the characterization and quantification of chemical constituents and to variations which may occur in different karyotypes. Determining the availability of appropriate extraction and application technology if the use of plant protectants is to be for the benefit of research, industry, the Nigerian population, and the economy may be necessary. By summarizing the contributions already made on the use of plant materials for protection of stored products against insect pests in Nigeria, it is hoped that duplication will be avoided.

AGROCHEMICAL DISCOVERY: FINDING NEW FUNGICIDES FROM NATURAL PRODUCTS

AGROCHEMICAL DISCOVERY: FINDING NEW FUNGICIDES FROM NATURAL PRODUCTS

Indolizidine and Quinolizidine Alkaloids: Structure and Bioactivity

Abstract A review of the structural identification and bioactivity of simple indolizidine and quinolizidine alkaloids isolated from amphibians, ants,fungi, plants and marine sources, covering the period from 1994 to 1999,is herein presented. Some of the new alkaloids do not have complete structural assignments due to the minute amounts that were isolated and the proposed structures rely on GC-MS and GC-FTIR analyses. Some previously known structures were corrected and others now have complete spectral assignments. The configurational and conformational analysis of new alkaloids is discussed and the alkaloids whose structures were established by X-ray analysis are also presented. Indolizidine and quinolizidine alkaloids from amphibians and ants have been described as noxious compounds and are believed to play an important role in the self defence system of these animals. Their biological activity is likely to arise from interference with ion channels in nerve and muscles cells. Polyhydroxylated indolizidines form an important group of bioactive alkaloids. Different structures are referred as potent inhibitors of glycosidases, as immunosuppressants, as anticancer agents and others are described as anti-HIV agents. Lupine alkaloids (quinolizidine alkaloids from Lupinus species) are associated with plant ecological equilibrium because they are important protectors of plants against herbivores, microorganisms and competing species. They are responsible for the toxic and teratogenic effects observed in livestock and theiraction can be associated with their affinity for nicotinic and muscarinic receptors. Important bioactivity of specific alkaloids is outlined.

Effect of growth regulators on growth, yield and storage life of Kharif onion (Allium cepa)

A field investigation involving pre-harvest sprays of different growth-regulators such as cycocel, salicylic acid and etheral, and plant protectants like mancozeb, carbendazim and streptocyclin, was carried out during the rainy (kharif) seasons of 201819 and 201920 at Neri, Hamirpur, Himachal Pradesh to study their effect on production and storage of kharif onion (Allium cepa L.) variety Agrifound Dark Red. Application of salicylic acid @ 100 ppm followed by cycocel @ 2,500 ppm significantly enhanced the crop growth, yield and reduced various storage losses, viz. physiological loss in weight, diameter, sprouting and rotting during 90 days storage period.

Seed Coating Technologies and Treatments for Onion: Challenges and Progress

Conventional methods to control the onion maggot or onion fly, Delia antiqua (Meigen), have relied on in-furrow applications of the toxicant pesticide, chlorpyrifos. The objective of this research was to develop an onion (Allium cepa L.) seed treatment that utilizes a new chemistry compound that is environmentally safe. Cyromazine is an insect growth regulator with a mode of action different from traditional pesticides used to control onion maggot. Cyromazine has low mammalian toxicity and is relatively nontoxic to other insects, including beneficials. High seed loading rates (50 g·kg-1 active ingredient) are required for optimal efficacy, and conventional slurry methods are inadequate to apply these high loading rates. Film coating and pelleting were performed at Cornell Univ. to apply cyromazine and a registered fungicide (a formulation of thiram and carboxin) to onion seeds. Results of field studies performed over several years revealed that stand losses due to the onion maggot ranged from ≈20% to 60%. Cyromazine applied by either film coating or pelleting decreased the loss by onion maggot from 1% to 8%, and efficacy was comparable to an in-furrow application of chlorpyrifos. Cyromazine was registered as a seed treatment and is commercially used in the northeastern and midwestern United States, where onion maggot is a serious pest. Field emergence was not negatively affected by cyromazine coated onto the seeds when onion seeds are sown in organic (muck) soils. There is other evidence, however, that cyromazine seed treatments may cause phytotoxicity to germination and seedling growth. Testing seed quality in sand or on roll towels revealed a high percentage of abnormal seedlings. Retarded root growth was observed in seeds treated with cyromazine, resulting in an increase in abnormal seedling classifications. A finely ground sphagnum peatmoss applied over the seeds in a roll towel test ameliorated the abnormal root growth symptoms, and seedlings had robust growth. Collectively, film coating and pelleting were effective delivery systems for the application of plant protectants required at time of sowing. Modification of the standard germination test was needed to accurately assess onion seed quality. Moreover, this project was successful due to a team effort of a university seed scientist and entomologists working with onion growers and industry. Future registrations on small acreage, high-value horticultural crops are envisioned to require similar multi-partner approaches. Chemical name used: N-cyclopropyl-1,3,5-triazine-2,4,6-triamine (cyromazine).

Potential of microbore HPLC within a multiresidue method for the trace analysis of plant-protective substances in water.

