Vincenzo Candido

Greenhouse soil solarization: effect on weeds, nematodes and yield of tomato and melon

Phase-out of methyl bromide and health concerns related to the use of pesticides are increasing the interest in alternative control strategies. Soil solarization is an effective, safe and cheap technique for the control of soil-borne pathogens and weeds. However, knowledge of the long-term effects of solarization, as well as of repeated solarization cycles, is scarce. Such knowledge should in particular help to minimize the number of solarization treatments. Therefore, we tested the residual effect of a single solarization treatment and the effects of two or three solarization cycles on root-knot nematodes, weeds and crop yield for three years on greenhouse-grown tomato and melon. Soil solarization was applied for either one, two or three consecutive years on a soil infested by the root-knot nematode Meloidogyne javanica and many annual and perennial weed species. An untreated soil was used as a control. At the end of each crop cycle yield parameters were recorded, weeds were identified and counted, and nematode infestation was evaluated. Our results show that a single solarization treatment significantly increased yields by +116%, and strongly reduced nematode infestation of −99% of infested plants and of −98% of the root gall index in the following melon crop. It also suppressed annual weed emergence three years later. Plant yields from two- and three-year solarized soil were always higher than nonsolarized control: +284% and +263%, respectively, for tomato, and +162% and +368%, respectively, for melon. Further, two- and three-year solarization treatments almost completely suppressed the infestation of the M. javanica nematode in tomato, and reduced the nematode effect in melon by −86% and −79%, respectively. Repeated solarization treatments also resulted in a high reduction of emergence of most weed species in all crop cycles. A single soil solarization treatment was shown to be effective for a long-term sustainable management of weeds, whereas the time-limited effectiveness against root-knot nematodes can be enhanced through two- or three-year repeated treatments.

Effect of irrigation regimes and artificial mycorrhization on insect pest infestations and yield in tomato crop

A 2-year field experiment was carried out to test the effect of root symbionts treatments in combination with different watering levels on tomato yield and pest infestation rates. A split-plot experimental design was followed, where the main treatments were three irrigation regimes, and the subplot factor was the mycorrhizal treatment (two mycorrhizal treatments [M1 and M2] and the control). The M1 treatment consisted in the use of a commercial preparation (Micosat F; CCS Aosta, Italy) containing a mixture of vesicular-arbuscular mycorrhizae (VAM), bacteria of the rhizosphere and saprophytic fungi, while M2 treatment used only arbuscular mycorrhizal fungi. Insect pests sampled in the field during the 2 years of experiment were all sap-feeders (Trialeurodes vaporariorum, Macrosiphum euphorbiae, Frankliniella occidentalis and an unidentified species of leafhopper). Results did not show any impact of root symbionts on pests, whereas water deficit significantly reduced plant infestation rates. Both mycorrhization treatments and water supply resulted in a significantly positive effect on crop yield.

Effects of Irrigation-Fertilization and Irrigation-Mycorrhization on the Alimentary and Nutraceutical Properties of Tomatoes

Tomato, a key vegetable in the Italian Mediterranean diet, has recently gaining been attention in relation to the prevention of some human diseases. This interest is due to the presence of carotenoids and particularly lycopene, which is an unsaturated alkylic compound, that appears to be an active compound in the prevention of cancer, cardiovascular risk and in slowing down cellular aging, owing to its high antioxidant and antiradical power (Gerster 1997; Giovannucci et al. 1995). Lycopene is found in fresh, red-ripe tomatoes as all-trans (79-91 %) and cis(9-21%) isomers (Boileau et al., 2002; Shi et al., 1999; Stahh & Sies, 1992).

