Distribution and prevalence of nematodes (Scutellonema bradys and Meloidogyne spp.) on marketed yam (Dioscorea spp.) in West Africa

The distribution, population density and incidence of plant parasitic nematodes and associated damage to yam (Dioscorea spp.) tubers obtained from market stalls in the West African countries of Benin, Burkina Faso, Côte d’Ivoire, Ghana, Mali, Nigeria and Togo was determined during the tuber storage periods in 2002 and 2003. A total of 527 yam tuber samples, exhibiting typical nematode (Scutellonema bradys) damage symptoms, were collected and assessed for S. bradys densities. In addition 25,318 tubers on sale in markets were assessed for visual symptoms (except in Nigeria) of nematode damage (S. bradys and Meloidogyne spp.). S. bradys was present in all countries assessed, with greatest (P ≤ 0.05) mean population densities occurring in tubers in Benin (397 g⁻¹), followed by Nigeria (248 g⁻¹) and lowest in Togo (28 g⁻¹). When analysed by agroecological zone, the greatest (P ≤ 0.05) mean S. bradys density was observed in the mid altitude savannah (890 g⁻¹), followed by the southern guinea savannah (488 g⁻¹). S. bradys occurred in lower (P ≤ 0.05) densities on Dioscorea alata (57 g⁻¹) than other yam species, while Dioscorea rotundata was the most abundant yam species encountered. There was considerable variation in S. bradys density between cultivars within country and in some cases between countries. From some cultivars no S. bradys were recovered, even though they presented symptoms of damage. Tubers from Ghana had the greatest (P ≤ 0.05) proportion of tubers visually affected by S. bradys (7.53%), when analysed across yam species and Mali the least (0.28%), while the highest proportion of galled tubers (due to Meloidogyne spp.) was observed in Mali (14.4%) on D. rotundata (19.6%). S. bradys infection, based on visible symptoms, was more evident on D. rotundata (3.8%) than D. alata (0.6%), although 5.18% of yams in the group comprising the unidentified yam species had the greatest mean proportion of visually affected tubers. On market stalls, D. alata (4.73%) and D. rotundata (3.35%) were most affected by visible galling due to Meloidogyne spp.     

Amendment of soil with African marigold and sunn hemp for management of Meloidogyne incognita in selected legumes

Field experiments were conducted in 2008 and 2009 in the tropical rainforest zone of Nigeria to investigate the effects of amendment of soil with seedlings of African marigold (Tagetes erecta) and sunn hemp (Crotalaria juncea) incorporated singly in plots on Meloidogyne incognita and yield of cowpea and soybean. The experimental field, which was naturally free of plant-parasitic nematodes, was inoculated with chopped roots of M. incognita race 2-infected Celosia argentea roots and planted to tomato to increase M. incognita population at the site.Eight week-old marigold seedlings were incorporated in cowpea or soybean field and eight week-old sunn hemp seedlings were also incorporated in cowpea or soybean field. At the ends of the experiments, M. incognita population densities were significantly higher in control plots than those of the plots amended with marigold or sunn hemp with correspondingly higher grain yield in the amended plots in both cowpea and soybean fields in both years. A significantly higher population of the nematode and consequently, lower yield was associated with cultivar Ife Brown than cultivar Ife Bimpe of cowpea for each treatment whereas in soybean cultivars, the pattern was not definite. Also twelve seedlings of marigold or sunn hemp per plot incorporated into the soil produced significantly higher grain yield in cultivar Ife Brown of cowpea and cultivar TGX 1440 of soybean compared to six seedlings per plot. The results of this study suggest that incorporating marigold or sunn hemp in M. incognita-infected cowpea or soybean field has potentials to suppress M. incognita population and reduce nematode damage on yield of the associated leguminous crops.     

