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Abstract. A Y-tube olfactometer and a still-air olfactometer were developed to determine the attractiveness of several host plants for the vine weevil (Otiorhynchus sulcatus (F.); Coleoptera: Curculionidae). Odours of weevil-damaged yew (Taxus baccata) and spindle trees (Euonymus fortunei) are attractive to the vine weevil, but Rhododendron and strawberry (Fragaria  ananassa) are not. Undamaged Euonymus is attractive to the weevils in springtime but not in late summer. When clean air or undamaged Euonymus is the alternative, weevils strongly prefer weevil-damaged Euonymus foliage, and this preference is retained throughout the year. Hence, plant damage plays a role in attraction of the vine weevil. In contrast to the permanent attractiveness of weevil-damaged Euonymus, mechanically damaged plants gradually lose the attractiveness that they have early in the growing season. This suggests that emission of volatiles, produced by the plants in response to weevil damage, is important for attraction of the weevils because the weevils may use these plant odours to find suitable food plants throughout the season. Apart from weevil-damage-related plant volatiles, green leaf volatiles must also play a significant role, as indicated by the fact that weevils prefer: early season, undamaged Euonymus over clean air; early season, mechanically damaged Euonymus over undamaged Euonymus; and, throughout the season, had no preference when mechanically damaged Euonymus is tested against weevil-damaged Euonymus. Thus, monitoring traps may be developed by the use of green leaf volatiles and/or herbivore-induced volatiles, as attractants.

Root weevils in the genus Otiorhynchus are cited as one of the most important pests in the major nursery and small fruit production areas throughout the United States, western Canada, and northern Europe. A major problem in combating weevil attack is monitoring and timing of control measures. Because of the night-activity of the adult weevils growers do not observe the emerging weevils in a timely manner and oviposition often starts before effective control measures are taken. Several vine weevil electroantennogram-active plant volatiles were identified from a preferred host plant, Euonymus fortunei. Main compounds evoking antennal responses on the weevils' antennae were (Z)-2-pentenol, (E)-2-hexenol, (Z)-3-hexenol, methyl benzoate, linalool, (E)-4,8-dimethyl-1,3,7-nonatriene, methyl eugenol, and (E, E)-alpha-farnesene. Several of these compounds were tested alone and in mixtures on attractiveness for the vine weevil Otiorhynchus sulcatus (F.) in field-grown strawberry in Oregon. O. sulcatus were attracted to (Z)-2-pentenol (approximately 3 x more than control) and a 1:1 ratio mixture of (Z)-2-pentenol and methyl eugenol (4.5 x more than control). This is the first report of field-active attractants for O. sulcatus which holds promise for the development of new monitoring strategies for growers in the near future.

We compared the efficacy of four plant essential oils to repel onion thrips, Thrips tabaci (Lindeman) (Thysanoptera: Thripidae), in the presence of an attractive odour, ethyl iso -nicotinate in a pasture field. Four horizontal white sticky plates were placed adjacent to (directions: N, S, E, W) a central horizontal white plate (C). After 24 h, in the treatment combination where the four plates were sprayed with essential oil surrounding a central sticky plate sprayed with ethyl iso -nicotinate, fewer onion thrips were found on the plates treated with sweet marjoram [ Origanum majorana L. (Labiatae)] or clove basil [ Ocimum gratissimum L. (Labiatae)] (87 and 71% less, respectively) compared to the control treatment of four water-sprayed plates surrounding a central plate with ethyl iso -nicotinate. We also compared the distribution of onion thrips on the plates. Relative thrips numbers on each plate were compared with similar (N, S, E, W, and C) plates in the control treatment. There were relatively lower thrips numbers on the south (23% reduction) and west (26% reduction) O. majorana -treated plates and higher numbers (37% increase) on the central attractant-treated plate indicating a shortdistance push-pull effect. When four plates were sprayed with the thrips attractant surrounding a central sticky plate sprayed with an essential oil or water (control), only O. majorana reduced the number of thrips on the attractant-sprayed plates (62% reduction). The distribution of thrips on the different plates within this treatment combination did not change substantially when compared to the distribution in the water-control treatment. Other essential oils tested (wormwood [ Artemisia arborescens L. (Compositae)]) and tea tree [ Melaleuca alternifolia (Maiden. & Betche.) Cheel. (Myrtaceae)]) were not effective in any of the treatments. It appears that O. majorana is a promising thrips repellent which could be used for further testing in a push-pull system with the attractant ethyl iso -nicotinate. The field setup used also proved to be a valuable tool for evaluating the potential of repellents to control onion thrips.