Soil Solarization and Sustainable Agriculture

Pesticide treatments provide an effective control of soilborne pests in vegetable and fruit crops, but their toxicity to animals and people and residual toxicity in plants and soil, and high cost make their use hazardous and economically inconvenient. Moreover, actual environmental legislation is imposing severe restrictions on the use or the total withdrawal of most soil-applied pesticides. Therefore, an increasing emphasis has been placed on the use of nonchemical or pesticide-reduced control methods. Soil solarization is a nonpesticidal technique which kills a wide range of soil pathogens, nematodes, and weed seed and seedlings through the high soil temperatures raised by placing plastic sheets on moist soil during periods of high ambient temperature. Direct thermal inactivation of target organisms was found to be the most important mechanism of solarization biocidal effect, contributed also by a heat-induced release of toxic volatile compounds and a shift of soil microflora to microorganisms antagonist of plant pathogens. Soil temperature and moisture are critical variables in solarization thermal effect, though the role of plastic film is also fundamental for the solarizing process, as it should increase soil temperature by allowing the passage of solar radiation while reducing energetic radiative and convective losses. Best solarizing properties were shown by low-density or vynilacetate-coextruded polyethylene formulations, but a wide range of plastic materials were documented as also suitable to soil solarization. Solar heating was normally reported to improve soil structure and increase soil content of soluble nutrients, particularly dissolved organic matter, inorganic nitrogen forms, and available cations, and shift composition and richness of soil microbial communities, with a marked increase of plant growth beneficial, plant pathogen antagonistic or root quick recolonizer microorganisms. As a consequence of these effects, soil solarization was largely documented to increase plant growth and crop yield and quality along more than two crop cycles. Most important fungal plant pathogenic species were found strongly suppressed by the solarizing treatment, as several studies documented an almost complete eradication of economically relevant pathogens, such as Fusarium spp., Phytophthora spp., Pythium spp., Sclerotium spp., Verticillium spp., and their related diseases in many vegetable and fruit crops and different experimental conditions. Beneficial effects on fungal pathogens were stated to commonly last for about two growing seasons and also longer. Soil solarization demonstrated to be effective for the control of bacterial diseases caused by Agrobacterium spp., Clavibacter michiganensis, and Erwinia amylovora, but failed to reduce incidence of tomato diseases caused by Pseudomonas solanacearum. Solarization was generally found less effective on phytoparasitic nematodes than on other organisms, due to their quicker soil recolonization compared to fungal pathogens and weeds, but field and greenhouse studies documented consistent reductions of root-knot severity and population densities of root-knot nematodes, Meloidogyne spp., as well as a satisfactory control of cyst nematode species, such as Globodera rostochiensis and Heterodera carotae, and bulb nematode Ditylenchus dipsaci. Weeds were variously affected by solar heating, as annual species were generally found almost completely suppressed and perennial species more difficult to control, due to the occurrence deep propagules not exposed to lethal temperature. Residual effect of solarization on weeds was found much more pronounced than on nematodes and most fungal pathogens. Soil solarization may be a perfect fit for all situations in which use of pesticides is restricted or completely banned, such as in organic production, or in farms located next to urban areas, or specialty crops with few labeled pesticides. Advantages of solarization also include economic convenience, as demonstrated by many comparative benefit/cost analyses, ease of use by growers, adaptability to many cropping systems, and a full integration with other control tools, which makes this technique perfectly compatible with principles of integrated pest management required by sustainable agriculture.

Evaluation of Native Grasses for Sustainable Turfgrass in the Bioclimatic Mediterranean Region

This study reports the results of a research project (Mi.T.E.A.Med) funded by the Italian Ministry of Agriculture. The research was organised in two phases: the first one involved the screening of the study area (Southern Italy) to find suitable turfgrass species and the second one focused on ex situ cultivation to test the ecotypes with salinity resistance. During the first step of the research, 11 sites from 6 regions of Southern and Central Italy were identified. In these sites, 24 ecotypes of Cynodon dactylon (L.) Pers. were collected and their habitus, phenology, and some biometric parameters have been determined. During the 2 years of research, both botanic and agronomic characterisation of the collected C. dactylon ecotypes was carried out. Some native accessions showed a behaviour similar to commercial cultivars, while an ecotype from the Abruzzo Region showed better results compared to the commercial cultivars for several quality indices. The results of this project showed that Mediterranean-adapted native grass species (e.g. Cynodon dactylon (L.) Pers.) are worth investigating for turfgrass, making for their performance and low resource requirement (especially water). This species can be used as promising alternatives to conventional non-native turfgrasses.

Correction to: Nematicidal potential of Taraxacum officinale

The original publication of this paper contains a mistake. Data on Table 1 under TR and TL column have been interchanged: that is compounds 1-12 and their amounts refer to TL; compounds 1-8 and related amounts refer to TR (see Fig. 1).

Seed-propagated Muscari comosum (L.) Mill.: Effects of sowing date and growing conditions

Abstract Muscari comosum is a widespread Mediterranean species with a long use as food. The edible part is the bitter bulb that has to be cooked. The increasing value of bulbs, also due to a renewed cultural interest toward traditional foods and their benefits for health, claims to enhance the agricultural production. Surprisingly, no agronomic studies about the best practice of propagation exist. We tested whether and how germination rate and weight and size of bulbs, after one growing season, were affected by sowing date (autumn–spring), growing condition (greenhouse, shaded greenhouse and open field), and container’s volume. Results showed that the best-sowing period ranges between September and January; following this period there is a huge decrease in germination rate. The time of seedling emergence was higher in open field than in protected environment. The longer interval of growing was observed with the sowing of October that produced heavier and larger bulbs. The best combination to obtain larger bulbs is sowing in October under greenhouse. However, under shaded conditions it was possible to obtain satisfactory results even with medium-late sowing (December and January). Containers with higher volume generally performed better. We conclude that mass propagation of M. comosum could be efficiently performed for agronomic purposes using nurseries. In fact, due to the high rate of germination and to the ease of obtaining the seeds from wild populations or from cultivations, there is the possibility to produce large quantities of bulbs to develop new crops of this traditional food.