Nutritional assessment of yam (Dioscorea alata) tubers

The nutrient and antinutrient components of tubers from seven cultivars ofDioscorea alata were determined. The average crude protein content ofD. alata tubers was 7.4%. Starch (75.6–84.3%) was the predominant fraction of the tuber dry matter. Significant differences in crude protein and starch contents were observed among cultivars. Vitamin C content of the yam tubers ranged from 13.0 to 24.7 mg/100 g fresh weight. The results showed yams to be reasonably good sources of minerals. Phytic acid contents of the yams were low, with values ranging from 58.6 to 198.0 mg/100 g dry matter. Total oxalate levels in yam tubers were found to be in the range of 486–781 mg/100 g dry matter, but may not constitute a nutritional concern since 50–75% of the oxalates were in the water-soluble form. The overall results are suggestive of the nutritional superiority of yams compared to other tropical root crops.     

Interactive effects of Meloidogyne incognita race 2, Bradyrhizobium japonicum and crude extracts of Cucumis myriocarpus fruit on Vigna unguiculata

Crude extracts of wild cucumber (Cucumis myriocarpus) fruit, without information on their effects on nodulation, had been touted as having potential as a nematicide and a fertiliser in low-input cowpea (Vigna unguiculata) production systems. Interactive effects of the southern root-knot nematode (Meloidogyne incognita), Bradyrhizobium japonicum and crude extracts of wild cucumber (C. myriocarpus) fruit on each other and growth of cowpea variety Eureka were investigated in a 23 factorial experiment. At harvest, 70 days after initiating the treatments, significant (P ≤ 0.05) first order interactions between any two of the three main factors on variables measured were observed, with interactive effects being either stimulatory or inhibitory. Crude extracts of C. myriocarpus fruit were basically suppressive on nematode numbers but stimulated nodulation and growth of cowpea. Consequently, the material is suitable for use in managing population densities of M. incognita on cowpea production in low-input cowpea production systems.     

Root-knot and reniform nematode reproduction on kenaf and sunn hemp compared with that on nematode resistant and susceptible cotton

Kenaf (Hibiscus cannabinus L.) and sunn hemp (Crotalaria juncea L.) are industrial fiber crops that are being grown increasingly in areas where cotton (Gossypium hirsutum L.) is the major crop. The nematodes causing most cotton yield losses in the USA are the southern root-knot nematode, Meloidogyne incognita (Kofoid and White) Chitwood, and the reniform nematode, Rotylenchulus reniformis Linford and Oliveira. For nematode management, knowledge about the comparative effects of kenaf, sunn hemp, and cotton on nematode population densities in the soil is important. The objective of this study was to clarify the host status of kenaf and sunn hemp to M. incognita and R. reniformis by directly comparing reproduction of each nematode on each crop with the same nematode's reproduction on nematode-resistant and nematode-susceptible cotton. Comparisons were made in six experiments under growth chamber, microplot, and field conditions. The results showed that sunn hemp is resistant, but not equally resistant to M. incognita and R. reniformis. Reproduction of R. reniformis on sunn hemp was nearly undetectable, whereas reproduction of M. incognita was greater than on resistant cotton (Auburn 623, Auburn 634) and up to 20% of that on susceptible cotton (Deltapine 16, Deltapine 50, or Deltapine 5409). Kenaf was confirmed to elevate populations of M. incognita to levels that devestate cotton, but found to support substantially less reproduction by R. reniformis than cotton does. Two populations of R. reniformis differed substantially in reproduction on kenaf even though the same populations reproduced similarly on cotton. In conclusion, distinguishing M. incognita from R. reniformis is essential to the management of nematodes in rotations involving kenaf, sunn hemp and cotton.     

Evaluation of resistance to root-knot nematode (Meloidogyne incognita) in okra cultivars

The root-knot nematode, Meloidogyne incognita, is one of the major limiting factors affecting plant growth and yield causing an estimated $100 billion loss per year worldwide. Synthetic pesticides, though instantaneously effective, are usually prohibitively expensive, not readily available, may cause hazards to both man and livestock, and inflict injury to the environment. Notable among the alternatives to nematicides is the use of resistant cultivars which are inexpensive and eco-friendly. In the present studies, twelve okra (Abelmoschus esculentus L) cultivars were evaluated for their resistance against M. incognita under field conditions. Ten-day old okra plants of test cultivars were inoculated with 3000 freshly hatched second stage juveniles of M. incognita. The nematode caused reductions in various growth parameters of all the cultivars to varying levels over their respective controls. None of the cultivars was found completely resistant. The cultivar ‘Sharmeeli’ was highly susceptible as >100 galls were recorded on the roots. Sharmeeli also showed maximum reductions in growth among the cultivars evaluated. The cultivars Anmol and Sindha were susceptible with 71–100 galls. The cultivars Sabz Pari, Super Star, PMS-55 and PMS Beauty were moderately susceptible with 31–70 galls and comparatively less reductions in growth. Cultivars Sanam, Dikshah, Arka Anamika, Ikra-1 and Ikra-2 with 11–30 galls were rated as moderately resistant and showed less damage by the nematode as compared to susceptible cultivars and their planting could provide a useful tool to control root-knot nematodes.     

