Correlation of phenolic acid content of maize to resistance toSitophilus zeamais,the maize weevil,in CIMMYT'S collections

The (E)-ferulic acid content of the grain of nine populations of land races of maize derived from CIMMYT's collections was found to be negatively correlated to susceptibility characteristics towards the maize weevilSitophilus zeamais. Correlation coefficients for six susceptibility parameters and (E)-ferulic acid content were significant and ranged from –0.58 to –0.79. A multiple regression analysis by the SAS forward procedure using the primary seed characteristics associated with susceptibility indicated that the ferulic acid content was the only significant factor in explaining variation in at least two susceptibility parameters: the Dobie index and adult preference. In 15 CIMMYT pools, correlations between four susceptibility parameters and (E)-ferulic acid content were also significant (–0.76 to –0.81). The results suggest that phenolic acid content is a leading indicator of grain resistance or susceptibility to insects and may represent a newly identified mechanism of resistance.     

Determination of chirality in 5-hydroxy-4-methyl-3-heptanone,the aggregation pheromone ofSitophilus oryzae (L.) andS. zeamais Motschulsky

The chirality of the pheromone of the rice weevil,Sitophilus oryzae (L.), and the maize weevil,S. zeamais (Motschulsky), 5-hydroxy-4-methyl-3-heptanone, was determined using an acetyl lactate derivatization procedure. Maize weevils were shown to produce >98% 4S,5R. Determination was more difficult with rice weevils due to a smaller quantity of insect extract, but they were shown to produce at least 92% 4S, 5R.The attractancy of the four synthetic stereoisomers of 5-hydroxy-4-methyl-3-heptanone was tested using rice and maize weevils. As expected, both species were most strongly attracted to the 4S, 5R enantiomer. Maize weevils also showed low but significant responses (P < 0.05) to both 4R, 5R and 4S,5S. Rice weevils showed a highly significant (P < 0.01) response to 4R, 5S, although it was only about one third the response to 4S, 5R. Thus, (4S,5R)-5-hydroxy-4-methyl-3-heptanone is clearly the major component of the pheromone of bothS. zeamais andS. oryzae.This article reports the results of research only. Mention of a proprietary product does not constitute an endorsement or a recommendation for its use by USDA.     

Grain weevil,Sitophilus granarius (L.): Antennal and behavioral responses to male-produced volatiles

Coupled GC-EAG techniques have been applied to the study of volatiles from the grain weevil,Sitophilus granarius. for the first time. The size of EAG response was independent of the sex of the responding insect but was consistently larger to extracts of males than those of females. This difference was reflected in a behavioral preference for the male extracts by mated adults of both sexes tested together and virgin adults of both sexes tested separately. The GC-EAG results provide evidence for two materials that are released specifically by the males. Using circular dichroism. one has been found to be identical stereochemically with the (2S,3R)-sitophilate reported by others as the aggregation pheromone in a different strain. This enhances the prospects for the development of a single pheromone lure that would be generally applicable whatever the origin of the strain. The small amount of sitophilate found in the males suggests that it is not stored in large amounts. The other material, present in such a small amount that it has yet to be fully characterized, elicits a higher antennal activity than sitophilate and may have a significant role to play in enhancing the trap catch of this economically important pest.     

Male-produced aggregation pheromone in pea and bean weevil,Sitona lineatus (L.)

The attraction ofS. lineatus to live baits comprisingS. lineatus feeding onVicia faba (L.) was studied in a field experiment in the early spring. There was clear evidence that maleS. lineatus produced an aggregation pheromone which attracted approximately equal numbers of both sexes from overwintering sites. No evidence was obtained for the production, in the spring, of any semiochemical by female weevils.Coleoptera: Curculionidae.     

Antennal olfactory response of boll weevil to grandlure and vicinal dimethyl analogs

Electroantennogram techniques were used to elucidate antennal olfactory response of male and female boll weevils to a dilution series of grandlure, its components, and some vicinal dimethyl analogs. At higher concentrations, response to the mixture of the two aldehyde components of grandlure was significantly higher than to the two alcohol components. Only one vicinal dimethyl analog elicited a significantly higher response than the control. There were no significant differences in response due to sex over all compounds.Texas Agricultural Experiment Station paper number 16382. Research supported by McIntire-Stennis project 1525. All programs of the Texas Agricultural Experiment Station are available without regard to race, sex, color or religion.     

Aggregation pheromone of the male granary weevil,Sitophilus granarius (L.)

