Allan C. Oehlschlager

Enzyme reactions in apolar solvents: the resolution of (±)-sulcatol with porcine pancreatic lipase.

Abstract The enantioselectivity of the transesterification of (±)-sulcatol by porcine pancreatic lipase in ether is increased ten-fold by dehydration of the enzyme and use of 2,2,2-trifluoroethyl laurate as the ester.

Chemical and Behavioral Ecology of Palm Weevils (Curculionidae: Rhynchophorinae)

Palm weevils in the subfamily Rhynchophorinae (Curculionidae) (Rhynchophorus spp., Dynamis borassi, Metamasius hemipterus, Rhabdoscelus obscurus, and Paramasius distortus) use male-produced aggregation pheromones for intraspecific chemical communication. Pheromones comprise 8, 9, or 10 carbon, methyl-branched, secondary alcohols. (4S,5S)-4-Methyl-5-nonanol (ferrugineol) is the major aggregation pheromone for R. ferrugineus, R. vulneratus, R. bilineatus, M. hemipterus, and D. borassi and a minor component for R. palmarum. (5S,4S)-5-Methyl-4-octanol (cruentol), (3S,4S)-3-methyl-4-octanol (phoenicol), and (4S,2E)-6-methyl-2-hepten-4-ol (rhynchophorol) are the main aggregation pheromones for R. cruentatus, R. phoenicis, and R. palmarum, respectively. Plant kairomones strongly enhance pheromone attractiveness but none of the identified volatiles, such as ethyl acetate, ethyl propionate, or ethyl butyrate are as synergistic as fermenting plant (palm or sugarcane) tissue. Studying orientation behavior of foraging weevils to semiochemical devices helped to design and test traps for weevil capture. Generally, 3 mg per day of synthetic pheromone (with non-natural stereoisomers being benign) plus insecticide-treated plant tissue constitute highly attractive trap baits. Potential exists for pheromone-based mass-trapping of weevils to reduce their populations and the spread of the weevil-vectored red ring disease, for monitoring their population dynamics to facilitate pest management decisions, and for detection and possible interception of non-native weevils at ports of entry.

Control of red ring disease by mass trapping of Rhynchophorus palmarum (Coleoptera: Curculionidae).

Abstract Rhynchophorus palmarum (L), the American palm weevil, is an important pest of several palm species in tropical America as a vector of the red ring nematode Bursaphelenchus cocophilus Cobb. Bimonthly inspections coupled with elimination of red ring diseased (RRD) oil palms (Elaeis guineensis Jacq.) failed to reduce infection rates of oil palms in two commercial plantations in Costa Rica. Addition of pheromone-based trapping of R. palmarum using trap densities of less than one trap per five hectares lowered RRD in both plantations by over 80% in one year. Continued removal of RRD infected palms and trapping maintained RRD at very low levels over several years. No matter what the initial RRD infection level, trap density or capture rate, areas with high and areas with low RRD infection levels declined to the same low RRD infection level after one year of trapping. An efficient strategy for management of RRD in oil palm is based on an integrated approach where RRD and other diseased (e.g., spear rot) palms are promptly eliminated or properly treated and pheromone-baited traps are used to reduce populations of R. palmarum. These strategies are complimented by removal of weevil-infested palms after wind and lightning damage and periodic removal of palms (e.g., coconut palms) in surrounding areas that serve as hosts for R. palmarum.

FIELD RESPONSE OF RHYNCHOPHORUS CRUENTATUS (COLEOPTERA: CURCULIONIDAE) TO ITS AGGREGATION PHEROMONE AND FERMENTING PLANT VOLATILES

