RESUMEN

Understanding the stimuli used by insect pests to find their food plants can be a first step towards manipulating their behaviour and, thus, controlling them. We investigated the responses of the sugar beet weevil Asproparthenis punctiventris (Coleoptera: Curculionidae) to the volatile leaf odours of its food plants, including Beta vulgaris subsp. vulgaris (Altissima and Cicla groups), Atriplex hortensis, Chenopodium album, and Amaranthus retroflexus, in a four-arm olfactometer. A bioassay procedure was developed, and the frequency of visits and time spent by adult weevils in the quadrant of the olfactometer with leaf volatiles was recorded, as was their first choice of quadrant. Females and males were equally attracted to the leaf odours of young B. vulgaris subsp. vulgaris plants, i.e., sugar beet and chard, as indicated by the overall picture of the behavioural parameters analysed. Males, but not females, responded positively to the leaf odour of the garden orache (A. hortensis), and no response was observed when the weevils were tested with the leaf odours of fat hen (C. album) or common amaranth (A. retroflexus). These results suggest that A. punctiventris uses leaf odours to locate sugar beet and other food plants. Knowledge of the olfactory responses of this pest can provide a basis for improved monitoring or mass trapping strategies.

RESUMEN

BACKGROUND: The invasive insect Drosophila suzukii (Matsumura) is an important pest of several red grape varieties. The yeast Hanseniaspora uvarum (Niehaus), which is associated with D. suzukii, strongly attracts flies and stimulates them to feed on yeast-laden food. In the present study, a formulation based on H. uvarum culture with spinosad insecticide was applied to the foliage of vineyards and control of D. suzukii was compared to applying spinosad to the whole plant. After successful H. uvarum and insecticide application in the vineyard, we tested additional H. uvarum-based formulations with spinosad in a greenhouse to determine their capacity to control D. suzukii. RESULTS: Application of the H. uvarum-spinosad formulation at 36.4 g of spinosad per hectare reduced the D. suzukii field infestation at the same rate as applying 120 g of spinosad per hectare and prevented spinosad residues on grapes. Leaves treated with H. uvarum and spinosad in the field and transferred to a laboratory assay caused high mortality to flies and reduced the number of eggs laid on fruits. Formulations with spinosad applied in the greenhouse showed that both H. uvarum culture and the yeast cell-free supernatant of a centrifuged culture increased fly mortality and reduced the number of eggs laid compared to the unsprayed control. CONCLUSION: In comparison to typical spinosad spray applications, the use of H. uvarum in combination with spinosad as an attract-and-kill formulation against D. suzukii reduces pesticide residues on the fruits by targeting the treatment to the canopy and decreasing the amount of insecticide per hectare without compromising control efficacy.

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RESUMEN

Thrips (Thysanoptera) are small insects that can cause huge problems in agriculture, horticulture, and forestry through feeding and the transmission of plant viruses. They produce a rich chemical diversity of pheromones and allomones and also respond to a broad range of semiochemicals from plants. These semiochemicals offer many opportunities to develop new approaches to pest management. Aggregation pheromones and plant-derived semiochemicals are already available in commercial products. We review these semiochemicals and consider how we can move away from using them mainly for monitoring to using them for control. We still know very little about the behavioral responses of thrips to semiochemicals, and we show that research in this area is needed to improve the use of semiochemicals in pest management. We also propose that thrips should be used as a model system for semiochemically mediated behaviors of small insects that have limited ability to fly upwind.

Asunto(s)

RESUMEN

The larval stages of Frankliniella occidentalis Pergande (Thysanoptera: Thripidae) cause more direct feeding damage to plants than the adults. We, therefore, investigated the behaviour-modifying effects on second instar larvae of two jasmonic acid derivatives. The artificial application of methyl jasmonate and cis-jasmone, both at 1 % concentration, deterred the larvae from settling in a dual choice bean leaf disc assay. We observed a dose-dependent feeding deterrence of both jasmonates and calculated the concentration required to reduce the feeding damage by 50 % relative to the control treatment (FDC50) for each jasmonate. The feeding damage was reduced by the application of cis-jasmone at 1 % concentration, but not by the jasmonates at the respective FDC50 in no-choice leaf disc bioassays. However, significantly more larvae left jasmonate-treated whole potted bean plants by migrating to the soil compared with control plants. Our results may be exploited extending behavioural manipulation by using plant compounds in thrips control programmes to the full lifecycle of the pest. Plant compounds could be used in integrated and biological pest management strategies against F. occidentalis in combination with the application of various above and below ground control measures.