The performance of microbore HPLC as a "measurement channel" within a true multiclass/multiresidue method for monitoring plant protectants in raw and potable water is demonstrated. The method has a modular design and consists of a non-selective sampling and preparation line generating 250 microL of an "extract" from a 100-mL water sample; this extract can be introduced to up to four measurement channels, as required by the analytical task. The microbore HPLC channel can be used to quantify 34 plant protectants in the 0.1 microg L(-1) concentration range by use of diode-array detection at seven different wavelengths. A solvent change is necessary to link sample preparation to microbore HPLC; this uses 50 microL of the "extract" and is accomplished directly in an autosampler vial. Performance characteristics were evaluated for tap water spiked at 0.2 microg L(-1). Average recoveries were between 65 and 100% and method detection limits were 0.07 microg L(-1) or better. The ability to provide comparable and accurate results was proven by participation in an interlaboratory comparison trial. The procedure for preparing microbore columns from 750 microm i.d. PEEK tubing is described in detail to enable the reader to prepare his own columns. The reproducibility of this preparation procedure was proven by an analysis-of-variance test.

The algal polysaccharide carrageenans can act as an elicitor of plant defence.

• Effects of two algal polysaccharides, laminarin and carrageenans, on defence responses and signalling in tobacco plants is presented. A possible role as defence elicitors is important in the context of the use of algal extracts as plant protectants. • The effect of the extracts was assessed after infiltration of tobacco leaves, and compared to the effect of a known elicitor of Phytophthora parasitica var. nicotianae(Ppn). • Of the two algal polysaccharides, only carrageenans efficiently induced signalling and defence gene expression in tobacco leaves, as observed with Ppn elicitor. λ-carrageenan, with its high sulphate content, proved the most active. Defence genes encoding sesquiterpene cylase, chitinase and proteinase inhibitor were induced locally, and the signalling pathways mediated by ethylene, jasmonic acid and salicylic acid, were triggered. Some effects lasted for at least a week. • λ-Carrageenan can elicit an array of plant defence responses, possibly through an effect of its high sulphate content. This helps clarify the mechanism of plant protection by algal extracts.

Rapid Target Analysis for Pesticides in Water by Online Coated Capillary Microextraction Combined with Liquid Chromatography and Tandem Mass Spectrometry

The applicability of online trace enrichment with custom-made coated capillaries combined with tandem mass spectrometry was demonstrated for the target analysis of selected pesticides (mainly herbicides, e.g., triazines, phenylureas, and acetanilides) in water. The developed method allows rapid determination of several widely used plant protectants within a total analysis time of 11 min. Good linearity (r > or = 0.995) was obtained for the selected pesticides in the range of 0.050-50 microg/L. The relative standard deviations (RSDs) of the peak areas were < or = 3.8% for spiked Milli-Q water (5 microg/L). The RSDs obtained in analyses of spiked (1 microg/L) water samples (brook water, river water, sewage plant effluent) ranged from 2.9 to 6.8%, indicating low influence of the matrix on enrichment and detection. The detection limits, which ranged from 10 to 90 ng/L, fulfilled the requirements of the European regulations for drinking water. The polyacrylate coating of the extraction capillary showed good stability in the presence of water and acetonitrile and allowed > or = 100 extractions with 1 capillary.

Biorational and Conventional Plant Protectants Reduce Feeding by Adult Japanese Beetles

Abstract Nine commercial plant protectants were tested for efficacy against feeding by adult Japanese beetles (Popillia japonica Newman). Treatments included an endotoxin from a bacterium [Bacillus thuringiensis (Berl.) var. san diego]; microencapsulated pyrethrum extracted from pyrethrum [Tanacetum cinnerariifolium (Trev.) Schultz-Bip.], two extracts from neem (Azadirachta indica A. Juss); an extract from cayenne pepper (Capsicum annuum L. var. annuum Longum Group); an extract from garlic (Allium sativum L.); rotenone extracted from galedupa (Derris trifoliata Lour.) and barbasco [Lonchocarpus sericeus (Poiret) Kunth] or timbo (L. nicou Aublet D.C.); carbaryl (1-napthyl methylcarbamate); and the pyrethroid, fenpropathrin. Experimental plots were located at the Horticulture Field Laboratory (HFL), Raleigh, and the Mountain Horticultural Crops Research and Extension Center (MHCREC), Fletcher, NC. Himalayan birches [Betula utilis var. jacquemontii (Spach) Winkl.] were used as host plants. Treatments were applied twice, 2 weeks apart. Five weeks after initial application, trees treated with fenpropathrin averaged 2% defoliation vs. 40% defoliation for the control trees at HFL; and 3% defoliation vs. 100% defoliation for the control trees at MHCREC. Rotenone treatments averaged 10% defoliation at HFL and 92% defoliation at MHCREC. The following treatments were not significantly different from the control at week 5 at either location: garlic extract, neem extracts, cayenne pepper extract, microencapsulated pyrethrum, encapsulated bacterial endotoxin, and carbaryl.

