Gavino Delrio

Control of Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae) in greenhouse tomato crops using the mating disruption technique.

The effectiveness of mating disruption to control the tomato leafminer, Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae), in greenhouse tomato crops was evaluated in four trials carried out in winter–spring and summer–winter growing seasons in Southwestern Sardinia (Italy). Pheromone dispensers loaded with 60 mg of the natural blend of the major and minor sex pheromone component (rate 90 : 10) were applied in disrupted greenhouses at a rate of 1000/ha (60 g of active ingredient/ha). Male captures in monitoring pheromone traps, percentage of tomato plants infested by T. absoluta and damage on leaves and fruits were monitored weekly and compared in disrupted and untreated (control) greenhouses. In greenhouses disrupted with 1000 dispensers/ha, a reduction of 93–97% in male trap captures was observed, compared with control. Leaf damage was significantly lower in greenhouses disrupted with 1000 dispensers/ha than in control ones, with a reduction of infestation throughout the growing season ranging from 57% to 85%. Pheromone dispensers applied at the density of 1000/ha significantly reduced the percentage of damaged fruits by 62–89%. In control greenhouses, the highest damage on leaves and fruits was generally observed in edge plants, while leaf and fruit infestation was uniformly distributed in pheromone‐treated greenhouses, indicating an even distribution of the pheromone cloud inside the greenhouse. Mating disruption showed to be an efficient strategy to control in greenhouse the tomato leafminer and can be included in the overall tomato integrated pest management programs.

Larval habitats and seasonal abundance of Culicoides biting midges found in association with sheep in northern Sardinia, Italy.

Between January 2005 and December 2006, the larval habitats and seasonal abundances of 21 species of Culicoides (Diptera: Ceratopogonidae) found in association with livestock on a farm in northern Sardinia were studied. Culicoides were collected using two light traps (one placed in a sheep shed and the other near water ponds) and reared from mud collected in and along the margins of a small and a large water pond. The mammalophilic Culicoides imicola Kieffer and Culicoides newsteadi Austen were the most prevalent (>95%) of 20 species in the sheep shed, whereas the ornithophilic Culicoides univittatus Vimmer, Culicoides sahariensis Kieffer, Culicoides festivipennis Kieffer, Culicoides circumscriptus Kieffer and Culicoides cataneii Clastrier were most abundant in the traps set at the ponds (73%) and in 16 species of Culicoides reared from laboratory‐maintained mud samples retrieved from three microhabitats (a non‐vegetated pond shoreline, 20 cm above a pond shoreline, the shoreline of a secondary, permanently inundated, grass‐covered pool). The species reared most abundantly from along the pond shoreline were C. festivipennis, C. circumscriptus and C. sahariensis, whereas those most prevalent at the grassed pool were C. cataneii and C. festivipennis. C. imicola was found to breed preferentially in mud 20 cm above the pond shoreline, whereas C. newsteadi was restricted almost entirely to the grassed pool, which had a high organic matter content. Using the light trap and adult emergence data, the seasonal abundance patterns of the eight species of Culicoides were determined. In general, there was good correspondence between light trap catches and emergence trends. Well‐defined emergence peaks indicate four or five generations for C. festivipennis and C. circumscriptus and three generations for C. cataneii, C. newsteadi and Culicoides jumineri Callot & Kremer. The emergence trends for C. imicola and C. sahariensis were unimodal, but, because they stretched over several months, indicated that a number of overlapping generations had occurred. Adults of C. imicola were reared and captured only sporadically in the first half of the year, gradually building to a peak in autumn. Conversely, C. newsteadi was reared throughout the year and displayed three clearly defined peaks (in winter, spring and autumn); captures of C. newsteadi in the light traps peaked in May–June and again to a lesser extent in autumn. In Sardinia the late seasonal peak in the abundance of C. imicola occurs in synchrony with outbreaks of bluetongue (BT) in sheep, which is consistent with earlier findings elsewhere in the Mediterranean basin and in Africa that it is the principal vector of bluetongue virus (BTV). Although the status of C. newsteadi as a vector of BTV is not known, its low‐level presence in winter and heightened abundances in spring may provide a pathway along which the virus can overwinter.

Lethal and sublethal effects of Brevibacillus laterosporus on the housefly ( Musca domestica )

Sporulated cultures of an isolate of the entomopathogenic bacterium Brevibacillus laterosporus (Laubach) from soil in Sardinia (Italy) were highly toxic by ingestion to both adults and juveniles of the housefly, Musca domestica L. (Diptera: Muscidae). Toxicity was associated with spores as the culture supernatant was not toxic and no parasporal inclusions were observed. The level of toxicity varied with the concentration of spores, the time of exposure to the treated diet, and the stage of insect development. Comparative LC50 values were 0.72 × 108 and 1.75 × 108 spores per gram of diet for 1st and 2nd instar larvae, respectively, and 3.84 × 108 spores per gram for adults. A significant increase in larval development time and reductions in pupal weight and emergence rate were observed when larvae were fed on diets containing sublethal concentrations of spores. Adults surviving after feeding on a sublethal diet showed a significant reduction in fecundity and longevity. Similarly, adults from treated larvae exhibited a lower fecundity, although their longevity was not influenced. A relationship between pupal weight and adult fecundity was found. Pupal stage duration and egg eclosion were not significantly affected.

