Carlo Duso

Mite population dynamics on different grape varieties with or without phytoseiids released (Acari: Phytoseiidae).

In a three-year study, mite populations were monitored in two vineyards, each having two grape varieties with different leaf hair density. In both vineyards native phytoseiids were present: Amblyseius andersoni in one vineyard, and Phytoseius finitimus in the other. The economically important predators Kampimodromus aberrans and Typhlodromus pyri were released in both vineyards in order to study their efficacy in controlling tetranychids and eriophyids and their persistence during periods of prey scarcity. In both vineyards, relative abundances of the mite species, especially phytoseiids, were found to differ on different varieties in the same vineyard. In the first experiment, A. andersoni reached higher densities and was more persistent on the variety with slightly pubescent leaf under-surface (Merlot). Typhlodromus pyri and K. aberrans releases were successful and the mites became more abundant on the variety with pubescent leaf under-surface (Verduzzo). In the second experiment, P. finitimus was more abundant on a variety with pubescent leaf under-surface (Prosecco) than with glabrous leaf under-surface (Riesling). The most interesting results of the present study concerned the interactions between native and released predators. In the first vineyard, different results were obtained when releasing T. pyri on the two varieties. On the variety with pubescent leaves, A. andersoni was rapidly displaced by T. pyri, whereas the former species persisted on the other variety throughout the three-year study, apparently becoming dominant during the last season. In contrast to T. pyri, interactions between K. aberrans and A. andersoni in this vineyard did not depend on variety. The results of the experiments carried out in the second vineyard stressed the importance of interspecific competition for phytoseiid releases. Typhlodromus pyri colonization failed on both varieties. Kampimodromus aberrans releases appeared to be more successful on Riesling than on Prosecco, where P. finitimus was more abundant. At the end of the experiments, K. aberrans displaced P. finitimus on both varieties.

Toxicity of some insecticides to Tetranychus urticae, Neoseiulus californicus and Tydeus californicus

Three mite species are frequently found on vegetable crops in Italy: the pest Tetranychus urticae Koch (Acari: Tetranychidae), the predator Neoseiulus californicus (McGregor) (Acari: Phytoseiidae) and the unspecialised feeder Tydeus californicus (Banks) (Acari: Tydeidae). In laboratory trials, the direct and residual effects of six insecticides recommended for the control of aphids, whiteflies and thrips in vegetable crops, (Biopiren® plus (pyrethrins), Confidor® (imidacloprid), Oikos® (azadirachtin), Plenum® (pymetrozine), Naturalis® (Beauveria bassiana) and Rotena® (rotenone)), were evaluated for the three mite species. All the products affected the mites and their effect was often favourable towards T. urticae and unfavourable towards N. californicus and T. californicus. Rotenone was more toxic to eggs than females of T. urticae. It was highly toxic to N. californicus and caused the death of all treated females of T. californicus. Pyrethrins and imidacloprid increased T. urticae fecundity, but decreased fecundity of N. californicus. Imidacloprid decreased T. californicus fecundity more than pyrethrins. Beauveria bassiana was not toxic to T. urticae and T. californicus, but induced high mortality in the progeny of treated females of N. californicus. Azadirachtin and pymetrozine were the least toxic to T. urticae and N. californicus, but decreased production of larvae in T. californicus. Implications for integrated pest management on vegetables are discussed.

Developmental times and oviposition rates of predatory mites Typhlodromus pyri and Amblyseius andersoni (Acari: Phytoseiidae) reared on different foods

The developmental times and the reproduction of two resistant Italian strains ofTyphlodromus pyri Scheuten andAmblyseius andersoni (Chant) were studied in the laboratory by rearing them on the spider mitesPanonychus ulmi (Koch) andEotetranychus carpini (Oud.), on the eriophyidColomerus vitis (Pgst.) and on pollen ofMesembryanthemum criniflorum. The response ofT. pyri andA. andersoni females to a spider mite supply (P. ulmi orE. carpini) of 4, 8 and 16 adult female prey per female predator per day was also studied.Development ofT. pyri onE. carpini andC. vitis required a shorter period than onM. criniflorum pollen, while intermediate values were recorded forP. ulmi. When the highest number of prey was offered, the influence of different foods on oviposition rates ofT. pyri was not significant. An increase in spider mite supply favoured a shorter pre-oviposition period and higher oviposition rates.Development ofA. andersoni was faster on pollen than on spider mites, while intermediate values were found concerningC. vitis. Differences statistically significant were recorded for development onP. ulmi andC. vitis. Colomerus vitis proved to be the more suitable food in terms of oviposition. The oviposition rate decreased when feeding uponP. ulmi, but reached intermediate values onE. carpini andM. criniflorum. Increasing spider mite densities caused shorter pre-oviposition times and higher oviposition rates. Using a given number ofE. carpini females, rather than those ofP. ulmi, resulted in higher oviposition rates and shorter pre-oviposition times.For both predators, the results suggest a higher intrinsic rate of population increase onE. carpini orC. vitis than onP. ulmi.

