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B G H Timmermans - One of the best experts on this subject based on the ideXlab platform.
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the development validation and application of a Crop growth model to assess the potential of solanum sisymbriifolium as a Trap Crop for potato cyst nematodes in europe
Field Crops Research, 2009Co-Authors: B G H Timmermans, J Vos, T J StomphAbstract:Abstract Solanum sisymbriifolium (Lam.), a plant that was introduced as a Trap Crop for potato cyst nematodes, shows strong temperature limitation of its growth. Previous research indicated that the Crop needs to accumulate at least 700 g m −2 dry matter to achieve sufficient nematode control. In that context, three functionally different geographical zones can be distinguished: (i) a zone with insufficient growth, independent of sowing time, (ii) a zone with potentially sufficient growth if the Crop is allowed to grow for the whole growing season, and (iii) a zone with sufficient growth early or late in the growing season, opening the option to combine cultivation of the Trap Crop with another Crop in the same year. The aim of the current research was to delimit these zones for western and central Europe, by developing a model enabling simulation of the potential growth of S. sisymbriifolium in 64 locations between Scandinavia and Spain and between the UK and Hungary. A LINTUL type Crop growth model for potential growth was adapted to S. s isymbriifolium . Adaptations regarded particularly the relative growth rate of the leaf area, the specific leaf area, and the radiation use efficiency, that were made temperature dependent using experimental data. Furthermore, the leaf death rates were modelled as limited by light availability in the canopy. The model was calibrated with field data from an experiment in 2002, and validated on field experiments in 2001, 2003 and 2004, resulting in a root mean square error (RMSE) of 118.1 g m −2 Crop dry matter and a mean deviation (MD) of −15.9 g m −2 for the validation data. Simulations were done for the 64 sites, using weather data from 1996 to 1999, and the studied area was divided in the three zones (i, ii and iii) as described above. In all regions the Crop could reach the required minimum size, although barely so in Scandinavia and the north of the United Kingdom. Zone (ii) included the south of the United Kingdom and Sweden, The Netherlands, Germany, Belgium and the north of France. Zone (iii) included the rest of France, Spain, Portugal, Italy, and Hungary; here temperature and radiation suffice for the Crop to reach its required minimum size in only part of the growing season, leaving space for an other (main) Crop in the same season, at least in the absence of water limitations.
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field performance of solanum sisymbriifolium a Trap Crop for potato cyst nematodes i dry matter accumulation in relation to sowing time location season and plant density
Annals of Applied Biology, 2007Co-Authors: B G H Timmermans, J Vos, T J Stomph, J G W Van Nieuwburg, P E L Van Der Putten, P G MolendijkAbstract:Solanum sisymbriifolium is an interesting Trap Crop to control potato cyst nematodes. A series of field experiments was carried out in the Netherlands between 2001 and 2003 to test its performance under field conditions. Experimental factors included sowing time, sowing density and site. Rate of germination, plant establishment and change over time in light interception were monitored. Growth analysis was performed at 7 and 14?weeks after emergence, and dry weight of component plant parts was determined. Time to 50% emergence was 36-38?days for planting at early April and declined to minimum values of ca 8-11?days when planting took place in June, July or the first week of August. When planted later, time to 50% germination