Evidence for a male-produced aggregation pheromone inSitophilus granarius is reported. Hexane extracts of Tenax®-trapped volatiles from males held on wheat were attractive to both sexes in a multiple-choice olfactometer and pitfall bioassay chamber. A quantitative relationship existed between days of insect exposure on disks and degree of responsiveness. The maximum response was to 35 insect-day-equivalents. Diel-related activity showed both sexes responsive during photophase and nonresponsive during scotophase.Coleoptera: Curculionidae.Contribution to Regional Research Project NC151, Marketing and Delivery of Quality Cereals and Oilseeds in Domestic and Foreign Markets.Mention of a commercial or proprietary product does not constitute an endorsement by the USDA.     

Chemosensory responses of cowpea weevil,Callosobruchus chinensis to an aquatic weed,water hyacinth,Eichhornia crassipes (Mart) Solms

The behavioral responses of cowpea weevil,Callosobruchus chinensis to the leaf extracts of the aquatic weed, water hyacinth,Eichhornia crassipes (Mart) Solms. was evaluated by three different methods. The petroleum ether-soluble fraction ofE. crassipes induced high weevil attraction in all methods employed. The olfactometer assay provided a reading on weevil chemosensory responses, whereas the free-choice tests measured response and preference of weevils to the untreated or extract-treated food grain of their choice over a longer period. The extracts were also presented under no choice test conditions to assay them for the presence of oviposition stimulants. In all these methods the extracts of water hyacinth evoked a quick directional response. Another interesting feature is that the extract, besides producing attraction, also caused mortality of the insects.     

Alkanes from surface lipids of sunflower stem weevil,Cylindrocopturus adspersus (LeConte)

The stem weevil,Cylindrocopturus adspersus (LeConte) (Coleoptera: Curculionidae) yields 3% of its body weight as extractable lipids (40 g/ weevil). The alkane fraction was composed ofn-alkanes (38%) and branched alkanes (62%). The compounds were characterized by gas chromatography-mass spectrometry (GC-MS). The chromatogram contained several single-component peaks (9 of 25). Only seven dimethylalkanes were isolated (17.8%): 9,19- and 9,21-dimethylheptacosane; 9,19- and 9,21-dimethylnonacosane; 9,21- and 11,21-dimethylhentriacontane; and 11,21-dimethyltritriacontane. Important methylalkanes were: 2-methyltetra- and hexacosanes and 10-methylhexa- and octacosanes. Late-eluting gas chromatography peaks were composed of simple alkane mixtures or a single component.     

Feeding deterrent compounds to the boll weevil,Anthonomus grandis Boheman in Rose-of-Sharon,Hibiscus syriacus L.

The Rose-of-Sharon,Hibiscus syriacus (L.), can be a significant alternate host plant for the boll weevil,Anthonomus gradis (Boh.). Boll weevils are known to be deterred from feeding and ovipositing in the buds unless the calyx is removed. This investigation was initiated to identify calyx allelochemicals that deter feeding with the eventual strategy of breeding for cotton lines high in these allelochemicals in the appropriate tissues. The feeding deterrency of calyx tissue from the buds of Rose-of-Sharon for the boll weevil was confirmed. The most active deterrent fraction was found to contain mostly fatty acids and their methyl esters. Saturated fatty acids and their methyl esters were generally found to be stimulatory, while the unsaturated species were found to be deterrent. Higher quantities of the fatty acids, particularly the unsaturated species, were found in Rose-of-Sharon calyx tissue than in the buds without calyx. This supports the hypothesis developed through the isolational work and testing of standards that the unsaturated fatty acids are significant deterrents of boll weevil feeding.Coleoptera: Curculionidae.Malvales: Malvaceae.Mention of a commercial or proprietary product in this paper does not constitute endorsement of this product by Delta State University or USDA.     

Cuticular hydrocarbons of adults of the cowpea weevil,Callosobruchus maculatus

The composition of the cuticular hydrocarbons of the cowpea weevil,Callosobruchus maculatus (F.), was determined by using combined gas chromatography-mass spectrometry. The hydrocarbons constituted 88% of the cuticular lipids and were composed of four homologous series of alkanes. Mono- and dimethyl branched-chain alkanes made up 83% of the hydrocarbon fraction.Coleoptera: Bruchidae.Mention of a proprietary product or company name in this paper does not constitute a recommendation of this product by the U.S. Department of Agriculture.     