1 The relationship between reproductive performance and preference for potential host plants of the vine weevil is investigated, as shown in tests on contact (or feeding) preference, presented herein, and tests on olfactory preference, published elsewhere. 2 Assessment of reproductive performance shows that the host-plant range of the adult vine weevil Otiorhynchus sulcatus in Europe is limited to one gymnosperm genus (Taxus sp.) and a broad range of angiosperm plants in two subclasses of the Dicotyledonae, namely Dilleniidae and Rosidae. The successful reproduction on very distantly related plant taxa suggests that the original weevil-and plant-habitat has mediated the current host-plant range of the vine weevil. 3 Contact-preference tests with equally suitable hosts, such as Aronia, Fragaria, Euonymus and Taxus, and one less suitable host, Humulus, indicate a mismatch between contact preference and performance and, as far as olfactory preferences are known, these match neither the contact preferences nor the performance. This mismatch may arise because (i) host plant species offered do not occur in weevil habitat in Europe (e.g. Aronia and the cultivated Fragaria come from North America) and (ii) predation (or disease) risks differ among host plants, thereby altering effective reproductive performance. 4 With respect to performance on novel hosts (Thuja, Prunus) and bad hosts (Rhododendron), some between-individual variation is found within a single population, suggesting that local populations harbour (possibly genetic) variation for adaptation to new hosts. How this variation is maintained in the face of strong selection pressures on local populations of flightless and thelytokous weevils, is an important question for understanding the broad host plant range in the vine weevil.

BACKGROUNDThe effect of spatial separation of the semiochemical Lurem‐TR, which has been found to inhibit conidia of entomopathogenic fungi when put together, on the persistence of conidia of Metarhizium brunneum and M. anisopliae was evaluated in the greenhouse and field in order to develop an autodissemination strategy for the management of Megalurothrips sjostedti on cowpea crop. Influence of spatial separation of the semiochemical on thrips attraction and conidial acquisition by thrips from the autoinoculation device was also investigated in the field.RESULTSPersistence of conidia of M. brunneum and M. anisopliae increased with distance of separation of Lurem‐TR. Direct exposure of fungus without separation from Lurem‐TR recorded the lowest conidial germination as compared with the other treatments. Attraction of thrips to the device also varied significantly according to distance between device and semiochemical, with a higher number of thrips attracted when Lurem‐TR was placed in a container below the device and at 10 cm distance. There was no significant difference in conidial acquisition between spatial separation treatments of conidia and Lurem‐TR. Attraction of other insect pests to the device did not significantly vary between treatments. Positive correlations were found between conidial acquisition and thrips attraction.CONCLUSIONThis study suggests that spatial separation of fungal conidia from Lurem‐TR in an autoinoculation device could provide a low‐cost strategy for effective management of thrips in grain legume cropping systems. © 2015 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Methyl isonicotinate is one of several patented 4-pyridyl carbonyl compounds being investigated for a variety of uses in thrips pest management. It is probably the most extensively studied thrips non-pheromone semiochemical, with field and glasshouse trapping experiments, and wind tunnel and Y-tube olfactometer studies in several countries demonstrating a behavioural response that results in increased trap capture of at least 12 thrips species, including the cosmopolitan virus vectors such as western flower thrips and onion thrips. Methyl isonicotinate has several of the characteristics that are required for an effective semiochemical tool and is being mainly used as a lure in combination with coloured sticky traps for enhanced monitoring of thrips in greenhouses. Research indicates that this non-pheromone semiochemical has the potential to be used for other thrips management strategies such as mass trapping, lure and kill, lure and infect, and as a behavioural synergist in conjunction with insecticides, in a range of indoor and outdoor crops.