increased again. Time to 50% light interception showed a similar trend with sowing time; minimum time was 35-40?days for planting between June and half of July. Planting before May did not advance Crop growth. Crop performance was very variable across years and sites when planted later than the end of July to beginning of August. Dry matter accumulation up to 400?g?m?2 was found at 7?weeks after emergence and up to 1040?g?m?2 after 14?weeks. At 7?weeks after emergence, dry matter production increased with planting density (range 50-400?m?2), but no statistically significant differences were found after 14?weeks. A seed rate of 100?m?2 seems generally sufficient. Radiation use efficiency was 1.69?g?MJ?1 PAR (SE?=?0.0208). Dry matter accumulation (2002-2003) was somewhat higher in Wageningen (51°58'N) on light sandy soil than in Flevoland (52°31?N) on clay soil and in Drenthe (52°51?N) on reclaimed peat soil. It is concluded that above-ground growth of S.?sisymbriifolium in the Netherlands is adequate if planted between early May and the end of July
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solanum sisymbriifolium lam a Trap Crop for potato cyst nematodes
Solanum sisymbriifolium Lam, 2005Co-Authors: B G H TimmermansAbstract:Keywords: Solanum sisymbriifolium , Globodera pallida , Globodera rostochiensis , germination, light use efficiency, Crop growth, Crop management, root length density, hatching, Trap Crop, tolerance, Phytophthora infestans , resistance. Potato cyst nematodes (PCN), Globodera pallida (Stone) and G. rostochiensis ( Woll .) continue to be a major pest in potato growing areas, in spite of existing control measures. Therefore, Solanum sisymbriifolium (Lam.) was introduced as a Trap Crop for PCN in Western Europe . The current study was performed to collect quantitative information on the ecology, agronomy and potential nematode reduction of S. sisymbriifolium Crops in The Netherlands. The emergence rate of S. sisymbriifolium was almost zero at temperatures below 8 °C. The relation between germination and temperature at sub-optimal temperatures is adequately described with expolinear and quadratic equations. These are relatively simple, and applicable in modelling germination of other plant species grown in conditions near their base temperature. Plantings between May and the end of July led to a Crop with full ground cover. Initial growth was slow, but indeterminate and accumulated amounts of above-ground biomass were high (more than 10 tons ha - 1 dry matter after 100 days). Root length density could be reasonably well assessed from above-ground Crop characteristics, and was linked to theoretically possible nematode reductions. In a greenhouse study in containers, nematode population reduction was found to be related to root length density and length of the growth period of the Crop. After 150 days of Crop growth the PCN population density was reduced with 75% on average; in the soil layer with maximum root length density of 5.8 cm cm - 3 the PCN population reduction was 86%. A general formula was derived to calculate the time gained to reduce the PCN population density below threshold levels, comparing a scenario with cultivation of one Crop of S. sisymbriifolium , followed by non-hosts or fallow, with a scenario with natural decay of the PCN population (non-hosts or fallow throughout). Calculations indicated that 75% reduction of PCN amounts to 4 years time gain to sanitation. S. sisymbriifolium is highly tolerant to PCN, enabling successful growth in PCN infested soil. Furthermore, it is highly resistant against several isolates of Phytophthora infestans ( Mont. ) de Bary , with low infection efficiency and lesion growth rates. Therefore, S. sisymbriifolium is an interesting PCN Trap Crop, deserving further development.
Louisemarie Dandurand - One of the best experts on this subject based on the ideXlab platform.