Components of male aggregation pheromone of strawberry blossom weevil, Anthonomus rubi herbst. (Coleoptera:Curculionidae)

The strawberry blossom weevil, Anthonomus rubi, is a major pest of strawberries in the United Kingdom and continental Europe. As part of a project to develop noninsecticidal control methods, the pheromone system of this species was investigated. Comparison of volatiles produced by field-collected, overwintering individuals of each sex led to identification of three male-specific compounds—(Z)-2-(3,3-dimethylcyclohexylidene)ethanol, (cis)-1-methyl-2-(1-methylethenyl)cyclobutaneethanol, and 2-(1-methylethenyl)5-methyl-4-hexen-1-ol (lavandulol)—in amounts of 6.1, 1.2, and 0.82 g/day/male. The first two compounds are components of the aggregation pheromone of the boll weevil, Anthonomus grandis, grandlure II and grandlure I, respectively. Grandlure I was the (1R,2S)-(+) enantiomer and lavandulol was a single enantiomer, although the absolute configuration was not determined. Trace amounts of the other two grandlure components (Z)-(3,3-dimethylcyclohexylidene)acetaldehyde (grandlure III) and (E)-(3,3-dimethylcyclohexylidene)acetaldehyde (grandlure IV) were also detected. (E,E)-1-(1-Methylethyl)-4-methylene8-methyl-2,7-cyclo-decadiene (germacrene-D), a known volatile from strawberry plants, Fragaria ananassa, was collected in increased amounts in the presence of pheromone-producing weevils. Male weevils only produced pheromone on F. ananassaand not on scented mayweed, Matracaria recutita, or cowparsley, Anthriscus sylvestris, although these are known food sources. In field trials using various combinations of synthetic grandlures I, II, III, and IV and lavandulol, significantly more weevils were caught in traps baited with blends containing grandlure I and II and lavandulol than in those baited with blends without lavandulol or unbaited controls. Addition of grandlure III and IV had no significant effect on attractiveness. Horizontal sticky traps were found to be more effective than vertical sticky traps or standard boll weevil traps. In mid-season females predominated in the catches, but later more males than females were trapped.     

Lack of chemical factors in host-plant resistance of alfalfa towards alfalfa weevil: Ovicidal activity of some coumarin derivatives

A resistant line of alfalfa was studied in an attempt to identify possible chemical factors responsible for alfalfa weevil (Hypera brunneipennis) resistance. Bioassays were developed to measure ovicidal, larval development, pupation, and adult development rates. Serial alfalfa extracts of a weevil-resistant line showed no effect in the bioassays when compared to those of a weevil-susceptible line. It was concluded that resistance substances are not present but that resistant lines are simply more tolerant to weevil attack. Alfalfa constitutents and synthetic analogs were also screened in the egg hatch bioassay. Among these were a series of 3-acyl-4-hydroxycoumarins. 3-Acyl-4-hydroxycoumarins with short-chain acyl groups showed good ovicidal rates, but activity decreased with increasing length of the acyl group.     

Aggregation pheromone for the pepper weevil,Anthonomus eugenii cano (Coleoptera: Curculionidae): Identification and field activity

This study describes the identification of an aggregation pheromone for the pepper weevil,Anthonomus eugenii and field trials of a synthetic pheromone blend. Volatile collections and gas chromatography revealed the presence of six male-specific compounds. These compounds were identified using chromatographic and spectral techniques as: (Z)-2-(3,3-dimethylcyclohexylidene)ethanol, (E)-2-(3,3-dimethylcyclohexylidene)ethanol, (Z)-(3,3-dimethylcyclohexylidene)acetaldehyde, (E)-(3,3-dimethylcyclohexylidene)acetaldehyde, (E)-3,7-dimethyl-2,6-octadienoic acid (geranic acid), and (E)-3,7-dimethyl-2,6-octadien-1-ol (geraniol). The emission rates of these compounds from feeding males were determined to be about: 7.2, 4.8, 0.45, 0.30, 2.0, and 0.30µg/male/day, respectively. Sticky traps baited with a synthetic blend of these compounds captured more pepper weevils (both sexes) than did unbaited control traps or pheromone-baited boll weevil traps. Commercial and laboratory formulations of the synthetic pheromone were both attractive. However, the commercial formulation did not release geranic acid properly, and geranic acid is necessary for full activity. The pheromones of the pepper weevil and the boll weevil are compared. Improvements for increasing trap efficiency and possible uses for the pepper weevil pheromone are discussed. A convenient method for purifying geranic acid is also described.The mention of firm names or trade products does not imply endorsement or recommendation by the U.S. Department of Agriculture over other firms or similar products not mentioned. All programs and services of the U.S. Department of Agriculture are offered on a nondiscriminatory basis without regard to race, color, national origin, religion, sex, age, marital status or handicap.     