Semiochemicals from 2.5 kg of chopped stem tissue from cabbage palmetto, Sabal palmetto (Walter), frozen or fresh stem tissue from sugarcane, Saccharum officinarum L., or syncarp tissue from pineapple, Anana comosus (L.), were equally suitable for field attraction of Rhynchophorus cruentatus (F.) when used with 0.4 mg/d of its aggregation pheromone, 5-methyl-4-octanol (cruentol). Twenty-eight different chemicals known to be fermentation products from palm sap were screened with 0.4 mg/d cruentol for field attraction of R. cruentatus adults. Good chemically-mediated field trapping of R. cruentatus was achieved with cruentol plus ethyl acetate (852 mg/d) and to a lesser degree with each of the following: (S)-(-)-ethyl lactate (release rate not determined; ND), ethyl isobutyrate (40 mg/d), ethyl butyrate (255 mg/d), or ethanol (51 mg/d). However, none of the test chemicals with cruentol were as effective as 1.5 kg of fermenting sugarcane or S. palmetto tissue plus cruentol. Also, none of these chemicals were attractive by themselves at the rates tested. A combination of individually released ethanol (48 mg/d), ethyl acetate (131 mg/d), ethyl butyrate (34 mg/d), ethyl isobutyrate (40 mg/d), and (S)-(-)-ethyl lactate (ND) with cruentol was as effective for the capture of R. cruentatus as cruentol plus any of the individual components at the rates tested. Several trap designs were evaluated for future research and implementation of semiochemically-mediated monitoring and management of R. cruentatus.

Monoterpene metabolism in female mountain pine beetles, Dendroctonus ponderosae Hopkins, attacking ponderosa pine

Abdominal volatiles of female mountain pine beetles,Dendroctonus ponderosae Hopkins, fed in ponderosa pine,Pinus ponderosa Dougl. ex Laws, and in lodgepole pine,P. contorta var.latifolia Engelmann, were analyzed by gas chromatography and coupled gas chromatography-mass spectrometry and were found to comprise host oleoresin components and beetle-produced alliylic alcohols, aldehydes, and ketones derived from host monoterpenes. Neitherexo- andendo-brevicomin nor frontalin were detected. Three metabolic pathways are proposed to account for the distribution of beetle-produced monoterpene alcohols. The first pathway involves hydroxylation of monoterpene substrates on allylic methyl groups which areE to a methylene or vinyl group. This oxidation pathway is indiscriminate with respect to substrate and probably functions to detoxify monoterpenes. A second pathway, which hydroxylates theendo-cyclic methyleneE to a vinyl methyl group of bicyclic monoterpenes to give almost exclusively thetrans alcohol, is hypothesized to be involved in pheromone production. A third detoxification pathway involves anti-Markovnikov addition of water to theexo-cyclic double bond of β-phellandrene to give predominantlytrans-2-p-menthen-7-ol.

Isolation and identification of two macrolide pheromones from the frass ofCryptolestes ferrugineus (Coleoptera: Cucujidae).

Two synergistic macrolide aggregation pheromones were isolated from Porapak Q-trapped volatiles obtained from the frass ofCryptolestes ferrugineus (Stephens). These compounds were identified as (E,E)-4,8-dimethyl-4,8-decadien-10-olide (I) and (3Z,11S)-3-dodecen-11-olide (II) and given the trivial names ferrulactone I and II, respectively. Analysis of captured volatiles from separated male and female adults disclosed that the pheromones are male-produced. Additional macrolides were identified in frass volatiles, but were devoid of any pheromonal activity. The structures of I and II were confirmed by comparison with synthetic materials.

Pheromone production by axenically rearedDendroctonus ponderosae andIps paraconfusus (Coleoptera: Scolytidae).

Mountain pine beetles,Dendroctonus ponderosae Hopkins, and California five-spined ips,Ips paraconfusus Lanier, were reared axenically from surface-sterilized eggs on aseptic pine phloem. After 24 hr in host logs, axenip femaleD. ponderosae and maleI. paraconfusus produced the aggregation pheromones,trans-verbenol (D. ponderosae), and ipsenol and ipsdienol (I. paraconfusus). Emergent, axenically reared maleD. ponderosae contained normal amounts of the pheromoneexo-brevicomin. Axenic femaleD. ponderosae treated with juvenile hormone or exposed to vapors of α-pinene, produced the pheromonetrans-verbenol. By 25–35 days after eclosion, axenic females exposed to α-pinene vapors produced over six times as muchtrans-verbenol as wild females, suggesting that while microorganisms in wild females may producetrans-verbenol, they may also inhibit production of the pheromone or use it as a substrate.