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effect of the Trap Crop solanum sisymbriifolium on globodera pallida globodera tabacum and globodera ellingtonae
Journal of Nematology, 2019Co-Authors: Louisemarie Dandurand, Inga A Zasada, J A LamondiaAbstract:The effect of the nematode Trap Crop Solanum sisymbriifolium was assessed against three Globodera spp., the potato cyst nematode Globodera pallida (in Idaho), the recently described Globodera ellingtonae (in Oregon), and the tobacco cyst nematode Globodera tabacum (in Connecticut) in field trials. At all locations the ability of S. sisymbriifolium to reduce Globodera encysted second-stage juveniles (J2) in egg densities compared to fallow was considered. For G. ellingtonae, the impact of planting and termination dates of S. sisymbriifolium on final egg densities was also evaluated; and for G. pallida, the ability of the nematode to reproduce on potato (Solanum tuberosum) after exposure to S. sisymbriifolium was determined. Encysted J2 in egg densities of all three Globodera spp. declined from 25 to 68% after Trap Cropping with S. sisymbriifolium. For G. pallida, S. sisymbriifolium reduced final encysted J2 in egg density by 23 to 50% compared to the fallow treatment, and significantly decreased G. pallida reproduction on potato after exposure to S. sisymbriifolium by 99 to 100% compared to the fallow treatment (P < 0.0001). For G. ellingtonae, the planting date of S. sisymbriifolium in May or June did not impact final egg densities (P = 0.32). Rather, percentage reduction in G. ellingtonae encysted J2 in egg density was most influenced by the length of time to which nematodes were exposed to S. sisymbriifolium, with 30 and 81% reduction after 6 vs 12 wk of exposure, respectively (P < 0.0001). Similar levels of nematode reduction after S. sisymbriifolium were observed for G. tabacum after 12 to 14 wk of exposure to the Trap Crop; G. tabacum density changes consisted of a 114% increase after susceptible tobacco, a 65% decrease after resistant tobacco, and an 88% decrease after S. sisymbriifolium compared to bare soil. In conclusion, this research demonstrates the widespread applicability of S. sisymbriifolium in reducing a diversity of Globodera spp. present in the USA. The effect of the nematode Trap Crop Solanum sisymbriifolium was assessed against three Globodera spp., the potato cyst nematode Globodera pallida (in Idaho), the recently described Globodera ellingtonae (in Oregon), and the tobacco cyst nematode Globodera tabacum (in Connecticut) in field trials. At all locations the ability of S. sisymbriifolium to reduce Globodera encysted second-stage juveniles (J2) in egg densities compared to fallow was considered. For G. ellingtonae, the impact of planting and termination dates of S. sisymbriifolium on final egg densities was also evaluated; and for G. pallida, the ability of the nematode to reproduce on potato (Solanum tuberosum) after exposure to S. sisymbriifolium was determined. Encysted J2 in egg densities of all three Globodera spp. declined from 25 to 68% after Trap Cropping with S. sisymbriifolium. For G. pallida, S. sisymbriifolium reduced final encysted J2 in egg density by 23 to 50% compared to the fallow treatment, and significantly decreased G. pallida reproduction on potato after exposure to S. sisymbriifolium by 99 to 100% compared to the fallow treatment (P < 0.0001). For G. ellingtonae, the planting date of S. sisymbriifolium in May or June did not impact final egg densities (P = 0.32). Rather, percentage reduction in G. ellingtonae encysted J2 in egg density was most influenced by the length of time to which nematodes were exposed to S. sisymbriifolium, with 30 and 81% reduction after 6 vs 12 wk of exposure, respectively (P < 0.0001). Similar levels of nematode reduction after S. sisymbriifolium were observed for G. tabacum after 12 to 14 wk of exposure to the Trap Crop; G. tabacum density changes consisted of a 114% increase after susceptible tobacco, a 65% decrease after resistant tobacco, and an 88% decrease after S. sisymbriifolium compared to bare soil. In conclusion, this research demonstrates the widespread applicability of S. sisymbriifolium in reducing a diversity of Globodera spp. present in the USA.
