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Acta Horticulturae
No full textThe citrus-growing area in Panama has increased considerably in recent years. Disease problems are frequently observed in orchards, but in most cases their etiology is unknown, complicating the design of effective control strategies. A survey was initiated in 2010, visiting 50 orchards in different regions of the country. In each orchard, symptoms were characterized and samples were collected from the affected organs. Isolations from symptomatic tissues were made on general and selective media and then the fungal isolates were transferred to PDA and V8-juice agar for morphological identification. Molecular identification was carried out on representative isolates by amplifying and sequencing the internal transcribed spacer (ITS) region. Mycosphaerella citri, the causal agent of citrus greasy spot, was isolated from necrotic pustules on the leaves of trees showing chlorosis, and premature defoliation, which were observed in 75% of the surveyed orchards. This disease was found to be the prevalent fungal disease of citrus in Panama. Colletotrichum acutatum was consistently isolated from petals and from fruits that dropped prematurely from lime and sweet orange orchards and pathogenicity tests identified the isolates as the causal agent of Key lime anthracnose disease. Furthermore, melanose on sweet orange leaves and fruits was associated with Phomopsis sp
Acta Horticulturae
No full textThe performance of 'Maltaise demi-sanguine' sweet orange infected with Citrus exocortis viroid (CEVd) and Hop stunt viroid (HSVd, Variant CVIIb) was evaluated on eight different rootstocks (sour orange, 'Carrizo' citrange, volkamer lemon, 'Cleopatra' mandarin, 'Swingle' citrumelo, 'Rangpur' lime, alemow and trifoliate orange) at the INRAT station in El Gobba, Cap Bon region, Tunisia. The trees were planted in 2005 and fruit production and fruit quality and size were evaluated every year since 2007. For non-inoculated trees, the trunk circumference was larger for plants grown on citrumelo, volkamer lemon and 'Carrizo' citrange than for those grown on sour orange. Trees on volkamer lemon also had a larger canopy volume. Infection with HSVd-CVIIb caused severe stunting and low production on trees grafted on alemow, and to a lesser extent reduced trunk diameter and production of trees on 'Swingle' citrumelo, whereas inoculation with CEVd or HSVd had little effect on the growth and yield of trees propagated on the other rootstocks. The only effect of HSV-CVIIb infection on fruit quality consisted of increased juice weight in plants propagated on 'Rangpur' lime and acidity in plants on volkamer lemon and decreased total soluble solids in plants on sour orange
Medfly Ceratitis capitata as Potential Vector for Fire Blight Pathogen Erwinia amylovora: Survival and Transmission
Get PDFMonitoring the ability of bacterial plant pathogens to survive in insects is required for elucidating unknown aspects of their epidemiology and for designing appropriate control strategies. Erwinia amylovora is a plant pathogenic bacterium that causes fire blight, a devastating disease in apple and pear commercial orchards. Studies on fire blight spread by insects have mainly focused on pollinating agents, such as honeybees. However, the Mediterranean fruit fly (medfly) Ceratitis capitata (Diptera: Tephritidae), one of the most damaging fruit pests worldwide, is also common in pome fruit orchards. The main objective of the study was to investigate whether E. amylovora can survive and be transmitted by the medfly. Our experimental results show: i) E. amylovora can survive for at least 8 days inside the digestive tract of the medfly and until 28 days on its external surface, and ii) medflies are able to transmit the bacteria from inoculated apples to both detached shoots and pear plants, being the pathogen recovered from lesions in both cases. This is the first report on E. amylovora internalization and survival in/on C. capitata, as well as the experimental transmission of the fire blight pathogen by this insect. Our results suggest that medfly can act as a potential vector for E. amylovora, and expand our knowledge on the possible role of these and other insects in its life cycle
Prospects for predatory mirid bugs as biocontrol agents of aphids in sweet peppers