Spatial distribution and sequential sampling plans for Tuta absoluta (Lepidoptera: Gelechiidae) in greenhouse tomato crops

BACKGROUND The within- and between-plant distribution of the tomato leafminer, Tuta absoluta (Meyrick), was investigated in order to define action thresholds based on leaf infestation and to propose enumerative and binomial sequential sampling plans for pest management applications in protected crops. RESULTS The pest spatial distribution was aggregated between plants, and median leaves were the most suitable sample to evaluate the pest density. Action thresholds of 36 and 48%, 43 and 56% and 60 and 73% infested leaves, corresponding to economic thresholds of 1 and 3% damaged fruits, were defined for tomato cultivars with big, medium and small fruits respectively. Greens method was a more suitable enumerative sampling plan as it required a lower sampling effort. Binomial sampling plans needed lower average sample sizes than enumerative plans to make a treatment decision, with probabilities of error of <0.10. CONCLUSIONS The enumerative sampling plan required 87 or 343 leaves to estimate the population density in extensive or intensive ecological studies respectively. Binomial plans would be more practical and efficient for control purposes, needing average sample sizes of 17, 20 and 14 leaves to take a pest management decision in order to avoid fruit damage higher than 1% in cultivars with big, medium and small fruits respectively.

Bluetongue outbreaks: Looking for effective control strategies against Culicoides vectors.

Several arthropod-borne diseases are now rising with increasing impact and risks for public health, due to environmental changes and resistance to pesticides currently marketed. In addition to community surveillance programs and a careful management of herds, a next-generation of effective products is urgently needed to control the spread of these diseases, with special reference to arboviral ones. Natural product research can afford alternative solutions. Recently, a re-emerging of bluetongue disease is ongoing in Italy. Bluetongue is a viral disease that affects ruminants and is spread through the bite of bloodsucking insects, especially Culicoides species. In this review, we focused on the importance of vector control programs for prevention or bluetongue outbreaks, outlining the lack of effective tools in the fight against Culicoides vectors. Then, we analyzed a field case study in Sardinia (Italy) concerning the utilization of the neem cake (Azadirachta indica), to control young instar populations of Culicoides biting midges, the vectors of bluetongue virus. Neem cake is a cheap and eco-friendly by-product obtained from the extraction of neem oil. Overall, we propose that the employ of neem extraction by-products as aqueous formulations in muddy sites close to livestock grazing areas may represent an effective tool in the fight against the spread of bluetongue virus in the Mediterranean areas.

Seasonal phenology of Tuta absoluta (Lepidoptera: Gelechiidae) in protected and open-field crops under Mediterranean climatic conditions

The population structure and dynamics of the tomato leafminer Tuta absoluta were investigated in a protected tomato crop and on potato and tomato crops and Solanum nigrum plants under open-field Mediterranean climatic conditions (Sardinia) by captures in pheromone-baited traps and visual inspection of host plants. In the greenhouse crop, male captures and leaf infestation were low in winter and increased steadily in spring up to 797.3 males/trap/week and 6.4 mines/leaf, respectively. Under open-field conditions, males were captured all year round with a peak in early September, concurrently with highest mean daily temperatures. Pest density in potato crops was very low (<0.3 mines/leaf), as well as on S. nigrum (0.16 mines/leaf). Conversely, high pest infestation was observed in tomato leaves (3.8 mines/leaf) and fruits (27% damaged fruits). Eggs, larvae and adults were detected over two consecutive winters, indicating that T. absoluta can develop continuously over the year under natural conditions. Parasitoids were recorded throughout the survey at low rates (≤16.1%). The most active beneficials were Necremnus tutae and Neochrysocharis formosa in protected and open-field crops, respectively. The tomato leafminer completed 6 generations in the greenhouse tomato crop during the winter-spring growing season, whereas in open-field crops the pest completed two generations on winter potato and 4-5 in spring-summer tomato. The degree-day model based on minimum and maximum temperatures reliably described the population dynamics in the protected crop, and estimated the completion of 7.4 generations per year under open-field Mediterranean conditions.

An Updated Checklist of the Culicoides Latreille (Diptera: Ceratopogonidae) of Sardinia (Italy), and Seasonality in Proven and Potential Vectors for Bluetongue Virus (BTV)

Abstract. Using suction light traps biting midges of the genus Culicoides Latreille (Diptera: Ceratopogonidae) were collected between 2004 and 2006 on nine cattle and/or sheep farms distributed throughout the length of the island of Sardinia (Italy). A total of 42,664 adult midges (36,655 females, 6,009 males) were collected during 287 trapping nights; 41 species of Culicoides were identified, of which 16 are new records for Sardinia. Eight of these, i.e., Culicoides derisor Callot and Kremer, Culicoides duddingstoni Kettle and Lawson, Culicoides kingi Austen, Culicoides paradisionensis Boorman, Culicoides santonicus Callot, Kremer, Rault and Bach, Culicoides subfagineus Delécolle and Ortega, Culicoides submaritimus Dzhafarov, and Culicoides truncorum Edwards, are also new to the biting midge fauna of Italy. The six most-abundant species captured were Culicoides newsteadi Austen (21.7%), Culicoides univitattus Vimmer (12.6%), Culicoides circumscriptus Kieffer (12.5%), Culicoides paolae Boorman (12.0%), Culicoides obsoletus (Meigen), Culicoides scoticus Downes and Kettle (10.6%) and Culicoides imicola Kieffer (10.1%); the last-mentioned species is the principal vector for bluetongue virus (BTV) affecting sheep in the Mediterranean basin. Bar charts depicting the seasonality at three collecting sites of six proven or potential vectors for BTV, and belonging mostly to the obsoletus and pulicaris species complexes, are presented and discussed. Finally, an updated checklist is provided for the 45 species of Culicoides now known to occur on Sardinia and includes corrections on misidentifications made in an earlier checklist.