Free-Living Plant-Parasitic Nematodes do not Affect the Efficiency of Seed Tuber Fungicide Treatment against <Emphasis Type="Italic">Rhizoctonia solani</Emphasis>

Stem canker on germinating potato sprouts is often caused by seed-borne inoculum of the fungus Rhizoctonia solani. However, high amounts of free-living plant-parasitic nematodes have been found in field patches of potato plants with stem canker. Fungicide treatment of the seed tubers can be used to avoid stem canker caused by seed-borne inoculum but it is unknown if nematodes can affect this. To investigate whether free-living plant-parasitic nematodes, the root-lesion nematode Pratylenchus penetrans or a combination of several plant-parasitic nematode genera in a full nematode community, may have a negative effect on the fungicide seed treatment, a pot experiment with seed tubers inoculated with R. solani, half of which were treated with fungicides, was performed. The seed-borne inoculum caused severe damage to the plants, while no fungal damages were observed on the fungicide treated plants. This shows that the nematodes did not affect the fungicide treatment. The probability of black scurf decreased in treatments with a full nematode community, which may be due to the action of fungal-feeding nematodes.     

Differential response of two pineapple cultivars (Ananas comosus (L.) Merr.) to SAR and ISR inducers against the nematode Rotylenchulus reniformis

We hypothesized that inducing systemic resistances can contribute to the control of the nematode Rotylenchulus reniformis in pineapple. In greenhouse experiments conducted in Martinique, the pineapple cultivars Smooth Cayenne and MD-2 were treated with methyljasmonate (JAME) and salicylic acid (SA), elicitors of induced systemic resistance (ISR) and systemic acquired resistance (SAR). The efficacy of the elicitors was tested by inoculating plantlets grown in individual pots with a monospecific population of R. reniformis reared on Vigna unguiculata. The final nematode populations, 45 days after inoculation on MD-2 treated with JAME were reduced by 67.0% (p = 0.006). Nematode populations on MD-2 plants treated with SA were reduced by 55.8% (p = 0.016). Nematode populations on SC were not reduced by the elicitors. In a second experiment, using split-root systems, JAME was applied to MD-2 plantlets and enzymatic activities involved in plant defense and stress responses were monitored for 14 h after treatment. Additional pots were inoculated with nematodes 24 h after JAME treatment and examined ten days later. Transient stress was observed along with an increase in enzymatic response after inoculation with nematodes. These results showed that the MD-2 was primed through an ISR by JAME. The question now arises whether ISR can be specifically induced only in certain pineapple cultivars. Results are discussed from the perspective of introducing new strategies to manage pineapple nematodes.     

Bitterness and Toxicity in Wild Yam (<Emphasis Type="Italic">Dioscorea</Emphasis> spp.) Tubers of Nepal

Wild yams make a significant contribution to diets of tribal people in Nepal. However, these wild tubers are unpalatable, taste bitter, produce inflammation and show occasional toxicity. Four wild yam species, which are eaten after primary treatment by Nepali aborigines, were analyzed for bitter and toxic principles. Bitter components were identified as furanoid norditerpenes (diosbulbins A and B). Diosbulbins A and B were found in the range of 0.023–0.046 and 0.151–0.442 g kg⁻¹, respectively. Results demonstrated that diosbulbin B, with an average value of 0.314 g kg⁻¹, was the principal bitter compound as compared to diosbulbin A (0.037 g kg⁻¹). The toxic alkaloid, dioscorine and histamine (an allergen) were not detected in these tubers, whereas cyanogens (as HCN equivalent) content were found ranging from 3.2 to 6.0 ppm. Our results revealed that Nepali wild yam tubers are not toxic varieties, as they do not contain either toxic dioscorine or histamine and cyanogens contents were satisfactorily below the safety limits. The inflammation and occasional toxicity observed could possibly be due to the presence of high level of oxalate in these tubers. Domestic cooking methods were found to be very efficient in removing bitterness, thus making the bitter yams palatable.     