No full textIn recent years, biological control strategies to control many major horticultural pests have been successfully implemented in the Eastern Mediterranean basin. However, the management of some pests, such as aphids in sweet pepper crops, can still be improved. The goal of this study was to examine the potential of the omnivorous predatory mirids Nesidiocoris tenuis, Macrolophus pygmaeus, and Dicyphus maroccanus as biocontrol agents of aphids in sweet pepper crops. First, the capacity to detect Myzus persicae-infested and un-infested plants was studied in a Y-tube olfactometer. Females of the three species of predatory mirids were strongly attracted to the odor of infested M. persicae plants. Second, the prey suitability of young and mature nymphs of M. persicae for these three mirid species was studied. The three species actively preyed on M. persicae, although D. maroccanus resulted the most voracious species preying both young and mature nymphs. Finally, the capacity of the three omnivorous predators to reduce M. persicae in heavily infested plants was determined in semi-field conditions. The three species of mirids could reproduce on aphids and establish on sweet pepper plants. Mirids significantly reduced the number of M. persicae per leaf, reaching levels of aphid reduction close to 100 % when compared to the untreated control. These results suggest that mirids might play a major role in aphid management in sweet peppers. The potential implementation methods of predatory mirids for the biological control in sweet peppers are discussed
Acta Horticulturae
No full textThe citrus nursery tree certification program in Spain includes four blocks of trees: 1) The protected foundation block, maintained at IVIA, that includes healthy plants of local and foreign varieties recovered by shoot-tip grafting in vitro. Plants are grown in containers inside insect-proof screenhouses. 2) Foundation blocks propagated with budwood from the protected foundation block and also grown inside screenhouses. They belong to individual nurseries or nursery groups. 3) Budwood increase blocks, maintained inside screen-or greenhouses at each nursery, include plants propagated directly from foundation trees to increase the number of buds for propagation of certified trees. 4) Certified nursery trees propagated with budwood from the increase blocks and grown in screen-or greenhouses or in the open field. Plants of each block are periodically indexed for different pathogens according to the regulations. The program started in 1979 when the first healthy plants were released to the nurseries and the first certified plants arrived to growers in 1982. Since then, more than 142 million certified plants of 103 varieties have been propagated, with sweet oranges representing 51%, clementines 28%, other mandarins 14%, lemons 6% and grapefruits 1%. Presently Carrizo citrange is used as rootstock for 59% of the nursery plants and Citrus macrophylla for 19%. A total of 40 nurseries, grouped in 7 foundation blocks, are presently operating. Under this program practically all the Spanish citrus industry has been renewed with healthy plants. Today, traditional graft transmissible pathogens are not a problem for our citrus industry
Pezothrips kellyanus (Thysanoptera: Thripidae) nymphs on orange fruit: importance of the second generation for its management
Get PDFKelly's citrus thrips Pezothrips kellyanus (Bagnall) (Thysanoptera: Thripidae) is a new pest of oranges in New Zealand, southern Australia, and the Mediterranean Basin. The nymphs of this thrips can damage the fruit from petal fall up to 6 wk later. Because there is a lack of information on its management, the aims of this study were to determine the number of generations occurring on the fruit and the efficacy of 3 insecticides (chlorpyrifos, spinosad, and spirotetramat) to control this pest. Chlorpyrifos and spinosad displayed a high efficacy against nymphs and reduced significantly the percentage of damaged fruit when a single generation of P. kellyanus attacked the fruit. However, these insecticides did not prevent development of a subsequent generation of P. kellyanus. The percentage of damaged fruit was higher when the 2nd generation was present. Spirotetramat did not display a knockdown effect, and its efficacy was less than that of chlorpyrifos and spinosad. Similar to these insecticides, spirotetramat did not prevent the attack of a 2nd generation when it occurred. Additionally, we analyzed the side effects of these treatments on predatory mites. Spinosad and spirotetramat negatively affected these beneficial species
Drift reduction of low drift nozzles in spraying citrus orchards