Pollen availability and abundance of predatory phytoseiid mites on natural and secondary hedgerows

Mites occurring on a number ofnatural and secondary (i.e., planted) hedgerowslocated in north-eastern Italy were monitoredwith particular attention being paid tophytoseiids (Acari: Phytoseiidae). Pollendiversity and abundance were analysed tohighlight potential relationships betweenpollen availability and phytoseiids. Secondaryhedgerows were structured in modules containinga single species (field maple, hornbeam,dogwood, hazel, and elderberry) andmodules containing a mixture of theabove-mentioned species. These hedgerows werelocated in an experimental farm where they werecontiguous to a vineyard. Natural hedgerowswere located in the same area. The pollen ofPoaceae was the most important component ofnon-arboreal pollen (NAP), and that ofelderberry of arboreal pollen (AP). Pollendiversity was higher on natural than onsecondary hedgerows. Generally, pollendensities reached relatively high levels fromlate April to late June and decreased insummer. Pollen was more abundant on naturalthan on secondary hedgerows and phytoseiidabundance showed a similar trend. On elderberryand hornbeam in natural hedgerows a potentialrelationship between pollen availability andthe abundance of phytoseiids, in particular ofEuseius finlandicus (Oudemans) was found.Experimental pollen applications increased thefecundity and the abundance of this species.

Factors affecting the potential of phytoseiid mites (Acari: Phytoseiidae) as biocontrol agents in North-Italian vineyards

The results of a 5-year study on the relationships between spider mites and their predators in vineyards in Northern Italy are reported. The efficacy of the two predatory mites appeared to be strongly affected by various factors (grape variety, presence of macropredators, climatic condition, interspecific competition, phytoseiid strain).The phytoseiid mitesAmblyseius aberrans (Oud.) andTyphlodromus pyri Scheuten were released at three different density levels in two vineyards (A, B) infested byEotetranychus carpini (Oud.). One strain ofA. aberrans and two strains ofT. pyri were used for the experiments. In vineyard A,Panonychus ulmi (Koch) was recorded in the second and subsequent years of the experiments and became dominant overE. carpini from the third year onwards. The presence of anthocorids in the same vineyard increased the complexity of the system and gave us the possibility of comparing two very different situations.Release of low numbers ofA. aberrans gave a satisfactory control of spider mite populations in both vineyards. These results were even obtained on a variety non preferred by phytoseiids (Merlot) and with the continuous presence of anthocorids (vineyard A). After 5 years,A. aberrans was observed in 53% of the plots in vineyard A and in all plots of the other vineyard (B).Results of experiments in whichT. pyri was released were similar to those obtained in the experiments withA. aberrans, but only in the first year of the study. In vineyard A, theT. pyri populations declined dramatically from the second year onwards; the use of a non-preferred variety (Merlot) and the continuous presence of anthocorids seemed the most important factors causing the decline of predatory mite density. In vineyard B,T. pyri was capable of controlling spider mites even in the second year of the experiments. A very low density of macropredators and a preferred grape variety (Raboso) positively affected control. The density ofT. pyri in vineyard B decreased at the end of the second year because of adverse climatic conditions (high temperatures in combination with a low relative humidity). The decrease ofT. pyri allowed the displacement of this species byA. aberrans in all plots of vineyard B. It was also shown that the twoT. pyri strains differed in their efficacy to control spider mites.

The control of eriophyoid mites: state of the art and future challenges

The superfamily of the Eriophyoidea is a large and diverse group of mites, including a number of species of economic importance, mainly on perennial plants in agriculture and forestry. This review focuses on the economic importance and pest status of this group of mites, with emphasis on some genera. The available acaricide portfolio is reviewed and the influence of EU legislation policy on the sustainable control of Eriophyoidea is investigated. Possible generic guidelines for sustainable control and resistance management with special reference to the European situation are discussed. Recent advances in biological and integrated control of eriophyid mite pests and the implementation of these techniques in crops are explored. Furthermore, the relevance of studies on behaviour, epidemiology and diagnostics in general terms and as a strategic necessity is pointed out.

The impact of eriophyoids on crops: recent issues on Aculus schlechtendali, Calepitrimerus vitis and Aculops lycopersici.

The nature of the damage caused by eriophyoid mites and the assessment of yield losses still require detailed studies if appropriate control and risk mitigation strategies are to be planned. The economic importance of eriophyoid mites is increasing worldwide and a lot of species have reached a permanent pest status in certain crops, while others represent a quarantine threat for several countries. Due to their relevant role in Europe and elsewhere, three eriophyoid mites that have been frequently reported in recent research, are here considered as case studies: two of them (the apple rust mite, Aculus schlechtendali, and the grape rust mite, Calepitrimerus vitis) colonise temperate fruits, while one (the tomato russet mite, Aculops lycopersici) affects vegetables. The damage assessment related to the apple rust mite has been evaluated on different apple varieties with implications for pest control. Some factors affecting the spread and economic importance of the grape rust mite have been identified. The complexity and difficulty in controlling the tomato russet mite by chemicals enhances the interest in biological control agents. Considerations on interactions between eriophyoids and host plants (e.g. resistance, varietal susceptibility), on pest management regimes (e.g. impact of fungicides, resistance to acaricides, perspectives on biological control) are presented.