Chemical communication in cucujid grain beetles

Males of five sympatric species of economically damaging cucujid grain beetles,Cryptolestes ferrugineus (Stephens),C. pusillus (Schönhen),C. turcicus (Grouvelle),Oryzaephilus mercator (Fauvel), andO. surinamensis (L.), produce macrolide aggregation pheromones especially in the presence of food. Work leading to the isolation, identification, and establishment of biological activity of these semiochemicals is reviewed. The trivial name “cucujolide” is proposed and used to identify these compounds that are characteristic of the Cucujidae. The twoOryzaephilus share species share a common cucujolide pheromone, whileCryptolestes species use cucujolides that are either enantiomeric, unique to the genus, or released in trace quantities byOryzaephilus spp. and not used as pheromones by the latter species. The major mechanisms for species specificity in chemical communication are: (1) presence of a unique pheromone (C. ferrugineus andC. pusillus); (2) use of pheromones that are inactive alone but synergize response to cucujolides unique to a species (C. pusillus, C. turcicus, andO. surinamensis); (3) response to only one enantiomer of a pheromone (C. ferrugineus, O. surinamensis, andO. mercator); and (4) synergism between enantiomers of a pheromone (C. turcicus). The only species for which cross-attraction was evident wasO. mercator toO. surinamensis. Both sexes ofOryzaephilus spp. produce (R)-1-octen-3-ol, which highly synergizes response to the cucujolide pheromones. Similar synergism occurs between hexanal, octanal, and nonanal and the cucujolide pheromones ofOryzaephilus spp. The males of a sixth cucujid species,Cathartus quadricollis (Guér) produce a different aggregation pheromone, (3R,6E)-7-methyl-6-nonen-3-yl acetate. Trapping ofCryptolestes andOryzaephilus spp. in cardboard traps baited with pheromones is efficient in environments mimicking food-storage areas. Pheromone-baited plastic probe traps are the most efficient at capturing these species in infested grain.

Chirality and field activity of rhynchophorol, the aggregation pheromone of the American palm weevil

The American palm weevil, Rhynchophoruspalmarum (L.) (Coleoptera: Curculionidae), is the major vector of Rhadinaphelenchus cocophilus, a nematode which causes red ring disease in oil and coconut palms throughout Central and South America [1]. Losses to this disease are significant, and its incidence has been correlated with weevil population density [1]. Trapping with insecticide-treated pieces of palm is practiced but traps lose their attractancy after a few days [2]. Therefore, the availability of a stable semiochemical to enhance trap attractancy would be of significant value in control of this pest. Recently, Rochat et al. [3] reported the identification and laboratory activity of a male-produced aggregation pheromone, 6-methyl-2(E)-hepten-4-ol (1) for this weevil. Weevils were collected on sawn sections of oil palm trunk in the Palma Tica plantations at Quepos and Coto 47, Costa Rica. They were maintained in laboratory cultures on fresh sugarcane or apples. Volatiles were collected by drawing air over 20 25 male or female R. palmarum in a Nalgene desiccator fitted with a charcoal filter at the inlet and a Porapak Q trap at the outlet. Aerations were carried out for 2 4 days at a flow rate of 85 1/h [4]. Trapped volatiles were extracted from the Porapak Q with pentane which was concentrated by distillation [4]. Gas chromatographic analysis conducted

Aggregation pheromones and host kairomones of West Indian sugarcane weevil, Metamasius hemipterus sericeus

Coupled gas chromatographic–electroantennographic detection (GC-EAD) analyses and coupled GC-mass spectrometry (MS) of volatiles produced by male and female West Indian sugarcane weevils (WISW), Metamasius hemipterus sericeus (Oliv.), revealed eight male specific, EAD-active compounds: 3-pentanol (1), 2-methyl-4-heptanol (2), 2-methyl-4-octanol (3), 4-methyl-5-nonanol (4), and the corresponding ketones. In field experiments in Florida, alcohols 1–4 in combination with sugarcane were most attractive, whereas addition of the ketones or replacement of alcohols with ketones significantly reduced attraction. In Costa Rica field experiments testing alcohols 1–4 singly and in all binary, ternary, and quaternary combinations revealed 4 in combination with 2 was the major aggregation pheromone, equally attracting male and female WISW. Stereoisomeric 4 and (4S,5S)-4, the only isomer produced by WISW, were equally attractive. Addition of 4S-, 4R- or (±)-2 to (4S,5S)-4 significantly enhanced attraction. Sugarcane stalks in combination with 2 plus 4 (ratio of 1:8) were highly synergistic, whereas EAD-active sugarcane volatiles ethyl acetate, ethyl propionate, or ethyl butyrate only moderately increased attractiveness of the pheromone lure.