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advid bud-feeding insects cutworms and vine weevils associação para o desenvolvimento da vi cultura duriense · douro region wine cluster information bulletin 04-10 april 2010 introduction bud-feeding insects in the douro are of relative importance depending on the location quantity and type of existing weeds and also the cultural techniques used to control these weeds although these insects appear sporadically the damage they create may nonetheless reach catastrophic dimensions when biological factors of the pest are combined with the application of herbicides morphology/biology cutworms ­ agrotis sp noctua sp and spodoptera exigua ­ are in their immature stage in which they cause damage night-feeding larvae measuring up to 5 cm in length 2-3 cm being the length most commonly observed by winegrowers fig 1 when disturbed they curl up to reduce their size and avoid being noticed there are several species of cutworms and the colour of the larvae vary from light green to dark brown generally with a whitish stripe on each side in the adult stage they are moths with an average wingspan of 4 to 5 cm in a wide range of colours depending on the species although they generally have patterned wings the vine weevil ­ otiorhynchus sulcatus ­ is in the adult stage a night-flying insect with a dark hard-shell body with white spots and a length of approximately 1 cm fig 2 the whitish larvae are soildwelling although most species have only a single generation some may develop a second or even a third generation which may give rise to larvae attacks on the cluster at the time of the grape harvest on very rare fig 3 bud attacked by cutworm fig 4 shoot with attacked tip advid · quinta de santa maria · apartado137 · 5050-106 godim peso da régua · tel +351 254 312940 · fax +351 254 321350 · e-mail advid@advid.pt · www.advid.pt fig 1 cutworm larva fig 2 adult vine weevil occasions both insects complete their annual cycle on weeds existing in the vineyard or around its edges symptoms/damage these insects generally operate at a specific stage of the grapevine growth cycle budbreak spending the rest of the year unnoticed during this period generally after weeds have been eliminated the cutworm larvae move into the grapevines feeding mainly on their buds a single larva can eat five to six buds a night until all the buds on the grapevine are eliminated the larvae may also chew the ends of small shoots or foliage fig 3 the damage caused by vine weevils in this case by adults is frequently mistaken for damage by cutworms and it is sometimes difficult to establish which of the two insects caused the particular damage like cutworms this insect feeds on both buds and small shoots the larvae which are soil-dwelling may also attack the plant s smaller roots this damage being more significant in new plantations or in nurseries this damage is more severe in years in which low temperatures occur after the start of budbreak thus extending the vine s period of susceptibility in both cases the damage is made during the night or else on very cloudy days during the day cutworm larvae or vine weevils can be found at the base of the vine stock under stones dry foliage under the vine bark or even camouflaged by the vine stock itself due to their dark colours.

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favourable conditions as already mentioned cutworms and vine weevils are insects that hibernate and feed on weeds in the spring when weeds are controlled late through an application of herbicide or at any other time when the existence of weeds is conditioned a dry winter these pests move into the vines where they feed voraciously indeed the systematic application of herbicides immediately before or at the start of budbreak is a factor that can intensify attacks however even without the application of herbicides damage has been observed on vines it is known however that the presence of larvae depends on the presence of autumn-winter weeds necessary for their development the existence of scrub or natural areas in the vicinity of the block may also contribute to the existence of this pest on grapevines cultural control tests carried out in the douro branco fernandes 1986 mention as preventive cultural practices the complete clearing of weeds during the period from late summer to budbreak this study noted that where vineyards were kept completely clear of weeds they were not attacked by cutworms unlike vineyards where herbicide had only been applied in late winter/early spring in integrated production this practice is not recommended for which reason the ideal would be to avoid the application of herbicides during budbreak to the greatest extent possible on blocks that are traditionally attacked it would be advisable not to totally eliminate weeds leaving strips of grass in their vicinity to prevent these insects from exclusively attacking the grapevine chemical control before taking the decision to apply insecticide treatment to control these pests various factors must be considered 1 the eil economic injury level defined for cutworms is 2-3 of vine stocks with symptoms and farmers should take into account nuisance factors existing climate conditions existence of labour time and machinery available treatment cost etc since the effectiveness of insecticide treatment is often questioned 2 at present there are no approved products to control cutworms and this is also a nuisance factor sulphur may have a certain repellent effect on this type of insect in the case of vine weevils coleoptera curculionidae note should be made of the recent approval of the active substance deltamethrin see list of approved insecticide in ip when taking a decision concerning the application of an insecticide it is recommended that the application be limited to affected vines and adjacent vines using high flowrates whenever possible aiming the jet so that the surplus mixture not remaining on the grapevine falls on the base of the vine stock where the insects can be found during the day the nozzles used should preferably produce large droplets full cone jet nozzles the application should be made as close as possible to the evening so that when the insects rise to create damage they are in contact with as much product as possible interventions are only justified when blocks have a history of attacks when the presence of the pest is observed and during the vine s susceptibility period since when shoots develop reaching a length of 5 to 10 cm these pests cease to cause problems bibliography branco j.m fernandes j.d 1986 prevenção dos estragos de noctua spp em vinhas do douro com herbicidas cnppa lisbon 14 pp cavaco m calouro f clÍmaco p 2005 produção integrada da cultura da vinha dgpc oeiras 146 pp note please contact the advid technical department with any queries concerning other pests with symptomatology similar to that caused by cutworms and vine weevils fig 4 damaged bud alongside intact buds fig 5 cutworm larva fig 6 spur with buds all damaged by vine weevils table 1 methodology for estimate of cutworm risk and eil for portugal cavaco et al 2005 pest cutworms agrotis sp risk estimate observation season stages b-c sampling method visual observation parts to be observed 100 vine stocks eil from 2-3 of vine stocks with symptoms publishing details coordina on fernando alves texts cris na carlos fernando alves photos cris na carlos advid produc on and prin ng advid april 2010 print run 250 copies advid · quinta de santa maria · apartado137 · 5050-106 godim peso da régua · tel +351 254 312940 · fax +351 254 321350 · e-mail advid@advid.pt · www.advid.pt

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