Identification and field evaluation of the compounds comprising the sex pheromone of the female boll weevil

The terpenoid compounds (+)-cis-2-isopropenyl-1-methylcyclo-butaneethanol (I), (Z)-3,3-dimethyl-A-cyclohexaneethanol (II), and -caryophyllene were isolated from frass of the female boll weevil (Anthonomus grandis Boheman). In laboratory bioassays, a mixture of these components attracted primarily males, whereas the male pheromone, grandlure, attracted primarily females. The addition to the cotton bud hydrocarbons, -pinene, myrcene, andl-lim-nene, improved the response by males so that the potency of the mixture was comparable to that of grandlure for females. In field tests, I + II + hydrocarbons attracted both sexes, but grandlure alone and grandlure + hydrocarbons were more effective.Coleoptera: Curculionidae.In cooperation with the Mississippi Agricultural and Forestry Experiment Station, Mississippi State, Mississippi 39762.Mention of a commercial or proprietary product in this paper does not constitute endorsement of this product by USDA.     

Effects of mixtures of phenolic acids on phosphorus uptake by cucumber seedlings

To determine how individual phenolic acids in a mixture might affect phosphorus (P) uptake, 15-day-old cucumber seedlings grown in solution culture were treated with ferulic, vanillic,p-coumaric, or equimolar mixtures of these phenolic acids. Phenolic acid and P uptake were determined by solution depletion. The joint action of the mixtures of these phenolic acids on P uptake was primarily additive. Thus, as the number of phenolic acids increased in the mixture, the concentrations of the individual phenolic acids in the mixture required to bring about a given response declined. Seedling uptake of individual phenolic acids from solution mixtures of phenolic acids was reduced when compared to the uptake of phenolic acids from single phenolic acid solutions. The magnitude of the reduction varied with phenolic acid and concentration. The dose required for 50% inhibition of P uptake was approximately two to three times higher for vanillic acid (6.73 mM) than for ferulic (2.27 mM) andp-coumaric acids (3.00 mM) when dose was based on the initial treatment concentrations. The dose required for 50% inhibition of P uptake was not significantly different for the three phenolic acids (42 ± 5 mol/g root fresh weight) when dose was based on phenolic acid uptake. Potential reasons for these differences are discussed.Paper No. 12527 of the Journal Series of the North Carolina Agricultural Research Service, Raleigh, North Carolina 27695-7643. The use of trade names in this publication does not imply endorsement by the North Carolina Agricultural Research Service of products named, nor criticism of similar ones not mentioned. This research was partially supported by the US-Spain Joint Committee for Scientific and Technological Cooperation project CCA-8309/166.     

Aggregation pheromone of palmetto weevil,Rhynchophorus cruentatus (F.) (Coleoptera: Curculionidae)

5-Methyl-4-octanol is the major aggregation pheromone of the palmetto weevil,Rhynchophorus cruentatus (F.). The pheromone (cruentol) was identified by coupled gas chromatographic-electroantennographic (GC-EAD) analysis of male-produced volatiles, coupled GC-mass spectrometry (MS) in electron impact and chemical ionization mode, and coupled GC-high resolution MS. In laboratory and field assays, a diastereomeric mixture of synthetic cruentol greatly enhanced attraction of weevils to cabbage palmetto,Sabal palmetto (Walter), stem tissue, indicating that cruentol and host volatiles are synergistically attractive. An attractive lure in combination with efficient traps should facilitate development of semiochemical-based management forR. cruentatus.     

(Z)-oxacyclotridec-10-en-2-one does not appear to be responsible for resistance to adult alfalfa weevil feeding exhibited byMedicago rugosa

Steam distillate prepared from leaves ofMedicago rugosa Desr. could inhibit feeding by adult alfalfa weevils (Hypera postica (Gyll.) on membrane filters, whereas an equivalent amount of steam distillate prepared usingM. sativa L. had no effect on weevil feeding. Earlier work established that a 12-carbon lactone, (Z)-oxacyclotridec-10-en-2-one, was responsible for the feeding deterrent properties of the steam distillate fromM. rugosa. The concentration of this volatile varied with plant age and leaf position. The maximum concentration in leaves ofM. rugosa (area basis) was estimated, on the basis of tests using an inert substrate, to be too low to cause a detectable inhibition of feeding. No correlation between lactone content and weevil feeding was detected when leaves from similar positions on plants of different ages were used in a multiple choice bioassay. Although small amounts (< 12.5g) of (Z)-oxacyclotridec-10-en-2-one can inhibit adult alfalfa weevil feeding on 13-mm-diameter membrane filters, because leaf concentrations (area basis) of this compound are lower than required to cause a detectable inhibition of feeding on the inert substrate, and because concentrations do not correlate with weevil feeding, it is unlikely that this lactone is responsible for resistance to adult alfalfa weevil feeding exhibited byM. rugosa.Mention of a trademark, proprietary product, or vendor does not constitute a guarantee or warranty of the product by the USDA and does not imply approval to the exclusion of other products or vendors that may also be suitable.Technical paper No. 9416 of the Agricultural Experiment Station, Oregon State University, Corvallis, Oregon 97331.     