Different colonization patterns of phytophagous and predatory mites (Acari: Tetranychidae, Phytoseiidae) on three grape varieties: a case study

In a vineyard having three varieties of grape (Merlot, Trebbiano and Garganega) differently colonized by two phytoseiid species,Typhlodromus pyri Scheuten andAmblyseius andersoni (Chant), the dynamics of mite populations were monitored over 5 years (1989–1993) in order to study their colonization, interspecific competition and the control of spider mites, i.e.Panonychus ulmi (Koch). These aspects were also investigated by releasingT. pyri, A. andersoni andAmblyseius aberrans (Oudemans) on some of the above varieties. In most of the experimental years (1989–1992), selective pesticides were used in order to allow a successful release of phytoseiids, in particularA. aberrans. The use of non-selective insecticides was re-established during 1993 in order to test its effect on the new mite communities originating from 1989 onwards. In the first years of the experiments an apparent relationship between grape variety and phytoseiid species was observed: in the control plots,A. andersoni occurred on Merlot whereT. pyri was rare, while the latter species was largely dominant overA. andersoni on Trebbiano and Garganega.Panonychus ulmi populations reached moderate levels only on Merlot and in the first part of experiments. The variety-phytoseiid species relationship was temporary as, at the end of experiments,T. pyri was completely dominant on all varieties. This new situation started when prey occurrence and interspecific competition decreased in importance. The moderate success of theT. pyri release on Merlot contrasts with the results of previous experiments. Two factors could be involved in this phenomenon: low interspecific competition by phytoseiids and predation by macropredators.Amblyseius aberrans was able to displaceA. andersoni andT. pyri on grape varieties where the two species were more abundant and reached higher population densities on varieties with pubescent leaf undersurfaces. In the first experimental year, spider mite densities were reduced more effectively inA. aberrans release plots than in the control or inT. pyri release plots. One year later,P. ulmi reached lower levels in the release treatments than in the control.Typhlodromus pyri andA. aberrans persisted in conditions of prey scarcity. The high competitivity ofA. aberrans over the remaining two phytoseiid species constitutes a major factor in selecting predatory species for inoculative releases in vineyards.

Role of the predatory mites Amblyseius aberrans (Oud.), Typhlodromus pyri Scheuten and Amblyseius andersoni (Chant) (Acari, Phytoseiidae) in vineyards

The results of experiments carried out on the releases of phytoseiid mites Amblyseius aberrans (Oud.) and Typhlodromus pyri Scheuten in a vineyard infested by the tetranychid mites Panonychus ulmi (Koch) and Eotetranychus carpini (Oud.) are reported. Increasing densities of predators (10, 25, 40, 50, 100 overwintering females per plant) were released at the beginning of the experiments. Simultaneous releases of the two species were carried out at different ratio to complete previous observations on the competition between the species. The A. aberrans populations controlled the spider mites at low densities independently from the initial release density used. T. pyri seemed more efficient in containing the P. ulmi populations than those of E. carpini. The T. pyri populations declined in the last summer corresponding to high temperatures while the A. aberrans populations seemed not affected by them. In the plots receiving mixed releases of the two species A. aberrans displaced T. pyri within the first year.

Side-effects of pesticides on the predatory bug Orius laevigatus (Heteroptera: Anthocoridae) in the laboratory

Abstract Laboratory trials were carried out in order to test the effects of 29 pesticides on the predatory bug, Orius laevigatus. To evaluate residual contact activity, newly moulted fourth instar nymphs of O. laevigatus were placed on treated Petri dishes and their mortality was checked after 7 days. The fecundity of surviving females was tested for 14 days. Young O. laevigatus adults were fed with eggs of Ephestia kuehniella, treated with the (above-mentioned) pesticides, to assess the effect of pesticides by ingestion. Adult mortality, female fecundity and egg hatching were recorded. Azadirachtin, granulosis virus products, mineral oil, pirimicarb, tebufenozide, clofentezine, hexythiazox and copper oxychloride had no significant effect on the survival and fecundity of O. laevigatus when predators were exposed to pesticide residues by contact or by ingestion. Triflumuron and diflubenzuron appeared to be harmless by contact, but diflubenzuron was slightly toxic when ingested. Buprofezin and teflubenzuron were slightly to moderately toxic, while hexaflumuron, flufenoxuron, and lufenuron showed a marked toxicity by contact as well as by ingestion. A number of organophosphates, endosulfan and deltamethrin were detrimental especially by contact. Imidacloprid was very toxic by contact but only slightly toxic when ingested. Indoxacarb and methoxyfenozide were less toxic than imidacloprid. These findings should be considered when releases of O. laevigatus are used in greenhouses or on outdoor crops.