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effect of the Trap Crop solanum sisymbriifolium and two biocontrol fungi on reproduction of the potato cyst nematode globodera pallida
Annals of Applied Biology, 2016Co-Authors: Louisemarie Dandurand, G R KnudsenAbstract:The potato cyst nematode, Globodera pallida, is one of the most important pests of potato worldwide. Owing to regulatory considerations and potential environmental impact, control options for this nematode are becoming increasingly limited. Solanum sisymbriifolium and biological control agents offer viable alternative options for controlling G. pallida. Therefore, experiments were conducted to determine the effect of the nematode Trap Crop S. sisymbriifolium, alone or in combination with the biocontrol agents Trichoderma harzianum or Plectosphaerella cucumerina, on population decline of G. pallida. Experiments were conducted for three different ‘Cropping systems’: potato (Solanum tuberosum), S. sisymbriifolium, or soil only (fallow), each followed by a potato Crop. Soil was amended with P. cucumerina, T. harzianum or left unamended, and then infested with nematodes at a rate of five eggs g−1 of soil. After 16 weeks in the greenhouse, plants were removed and the soil containing cysts was refrigerated at 4°C for 8 weeks, and then planted to potato. Cysts of G. pallida were counted after an additional 16-week period. The Pf/Pi of G. pallida was significantly reduced by 99% in potato following S. sisymbriifolium compared to both the potato-following-fallow and the potato-following-potato treatments. Amendment of soil with T. harzianum significantly reduced Pf/Pi of G. pallida by 42–47% in the potato-following-potato but not in either the potato-after-fallow nor in the potato-after-S. sisymbriifolium cycles which supports evidence that the plant species may play a role in the biocontrol activity of this fungus. Addition of the fungus P. cucumerina resulted in a 64% decrease in Pf/Pi in the potato-following-fallow in one experiment, and an 88% decrease in Pf/Pi in potato-following-potato but the decrease in Pf/Pi was not consistent over all experiments. However, both biocontrol fungi resulted in lower numbers of progeny cysts after an initial 16-week incubation with potato. To look at the effect of varied population density of the nematode on efficacy of S. sisymbriifolium to reduce G. pallida populations, potato, S. sisymbriifolium, or barley were planted into soil infested with G. pallida at rates of 5, 20 or 40 eggs g−1 soil applied as cysts (20, 80 or 160 cysts pot−1). After 16 weeks, numbers of cysts produced in each treatment were determined for each infestation rate. No new cysts were recovered from either S. sisymbriifolium or barley treatments, confirming that neither plant is a host for G. pallida. High numbers of cysts were recovered with potato. Soil from each treatment (containing original cysts and newly-formed cysts when present) were then planted with potato. After an additional 16 weeks, few cysts were found in the potato-after- S. sisymbriifolium treatments regardless of initial infestation rate. When potato followed barley, numbers of cysts were similar to those found after a single cycle of potato, indicating that the barley Crop had no effect on the survival of initial inoculum. Overall, these results suggest that S. sisymbriifolium has potential to significantly reduce G. pallida populations, and also that the Cropping system (i.e. the sequence of non-host and host plants) may play a significant role in the efficacy of fungal biological control agents.
T J Stomph - One of the best experts on this subject based on the ideXlab platform.
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the development validation and application of a Crop growth model to assess the potential of solanum sisymbriifolium as a Trap Crop for potato cyst nematodes in europe
Field Crops Research, 2009Co-Authors: B G H Timmermans, J Vos, T J StomphAbstract:Abstract Solanum sisymbriifolium (Lam.), a plant that was introduced as a Trap Crop for potato cyst nematodes, shows strong temperature limitation of its growth. Previous research indicated that the Crop needs to accumulate at least 700 g m −2 dry matter to achieve sufficient nematode control. In that context, three functionally different geographical zones can be distinguished: (i) a zone with insufficient growth, independent of sowing time, (ii) a zone with potentially sufficient growth if the Crop is allowed to grow for the whole growing season, and (iii) a zone with sufficient growth early or late in the growing season, opening the option to combine cultivation of the Trap Crop with another Crop in the same year. The aim of the current research was to delimit these zones for western and central Europe, by developing a model enabling simulation of the potential growth of S. sisymbriifolium in 64 locations between Scandinavia and Spain and between the UK and Hungary. A LINTUL type Crop growth model for potential growth was adapted to S. s isymbriifolium . Adaptations regarded particularly the relative growth rate of the leaf area, the specific leaf area, and the radiation use efficiency, that were made temperature dependent using experimental data. Furthermore, the leaf death rates were modelled as limited by light availability in the canopy. The model was calibrated with field data from an experiment in 2002, and validated on field experiments in 2001, 2003 and 2004, resulting in a root mean square error (RMSE) of 118.1 g m −2 Crop dry matter and a mean deviation (MD) of −15.9 g m −2 for the validation data. Simulations were done for the 64 sites, using weather data from 1996 to 1999, and the studied area was divided in the three zones (i, ii and iii) as described above. In all regions the Crop could reach the required minimum size, although barely so in Scandinavia and the north of the United Kingdom. Zone (ii) included the south of the United Kingdom and Sweden, The Netherlands, Germany, Belgium and the north of France. Zone (iii) included the rest of France, Spain, Portugal, Italy, and Hungary; here temperature and radiation suffice for the Crop to reach its required minimum size in only part of the growing season, leaving space for an other (main) Crop in the same season, at least in the absence of water limitations.