Rapid detection of Meloidogyne spp. by LAMP assay in soil and roots

Loop-mediated isothermal amplification (LAMP), a novel DNA amplification technique, has been used to detect a variety of pathogens including viruses, fungi, bacteria and parasites. However, diagnosis of sedentary plant-parasitic nematode (PPN) species has not yet been attempted. In this study, we developed a universal LAMP set (RKN-LAMP) for the diagnosis of four common Meloidogyne species (Meloidogyne incognita, M. arenaria, M. javanica and M. hapla), and M. incognita-specific LAMP set (Mi-LAMP). In both assays, a typical ladder-like pattern on gel electrophoresis was observed in all positive samples but not in the negative controls. Amplification products were further confirmed using restriction analysis of the Hpa II enzyme, detection by visual inspection using SYBR Green I and the lateral flow dipstick (LFD) assay. The two LAMP sets were specifically able to detect four common Meloidogyne species and M. incognita populations having several different geographical origins and pathotypes. No cross reaction with DNA of other PPNs was observed. Sensitivity of the RKN- and Mi-LAMP was 10 and 100 fg of pure genome DNA respectively. Both LAMP sets could also amplified crude DNA isolated from the galled root tissue and from soil containing juveniles of M. incognita. The RKN- and Mi-LAMP sets offer the advantages of simplicity, rapidity and cost effectiveness. Both LAMP sets will be instrumental for the diagnosis of Meloidogyne spp. by local extension and regulatory personnel.     

Host suitability of peppers to the false root-knot nematode Nacobbus aberrans

The false root-knot nematode, Nacobbus aberrans, causes severe damage to field and greenhouse pepper crops in several localities of the American continent. No commercial peppers (Capsicum annuum) resistant to this nematode are available up to the present. Host suitability of 6 experimental and 3 commercial peppers (some of them carrying Me1 and Me7 resistance genes to Meloidogyne spp.) to two N. aberrans populations were evaluated under greenhouse experiments. None of the peppers was found to be resistant to the nematode. The evaluated parameters exhibited significant differences among some peppers tested within a single population and between populations for a single plant material. Some peppers carrying resistance showed higher nematode reproduction than some lines that did not possess resistance genes. These results confirmed that the genes conferring resistance to Meloidogyne spp. do not provide protection against this species of root-galling nematode. Host suitability of pepper lines carrying Me1 or Me7 resistance genes against N. aberrans is evaluated for the first time. Search for resistant genes against this nematode in wild peppers growing in areas where this nematode is indigenous should be promoted.     

Agronomic performance of no-tillage relay intercropping with maize under smallholder conditions in Central Brazil

In the context of conservation agriculture on small scale farms of the Brazilian Cerrado, we hypothesized that planting a cover crop in relay with a commercial crop improves the efficiency of use of available natural resources, increasing biomass for use as fodder without reducing the grain yield of the main crop. The objective of this study was to measure the performance of two intercropped systems in terms of total above-ground biomass production and maize (Zea mays) grain yield: pigeon pea (Cajanus cajan) and Brachiaria (Brachiaria ruziziensis) sown as cover crops in established maize under a no-tillage management. The cover crops were sown at two different dates and a comparison was made with the three crops sown as a sole crop at the early sowing date. The experiment was conducted during the 2007-2008 and 2008-2009 growing seasons. Maize grain yield was not reduced by the presence of the relay cover crops in comparison with maize as the sole crop, even when the cover crop was sown soon after maize emergence. In contrast, the production of above-ground biomass by the cover crop was significantly lower when grown with maize than it was when grown as a sole crop. In the intercropped systems, when sown early, the cover crop produced higher total biomass than when sown late. Total above-ground biomass production of maize intercropped with a cover crop was much higher than that of any of the crops sown alone: the total biomass (average of the two growing seasons) produced by maize and pigeon pea was more than double that of maize grown alone. The land equivalent ratio (LER) of maize grain yield and biomass production was higher than one whatever the intercropped system used. It was particularly high when maize was intercropped with early sown pigeon pea; grain yield LER and biomass LER reaching, respectively, 1.72 and 1.73 in 2007-2008 and 2.02 and 2.03 in 2008-2009. These high LER values provide evidence for the complementary and the high efficiency of use of available resources by the intercropped plants and thus the advantage of such systems to produce both maize grain and cover crop forage under the conditions of our study.     