Determination of Regularly Distributed Plant Protectants in Raw and Drinking Waters, Using a Multiresidue Method with Cyclodextrin-Modified Micellar Electrokinetic Chromatography

Eighteen plant protectant compounds were separated and determined by cyclodextrin-modified micellar electrokinetic chromatography (MEKC) in a multiclass/multiresidue method. The pesticides included are those dispersed in the greatest amounts today over agricultural acreage, and they represent 8 different classes of compounds (azoles, benzoic acids, chloroacetanilides, phenoxy acids, phenylureas, sulfonylureas, thiocarbamates, and triazines) covering a wide range of chemical reactivities and physicochemical properties. A 500 mL sample of tap water is preconcentrated by solid-phase extraction (SPE) with 300 mg combined polystyrene-divinylbenzene and methacrylate macroporous resins. Trapped analytes are eluted collectively with diethyl ether. Concentration and solvent change yield 250 microL of an acetone "concentrate," which is further worked up and concentrated 1:10 to produce the MEKC injection solution containing 10 mmol/L sodium dodecyl sulfate (SDS) surfactant. For MEKC, 2 phosphate/SDS buffer systems were designed, each allowing complete separation of all pesticides in a single run. Sensitivity was enhanced by a self-etched bubble cell and an injection procedure which employs stacking at reversed polarity. The ability of MEKC to determine plant protectants in raw and drinking waters at the 0.1 microgram/L level, as demanded by the guidelines of the European Union, was demonstrated with spiked tap waters. Recoveries were between 75 and 110%, and limits of quantification, evaluated as method detection limits according to guidelines of the U.S. Environmental Protection Agency, ranged between 0.03 and 0.10 microgram/L. The precisions of the relative migration times were all below 0.5%.

A multiresidue method with mobile on-site sampling based on SPE for ultratrace analysis of plant protectants in environmental waters

A new multiclass/multiresidue method for monitoring plant protectant residues in raw- and drinking waters with on-site sampling using a mobile, self-contained sampling unit based on SPE was developed and validated. 38 active compounds with widely varying chemical and physicochemical properties (acid-base properties, polarities, vapor pressures, solubilities) are measured from just one sample and work-up. 100 mL water, acidified with acetic acid, are drawn through a cartridge filled with Amberchrom resins by means of a calibrated 100 mL syringe driven by servo motors, control circuit and rechargeable battery. Volumetric flow is high, quantitative extraction of acidic, neutral and weak basic substances is accomplished in a few minutes and loaded cartridges are transported into the laboratory. Further work-up, i.e. elution, drying, concentration and solvent change, is designed strictly non-selectively and produces 250 μL of an “extract”, which is the starting point of two GC measurement lines, GC-NPD and GC-ECD. Chlorinated herbicide acids are derivatised into perfluorinated benzyl esters employing reaction conditions so smooth that the organochlorine hydrocarbons are not destroyed at all and both substance classes can be chromatographed in one GC run. ECD-chromatograms from derivatised solutions are rather complex, therefore the flow is split after injection onto two columns with different polarities and two EC-detectors in order to resolve all analytes and matrix interferents. Short-chain carbonic acids added to the water prior to preconcentration are adsorbed on the hydrophobic surface in a reversible process and impart the Amberchrom resins with a partially hydrophilic character. Method performance was ascertained using tap water fortified at the 0.2 μg L–1 level: Mean recoveries were between 70 and 115% and method detection limits (MDLs) below 0.08 μg L–1. Waters from different sources did not affect the recoveries, loaded cartridges are stable for two weeks’ storage when cooled.

Antifeedant activity of citrus limonoids against Colorado potato beetle: comparison of aglycones and glucosides

The importance of plant allelochemicals in plantherbivore interactions is well known. Although some of these phytochemicals act as phagostimulants for specific herbivores, the majority of allelochemicals examined appear to function primarily in plant defense, acting as insect antifeedants, growth regulators, and/or toxins (Jermy, 1966; Bernays & Chapman, 1977). As such, these chemicals have great potential for use in pest management, either directly, as natural plant protectants, or as models for the development of synthetic products. Citrus limonoids, a group of terpenoid allelochemicals found in the plant family Rutaceae have previously been shown to act as insect antifeedants (Klocke & Kubo, 1982; Alford et al., 1987; Mendel et al., 1991) as well as mammalian anticarcinogens (Lam & Hasegawa, 1989; Miller et al., 1989). They are also useful as chemotaxonomic markers (Hasegawa & Miyake, 1996). Thus, citrus limonoids are important functional chemicals in agriculture and medicine. Limonoid aglycones, which are present in young and growing citrus tissues, are converted to their respective 17β-D-glucoside derivatives during late stages of fruit growth and maturation (Hasegawa et al., 1991; Fong et al., 1992). Limonoid glucosides, such as limonin 17β-D-glucopyranoside, are accumulated in mature fruit tissues and seeds as major secondary metabolites (Fong et al., 1989; Hasegawa et al., 1991). Thirty-six limonoid aglycones and 17 limonoid glucosides have been isolated from Citrus and its hybrids, yet few have been investigated for their biological activities. None of the limonoid glucosides have previously been examined for antifeedant activity against insects. In this study we compared the antifeedant activity of limonoid aglycones and glucosides against Colorado potato beetle, Leptinotarsa decemlineata (Say), larvae.