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field performance of solanum sisymbriifolium a Trap Crop for potato cyst nematodes i dry matter accumulation in relation to sowing time location season and plant density
Annals of Applied Biology, 2007Co-Authors: B G H Timmermans, J Vos, T J Stomph, J G W Van Nieuwburg, P E L Van Der Putten, P G MolendijkAbstract:Solanum sisymbriifolium is an interesting Trap Crop to control potato cyst nematodes. A series of field experiments was carried out in the Netherlands between 2001 and 2003 to test its performance under field conditions. Experimental factors included sowing time, sowing density and site. Rate of germination, plant establishment and change over time in light interception were monitored. Growth analysis was performed at 7 and 14?weeks after emergence, and dry weight of component plant parts was determined. Time to 50% emergence was 36-38?days for planting at early April and declined to minimum values of ca 8-11?days when planting took place in June, July or the first week of August. When planted later, time to 50% germination increased again. Time to 50% light interception showed a similar trend with sowing time; minimum time was 35-40?days for planting between June and half of July. Planting before May did not advance Crop growth. Crop performance was very variable across years and sites when planted later than the end of July to beginning of August. Dry matter accumulation up to 400?g?m?2 was found at 7?weeks after emergence and up to 1040?g?m?2 after 14?weeks. At 7?weeks after emergence, dry matter production increased with planting density (range 50-400?m?2), but no statistically significant differences were found after 14?weeks. A seed rate of 100?m?2 seems generally sufficient. Radiation use efficiency was 1.69?g?MJ?1 PAR (SE?=?0.0208). Dry matter accumulation (2002-2003) was somewhat higher in Wageningen (51°58'N) on light sandy soil than in Flevoland (52°31?N) on clay soil and in Drenthe (52°51?N) on reclaimed peat soil. It is concluded that above-ground growth of S.?sisymbriifolium in the Netherlands is adequate if planted between early May and the end of July
John P. Sanderson - One of the best experts on this subject based on the ideXlab platform.
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Designing an effective Trap Cropping strategy: the effects of attraction, retention and plant spatial distribution
Journal of Applied Ecology, 2012Co-Authors: Matthew H. Holden, Jan P. Nyrop, Doo-hyung Lee, Stephen P. Ellner, John P. SandersonAbstract:1.Trap Cropping, the use of alternative host plants to reduce pest damage to a focal cash Crop or other managed plant population, can be a sustainable strategy for pest control, but in practice it has often failed to reach management goals. Of the few successful Trap Cropping examples at a commercial scale, nearly all have included supplemental management strategies that reduce pest dispersal off the Trap Crop. In contrast, the Trap Cropping literature has focused extensively on Trap plant attractiveness. 2.To test whether the dispersal of insects off Trap plants is as important as the anecdotal evidence suggests, we developed a simple model to understand how a Trap plant's spatial configuration within a field, its attractiveness and its ability to retain pests affect pest density on a target cash Crop. 3.The model predicts that when Trap Crop retention is low, Trap Cropping is ineffective, and small increases in retention offer little improvement. However, when retention is high, small differences in retention dramatically affect Trap Cropping efficacy. In contrast, when the attractiveness of a Trap Crop is high, further increases in attractiveness have little effect on Trap Cropping efficacy. 4.Placing Trap plants close together is most often detrimental to pest management because it leaves large portions of the field without nearby Traps. However, planting the Trap Crop in rows often does not clump the landscape enough to cause this detrimental effect. 5.Synthesis and applications. The predictions from our model confirm the anecdotal evidence that Trap Cropping failures may be attributed to a focus on attraction at the expense of retention. A very high retention rate is required for effective reduction of pest densities. Therefore, additional practices that prevent insects from dispersing back into the cash Crop may be essential for effective Trap Cropping designs. These techniques include Trap vacuuming, Trap harvesting, sticky Traps, planting a high proportion of Trap plants or applications of pesticides or natural enemies to the Trap Crop. © 2012 The Authors. Journal of Applied Ecology
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Effect of host experience of the greenhouse whitefly, Trialeurodes vaporariorum, on Trap Cropping effectiveness.