Get PDFDrift is especially critical when spraying fruit, vine and citrus orchards where pesticides are intensively used. In this context, cone low drift nozzles (LDN) intended for spraying tree crops, have been evaluated relating to cone standard nozzles (STN) in laboratory and deciduous fruit orchards (Van de Zande et al. 2012); (Planas et al., 2013)
Efficacy of standard and low drift nozzles for insecticide applications against Aonidiella aurantii (Maskell) in citrus
Get PDFThe use of low-drift nozzles (LDN) is the cheapest and easiest method to reduce drift. However, use of LDN may affect the efficacy of plant protection products for controlling targeted pests. Studies characterizing LDN efficacy in apples have been described (Heinkel et al., 2000; Frießleben, 2004; Lešnik, 2005; McArtney & Obermiller, 2008), but none have been published in citrus. This is significant because in contrast to apples, citrus trees have a globular shape and a very dense canopy. For these reasons, the aim of this work was to investigate the efficacy of insecticide applied using LDN or standard cone nozzles for the control of California red scale (CRS) (Aonidiella aurantii (Maskell) (Hemiptera: Diaspididae)) in citrus
Effect of micellized natural (D-alpha-tocopherol) vs. synthetic (DL-alpha-tocopheryl acetate) vitamin E supplementation given to turkeys on oxidative status and breast meat quality characteristics
No full textThis study evaluates the effect of vitamin E supplementation source (micellized natural vs. the synthetic form) and dosage (40, 80, or 120 mg/kg) on alpha-tocopherol concentration in plasma and muscle, antioxidant capacity, and breast meat quality in turkeys. Three hundred female turkeys were randomly selected at an average live weight 63.2 g +/- 0.5 and distributed into 7 groups. One group (control) was fed a standard diet without vitamin E supplementation and the other 6 were given mixed diets supplemented with the natural (d-alpha-tocopherol) or synthetic (dl-alpha-tocopheryl acetate) form of vitamin E in 3 dosages (40, 80, or 120 mg/kg). Following 11 wk feeding, results showed that performance parameters were not modified either by source or dosage of vitamin E supplementation to the turkeys. Plasma and muscle alpha-tocopherol at d 9 of refrigerated storage were higher when turkeys were supplemented with the natural form at higher doses. Losses in the concentration of a-tocopherol in meat between the beginning and the end of the 9 d refrigerated storage were greater in the groups supplemented with the synthetic form of vitamin E compared to those receiving the natural supplementation. The relationship between plasma a-tocopherol and the Trolox equivalent antioxidant capacity followed a different trend depending on the vitamin E source. Intramuscular fat was not significantly affected by the vitamin E source supplementation; however the slope of the linear regression equation was lower for the natural form than for the synthetic form. Turkeys given the natural form had higher C18:1n-9 but lower C15:1, C17:1, C20:5n-3, and C22:6n-3 in breast muscle. Meat samples from turkeys supplemented with natural vitamin E had higher deoxymyoglobin at d 3, 6, and 9 and lower metmyoglobin at d 9 of refrigerated storage than those receiving the synthetic form. Dietary supplementation with medium doses (80 mg/kg) micellized d-alpha-tocopherol is an interesting feeding strategy for ensuring antioxidant status and improving meat quality
Acta Horticulturae
No full textTetraploidy is a spontaneous phenomenon in citrus that leads to some anatomical differences between tetraploid (4x) and the corresponding diploid (2x) citrus seedlings, and interesting phenotypes like dwarfism and tolerance to abiotic constraints. The choice of a suitable rootstock is often very restricted by a combination of biotic and abiotic stresses. In this work we investigated the behavior of 4x and 2x 'Carrizo' citrange (Citrus sinensis x Poncirus trifoliata) subjected to the main abiotic stresses that threat the Spanish citrus industry. Seedlings were exposed to salinity, drought and iron deficiency, and physiological parameters were measured. Results suggest that 4x plants stressed by drought were less affected than 2x. Under salt stress no difference was found in leaf ion content, neither in gas exchange parameters, but leaf burn was less severe in 4x than in 2x. Concerning iron deficiency, a better tolerance of 4x compared to 2x was supported by higher Ferricchelate reductase activity, SPAD index and chlorophyll fluorescence. These preliminary results suggest that 4x 'Carrizo' citrange could be a promising rootstock, having nearly the same performance than the original 2x, but producing smaller trees more tolerant to abiotic stresses