Effects of Microbial Utilization of Phenolic Acids and their Phenolic Acid Breakdown Products on Allelopathic Interactions

Reversible sorption of phenolic acids by soils may provide some protection to phenolic acids from microbial degradation. In the absence of microbes, reversible sorption 35 days after addition of 0.5–3 mol/g of ferulic acid or p-coumaric acid was 8–14% in Cecil A_p horizon and 31–38% in Cecil B_t, horizon soil materials. The reversibly sorbed/solution ratios (r/s) for ferulic acid or p-coumaric acid ranged from 0.12 to 0.25 in A_p and 0.65 to 0.85 in B_t horizon soil materials. When microbes were introduced, the r/s ratio for both the A_p and B_t horizon soil materials increased over time up to 5 and 2, respectively, thereby indicating a more rapid utilization of solution phenolic acids over reversibly sorbed phenolic acids. The increase in r/s ratio and the overall microbial utilization of ferulic acid and/or p-coumaric acid were much more rapid in A_p than in B_t horizon soil materials. Reversible sorption, however, provided protection of phenolic acids from microbial utilization for only very short periods of time. Differential soil fixation, microbial production of benzoic acids (e.g., vanillic acid and p-hydroxybenzoic acid) from cinnamic acids (e.g., ferulic acid and p-coumaric acid, respectively), and the subsequent differential utilization of cinnamic and benzoic acids by soil microbes indicated that these processes can substantially influence the magnitude and duration of the phytoxicity of individual phenolic acids.     

Inducible Production of Phenolic Acids in Wheat and Antibiotic Resistance to Sitodiplosis mosellana

Larvae of the wheat midge, Sitodiplosis mosellana (Géhin) feed on the surface of wheat seeds for about 10 days beginning when pollination occurs. A few wheats have a high level of antibiotic resistance to the larvae, which suppresses their growth and development. Nearly all larvae develop successfully on susceptible wheats. Analysis by HPLC of seed extracts produced by alkaline hydrolysis revealed rapid changes in the levels of p-coumaric and ferulic acids during early seed development. Seed infested by wheat midge larvae showed induced changes in the dynamics of these phenolic acids. The most resistant wheats had a higher constitutive level and a more rapid induction of ferulic acid than susceptible wheats. Levels of ferulic acid exceeding 0.35 g/g fresh weight were associated with a high mortality of newly hatched larvae. In one wheat line, resistance also was associated with induced production of p-coumaric acid. The induction of ferulic acid was similar in wheat from the laboratory and field, except in one resistant wheat that produced higher levels in the field. In ripe seeds, resistant and susceptible wheats had similar levels of phenolic acids.     

Simultaneous effects of ferulic andp-coumaric acids on cucumber leaf expansion in split-root experiments

Experiments were conducted to determine how plant responses to mixtures of allelochemicals may change as the proportion of roots in contact with allelochemicals is modified. Thirteen-day-old cucumber seedlings were treated with ferulic and/orp-coumaric acid in a split-root nutrient culture system. Leaf areas were determined just prior to treatment and at harvest, 24 hr after treatment. Ferulic acid was more inhibitory to cucumber leaf expansion thanp-coumaric acid. The effects of ferulic andp-coumaric acids on leaf expansion were additive. For individual acids, mixtures of ferulic andp-coumaric acids in the same container and combinations of ferulic andp-coumaric acids in separate containers, the inhibition of leaf expansion was directly related to the product of the concentration of the acid(s) and the proportion of roots treated with the acid(s). Pretreatment with 0.2 or 0.4 mM ferulic acid and subsequent treatment with 0.5 mM ferulic acid failed to show evidence of acclimation by cucumber seedlings.The use of trade names in this publication does not imply endorsement by the North Carolina Agricultural Research Service of products named, nor criticism of similar ones not mentioned.