Managing Meloidogyne incognita and Bemisia tabaci with thiacloprid in cucumber crops in China

Field trials were conducted to determine the potential use of thiacloprid for integrated Meloidogyne incognita and Bemisia tabaci B biotype control in cucumber (Cucumis sativus Linn.) in China. The following five treatments were evaluated: three thiacloprid doses (7.5, 15, and 30 kg ha⁻¹), an avermectin treatment (7.5 L ha⁻¹) and an untreated control. All thiacloprid application rates were effective for reducing the M. incognita and B. tabaci B biotype populations. M. incognita was reduced by 51.0%∼86.7% on 60th day and B. tabaci B biotype was reduced by about 37.2%∼95.3% within 21 days, respectively. In addition, greater thiacloprid doses resulted in fewer nematodes and whiteflies. Over two successive years, the cucumber plants that were treated with thiacloprid at a dose of 15 kg ha⁻¹ had the greatest plant height, plant vigor and marketable yield, which were 134.1 cm, 91, 1514.3 g plant⁻¹, respectively in 2010–2011 and 151.9 cm, 93, 1651.4 g plant⁻¹, respectively in 2011–2012. In addition, thiacloprid was superior to avermectin. The results of this study demonstrated that thiacloprid could be used in cucumber production for the integrated control of M. incognita and B. tabaci B biotype. Furthermore, a dose of 15 kg ha⁻¹ of thiacloprid was recommended for controlling nematode and whitefly populations according to the control effect and marketable cucumber yield.     

Host range study of Argentine Nacobbus aberrans sensu Sher populations and comments on the differential host test

The existence of races within the species Nacobbus aberrans sensu Sher has been confirmed; however, there is no consensus on a consistent system for race determination. Four plant species previously used as differential hosts in some N. aberrans race tests (tomato, pepper, sugarbeet and potato) were tested for susceptibility to seven nematode populations from Argentina. Plants were inoculated with second-stage juveniles and kept under glasshouse conditions at 21 °C for 90 days. The parameters evaluated (root gall index, egg mass index, and reproduction factor) in different nematode populations and plants showed significant differences. The reproductive fitness of the nematode populations differed among the plants that showed some degree of susceptibility. The results showed that N. aberrans comprises populations differing in host preference. Based on the nematode populations’ behaviour on these hosts, two groups were distinguished: i) populations that multiplied on all hosts, ii) populations that did not multiply on potato. The present work contributes to the analysis of criteria for developing a differential host test.     

Cis- and trans-protopinium,a novel nematicide,for the eco-friendly management of root-knot nematodes

Plant-derived nematicides are being increasingly used while select synthetic nematicides are phased out for environmental concerns. This is the first report on the in vitro nematicidal activity of cis- and trans-protopinium isolated from roots of Fumaria parviflora and its in vivo effect on the southern root-knot nematode Meloidogyne incognita. Cis- and trans-protopinium was isolated from the methanolic fraction FM2.1, and its structure elucidated using ¹³C and ¹H nuclear magnetic resonance (NMR). The NMR spectra were characterized using deuterated dimethyl sulfoxide (DMSO) at temperatures of 25 and 80 °C. In an in vitro study, over 120 h of incubation, the area under cumulative percent hatch inhibition and mortality of cis- and trans-protopinium reached 100% at a concentration of 200 μg mL⁻¹. In the greenhouse and field settings, cis- and trans-protopinium was evaluated against M. incognita on tomato at a concentration of 100, 200, and 300 μg mL⁻¹ for two consecutive seasons, that is, spring and autumn, in 2010. At a concentration of 300 μg mL⁻¹ in the greenhouse and field trials during spring and autumn, cis- and trans-protopinium significantly reduced the nematode galling index, the number of females per gram of root, and the reproduction factor, as well as increased plant height, fresh and dry shoot weights, and root length. Therefore, cis- and trans-protopinium can be used as an effective and safe nematicide against M. incognita on tomato in an organic and sustainable agricultural production system. Phytochemicals have various agricultural applications, especially to control economically important nematode pests.     

