Comparison of Crop Rotation for Verticillium Wilt Management and Effect on Pythium Species in Conventional and Organic Strawberry Production

Abstract

The effects of broccoli and lettuce rotations on population densities of Verticillium dahliae and Pythium spp. in soil and on strawberry (Fragaria × ananassa) growth, yield, and Verticillium wilt were evaluated in conventional and organic production systems in California for 2 years. Under both management systems, strawberry was planted after two successive crops of broccoli or lettuce. The control treatment in the conventional field was strawberry planted in soils fumigated with methyl bromide + chloropicrin. Preplant densities of V. dahliae and Pythium sp. did not differ in these fields. At the end of the second broccoli crop, V. dahliae densities in conventional plots had declined by 44% in both years. In contrast, after the second broccoli crop, densities in organic fields decreased 47% in 2000 and 25% in 2001. In general, there were no differences in V. dahliae inoculum densities in organic and conventional plots following lettuce rotations. After the second vegetable production cycle, population densities of V. dahliae in broccoli rotated organic (24 CFU/g of soil in 2000 and 27 CFU/g of soil in 2001) or conventional (23 CFU/g of soil in 2000 and 19 CFU/g of soil in 2001) fields were significantly lower than those in lettuce rotated organic (40 CFU/g of soil in 2000 and 42 CFU/g of soil in 2001) or conventional (39 CFU/g of soil in 2000 and 35 CFU/g of soil in 2001) fields. However, crop rotation treatments had no consistent effect on the inoculum densities of Pythium spp. Canopy diameters of strawberry plants grown in rotation with broccoli were not different from those in fumigated control plots, whereas those from lettuce plots were 10% smaller. Strawberry plant nutrient analysis showed that fertilizer inputs into organic or conventional production were not responsible for the observed differences in plant size. Increases in strawberry yields were not consistent between years. Verticillium wilt incidence on strawberry was 12 to 24% lower in fields rotated with broccoli compared with fields rotated with lettuce. Wilt severity on strawberry was 22 to 36% lower in fields rotated with broccoli compared with those rotated with lettuce. The strategy of using broccoli rotation coupled with postharvest incorporation of broccoli residue continues to show promise as a tool in the management of Verticillium wilt in both conventional and organic strawberry production systems.

Effects of organic vs. conventional farming system on yield and quality of strawberry grown as an annual or biennial crop in southern Italy

“…The conventional farming system produced strawberry plants with higher leaf area and dry weight compared with the organic plants (Table 5). These results are consistent with previous reports (Baruzzi et al, 2009;Njoroge and Kabir, 2009) of a higher yield and canopy growth in the case of conventional management compared to organic farming. The different performances of the two farming methods did not appear to be caused by soil borne diseases, since no plant symptoms were detected, but they may be related to the faster action of the conventional mineral fertilizer compared to the organic manure.…”

Advances and Trends in Organic Fruit and Vegetable Farming Research

“…Consequently, cultural practices that promote the expression of antimicrobial qualities within the resident microbiome, such as the application of organic matter or organic compound amendments (Akhtar and Malik 2000; Oka et al 2007;Alsanius et al 2009;Giotis et al 2009;Oka 2010;Lopes et al 2011;Somasekhara et al 2013) or the use of cover crops and rotation (Viaene and Abawi 1998;Njoroge et al 2009) help minimize disease pressure on the crop. Depending on the type of organic amendment and compost, multiple studies have reported a major or moderate suppressive effect of compost or compost tea on diseases such as bacterial spot (Xanthomonas vesicatoria), early blight (Alternaria solani), bacterial canker (Clavibacter michiganensis), corky root rot (Pyrenochaeta lycopersici), gray mould (B. cinerea), F.…”

“…Disease suppression by compost was also influenced by optimum soil conditions and nutrient supply. Crop rotation with broccoli (Brassica oleracea) to reduce the microsclerotia population in the soil and the postharvest incorporation of broccoli residues constitute a tool to limit Verticillium wilt in strawberry and cauliflower (Xiao et al 1998;Subbarao et al 2007;Njoroge et al 2009). …”

Cultural Practices Influencing Biological Management of Crop Diseases

“…Likewise, wilt severity was also reduced to a greater extent in fi elds rotated with broccoli, compared with the fi elds rotated with lettuce. The usefulness of employing broccoli rotation coupled with postharvest incorporation of broccoli residue was indicated by this investigation (Njoroge et al 2009 ) .…”