Entomologia Experimentalis Et Applicata, 2010Co-Authors: Doo-hyung Lee, Jan P. Nyrop, John P. SandersonAbstract:This study evaluated whether experience of Trialeurodes vaporariorum (Westwood) (Hemiptera: Aleyrodidae) on a poinsettia cash Crop, Euphorbia pulcherrima Willd. ex Koltz (Euphorbiaceae), influences the effectiveness of an eggplant Trap Crop, Solanum melongena L. (Solanaceae). Two whitefly strains were tested: one was reared on poinsettia (poinsettia-strain) and a second was reared on bean [Phaseolus vulgaris L. (Fabaceae)] (bean-strain). We first determined whether host experience altered the preference of adult whiteflies for eggplant and their survivorship on poinsettia. Then, we determined whether changes in the preference and/or survivorship influenced the effectiveness of the Trap Cropping. Adult whiteflies from both strains consistently redistributed and settled on an eggplant Trap Crop in significantly higher numbers compared to poinsettia. The adult survivorship of the poinsettia-strain whiteflies was slightly higher on poinsettia than on the bean-strain. In research greenhouse experiments, we found that the Trap Cropping consistently resulted in a decrease in the density of the poinsettia-strain whiteflies on the cash Crop compared to that in monoculture. However, higher adult whitefly survivorship on eggplant than on poinsettia could compromise its effectiveness as a Trap Crop in poinsettia. The effectiveness of Trap Cropping, as reflected by the whitefly density reduction on a poinsettia cash Crop, was significantly smaller than the attractiveness of the Trap Crop, as indicated by the whitefly abundance on an eggplant Trap Crop.
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Attraction of Trialeurodes vaporariorum and Bemisia argentifolii to eggplant, and its potential as a Trap Crop for whitefly management on greenhouse poinsettia
Entomologia Experimentalis Et Applicata, 2009Co-Authors: Doo-hyung Lee, Jan P. Nyrop, John P. SandersonAbstract:Trap Cropping, though promising, has had little evaluation in greenhouses. This study evaluated eggplant, Solanum melongena L. (Solanaceae), as a Trap Crop for two whitefly species, Trialeurodes vaporariorum (Westwood) and Bemisia argentifolii Bellows & Perring (both Hemiptera: Aleyrodidae), on greenhouse poinsettia, Euphorbia pulcherrima Willd. ex Koltz (Euphorbiaceae). Because the two whitefly species co-occur in greenhouses, a common Trap Crop for both whiteflies is desirable. When adults were provided a choice between eggplant and poinsettia in a cage, 60% of B. argentifolii and 98% of T. vaporariorum were observed on eggplant after 3 days. However, when adults were given eggplant after first settling on poinsettia, only 38% of B. argentifolii were later found on eggplant, whereas 95% of T. vaporariorum moved to eggplant. In a greenhouse experiment, eggplant did not affect either the spatial distribution or density of adult B. argentifolii on poinsettias. In contrast, eggplant changed the spatial distribution of T. vaporariorum within 3 days by attracting and retaining the adults. However, the attractiveness of eggplant did not result in a reduced number of T. vaporariorum on poinsettias compared with poinsettias in monoculture. Adult T. vaporariorum mortality was high on poinsettias and this likely caused adult density on poinsettias in monoculture to decrease as fast as that under Trap Cropping. A simulation model was developed to examine how adult whitefly mortality on poinsettia influences Trap Cropping effectiveness. When whitefly mortality was high, simulated densities were similar to the experimental data. This reveals an unexpected factor, pest mortality on the main Crop, that can influence the relative effectiveness of Trap Cropping. Our results indicate that eggplant will not work unilaterally as a Trap Crop for B. argentifolii. For T. vaporariorum, attraction to eggplant might be useful as a Trap Crop system when whitefly mortality on the main Crop is not high.