Screening of three sweet potato (Ipomoea batatas L.) cultivars for resistance to different virulence groups of root-knot nematodes (Meloidogyne spp.) under controlled conditions

The susceptibility of three sweet potato cultivars (Ipomoea batatas L.) C4, TIS 3290 and TIS 9162 was evaluated against 156 isolates of Meloidogyne spp. with the aim to include resistant/tolerant sweet potato cultivars in a crop rotation scheme for the management of root-knot nematodes. The nematode isolates corresponded to races 1, 2 and 3 of Meloidogyne arenaria (n = 7), races 1, 2, 3 and 4 of M. incognita (n = 131) and Meloidogyne javanica (n = 18). Also, the isolates of M. incognita were differentiated in virulence groups: Pepper (n = 35), Pepper-Mi (n = 25), Tomato (n = 41) and Tomato-Mi (n = 30), depending on their ability to parasitize resistant pepper and tomato cultivars. The tested isolates of M. javanica parasitized C4 and TIS 3290, but not TIS 9162, whereas M. arenaria parasitized C4 and TIS 9162, but not TIS 3290, and M. incognita was able to parasitize the three sweet potato cultivars tested. C4 was the most susceptible cultivar to all nematode species tested, especially M. incognita, TIS 3290 was the most resistant and TIS 9162 was in between (7.2, 62.9 and 26.9% of resistant plants, respectively). Susceptibility of the sweet potato cultivars showed slight variations depending on the race or virulence group of M. incognita. The results suggest that sweet potato cultivars TIS 3290 and TIS 9162 may be used as rotation crops in fields where root-knot nematodes are present, their selection depending on the Meloidogyne isolates present. The use of resistant sweet potato cultivars would be preferably combined with other management practices to avoid virulence selection in nematode isolates.     

Infestation assessment of root-knot nematodes (Meloidogyne spp.) associated with cucumber in the Pothowar region of Pakistan

Studies to estimate root-knot nematode infestations on cucumber were conducted during mid- to late-season at 378 randomly selected sites in 126 villages of the four districts across the Pothowar zone of the country. The overall mean infestation of root-knot nematodes in the region was found to be 15.66%. The studies revealed variations in the incidence and severity of root-knot nematodes in the four districts. The incidence of root-knot nematodes was the highest in Rawalpindi district (21.86%), followed by 13.89% in Attock. Of the four districts, the minimum incidence of 10.97% was recorded in Jhelum district. The maximum mean severity (3.79), measured in terms of the galling index, was found in Rawalpindi district, while the minimum (1.86) was observed in Jhelum district. The mean severities of root-knot nematodes in the districts of Attock and Chakwal were 2.66 and 2.19 respectively. Variations in incidence and severity were also observed among subdivisions of the districts. Of all the associated species of root-knot nematodes, Meloidogyne incognita constituted 78.53%, Meloidogyne javanica 19.03%, Meloidogyne arenaria 1.82% and Meloidogyne hapla 0.62%. M. incognita and M. javanica were recorded in all of the districts, with M. incognita predominating. M. incognita as a pure population was recorded in 29.63% of the villages, while the other three species were found as mixtures. The most common mixed population was M. incognita and M. javanica, observed in 70.37% of villages in the region. M. arenaria and M. hapla were not found together in any of the population mixtures. The results indicate that cucumber is severely attacked by root-knot nematodes, warranting adoption of strict control measures for its management.     