G R Knudsen - One of the best experts on this subject based on the ideXlab platform.
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effect of the Trap Crop solanum sisymbriifolium and two biocontrol fungi on reproduction of the potato cyst nematode globodera pallida
Annals of Applied Biology, 2016Co-Authors: Louisemarie Dandurand, G R KnudsenAbstract:The potato cyst nematode, Globodera pallida, is one of the most important pests of potato worldwide. Owing to regulatory considerations and potential environmental impact, control options for this nematode are becoming increasingly limited. Solanum sisymbriifolium and biological control agents offer viable alternative options for controlling G. pallida. Therefore, experiments were conducted to determine the effect of the nematode Trap Crop S. sisymbriifolium, alone or in combination with the biocontrol agents Trichoderma harzianum or Plectosphaerella cucumerina, on population decline of G. pallida. Experiments were conducted for three different ‘Cropping systems’: potato (Solanum tuberosum), S. sisymbriifolium, or soil only (fallow), each followed by a potato Crop. Soil was amended with P. cucumerina, T. harzianum or left unamended, and then infested with nematodes at a rate of five eggs g−1 of soil. After 16 weeks in the greenhouse, plants were removed and the soil containing cysts was refrigerated at 4°C for 8 weeks, and then planted to potato. Cysts of G. pallida were counted after an additional 16-week period. The Pf/Pi of G. pallida was significantly reduced by 99% in potato following S. sisymbriifolium compared to both the potato-following-fallow and the potato-following-potato treatments. Amendment of soil with T. harzianum significantly reduced Pf/Pi of G. pallida by 42–47% in the potato-following-potato but not in either the potato-after-fallow nor in the potato-after-S. sisymbriifolium cycles which supports evidence that the plant species may play a role in the biocontrol activity of this fungus. Addition of the fungus P. cucumerina resulted in a 64% decrease in Pf/Pi in the potato-following-fallow in one experiment, and an 88% decrease in Pf/Pi in potato-following-potato but the decrease in Pf/Pi was not consistent over all experiments. However, both biocontrol fungi resulted in lower numbers of progeny cysts after an initial 16-week incubation with potato. To look at the effect of varied population density of the nematode on efficacy of S. sisymbriifolium to reduce G. pallida populations, potato, S. sisymbriifolium, or barley were planted into soil infested with G. pallida at rates of 5, 20 or 40 eggs g−1 soil applied as cysts (20, 80 or 160 cysts pot−1). After 16 weeks, numbers of cysts produced in each treatment were determined for each infestation rate. No new cysts were recovered from either S. sisymbriifolium or barley treatments, confirming that neither plant is a host for G. pallida. High numbers of cysts were recovered with potato. Soil from each treatment (containing original cysts and newly-formed cysts when present) were then planted with potato. After an additional 16 weeks, few cysts were found in the potato-after- S. sisymbriifolium treatments regardless of initial infestation rate. When potato followed barley, numbers of cysts were similar to those found after a single cycle of potato, indicating that the barley Crop had no effect on the survival of initial inoculum. Overall, these results suggest that S. sisymbriifolium has potential to significantly reduce G. pallida populations, and also that the Cropping system (i.e. the sequence of non-host and host plants) may play a significant role in the efficacy of fungal biological control agents.