A cohort-based stochastic model of the population dynamic and long-term management of Conyza bonariensis in fruiting tree crops

Conyza bonariensis is currently a frequent and abundant weed in fruiting tree crops associated with non-tillage in Mediterranean climate areas, such as citrus groves and olive orchards. Because of the mild winters characteristic of this climate, an extended season of seedling emergence, from early autumn to early spring, is often found for this species, this leading to multiple annual cohorts. In this work, a cohort-based stochastic model of C. bonariensis population dynamics was developed and used to simulate the behaviour of the seed bank in Mediterranean fruiting tree crops under ten contrasting management strategies, including single or integrated herbicide and non chemical control measures. The demographic impact of tillage system (ploughing vs. no-till), the use of cover, and timing of herbicide applications was simulated. The model was parameterized with information taken from the literature. In the absence of any control and under no-tillage the modelled seed bank reached an average equilibrium density of 378,092 ± 10,865 seeds m⁻². The most effective management strategy integrated no-till, the use of cover and early and late applications of herbicides, which reduced the equilibrium densities of the seed bank by 78.7%. A sensitivity analysis indicated that C. bonariensis populations in Mediterranean fruiting tree crops are particularly sensitive to small changes in the demographic parameters associated with the earlier cohort and to the efficacy of early herbicide treatments. A diversified, integrated approach including different interventions of chemical and cultural nature appears to be the most successful strategy at the field level for controlling C. bonariensis in Mediterranean fruiting tree crops.     

Management of the root-knot nematode Meloidogyne incognita on tomato with combinations of different biocontrol organisms

The nematicidal effect of Pseudomonas fluorescens, Paecilomyces lilacinus, Pichia guilliermondii and Calothrix parietina singly or in combination was tested against root-knot nematode, Meloidogyne incognita. Treatments with P. fluorescens and P. lilacinus caused mortality of M. incognita as 45% and 30% of juveniles after 48 h of exposures, respectively compared to water control in vitro. Under greenhouse conditions, all treatments reduced the disease severity and enhanced plant growth compared to untreated control. Application of P. fluorescens, P. lilacinus and P. guilliermondii Moh 10 was more effective compared to C. parietina. There was a negative interaction between C. parietina and either P. lilacinus or P. guilliermondii. Fresh and dry weight of shoots and roots of plants were significantly reduced as a result of infection with M. incognita, however application of biocontrol agents singly or in mix recovered this reduction. Moreover, they enhanced the growth parameters compared with the control. Our results proved that application of different biocontrol agents (P. fluorescens, P. lilacinus and P. guilliermondii) not only has a lethal effect on nematode, but also enhances the plant growth, supplying many nutritional elements and induction the systemic resistance in plants. Presence of C. parietina as a soil inhabitant cyanobacterium could antagonize biocontrol agents leading to the reduction of their practical efficiency in soil.     

Inhibitory effects of cover crop mulch on germination and growth of Stellaria media (L.) Vill., Chenopodium album L. and Matricaria chamomilla L.

Cover crops may suppress weeds due to their competitive effects and the release of inhibitory compounds. We examined the inhibitory influence of 11 cover crop mulches on the germination and growth of weed species (Stellaria media (L.) Vill., Chenopodium album L. and Matricaria chamomilla L.) in laboratory, greenhouse and field experiments. In the laboratory, cover crop extracts were tested in germination bioassays at six concentrations (0–500 mg ml⁻¹). The germination rate and root length (i) were measured 10 days after treatment (DAT). Pot experiments were carried out in the greenhouse to investigate the effects of cover crop mulch (ii) incorporated into the soil on weed germination and weed dry mass. Field trials measured the suppressive effects of cover crops and cover crop mixtures on weeds (iii). Correlations were determined between the experiments to quantify the competition and the biochemical effects of cover crops separately. Cover crop extracts at a concentration of 125 mg ml⁻¹ (i) significantly reduced the weed germination rate by 47% and the root length by 32% on average. M. chamomilla showed a lower susceptibility to the extracts of S. alba, R. sativus var. niger and H. annuus compared to C. album and S. media. The mulch-soil mixtures (ii) significantly reduced the germination rate by 50% and the dry mass by 47% on average across all three weed species, while M. chamomilla showed the highest tolerance to the mulches of V. sativa and A. strigosa. The correlation analysis revealed a strong positive correlation between extract toxicity and field weed suppression and, thus, indicated a high impact of the biochemical effects of the tested cover crops on weed suppression, especially for S. media and M. chamomilla.