The Use of Soil Solarization for the Management of Soilborne Plant Pathogens in Strawberry and Red Raspberry Production

Abstract

Root rot caused by Phytophthora fragariae var. fragariae and P. fragariae var. rubi are major concerns in strawberry and raspberry production in the Pacific Northwest. Of lesser importance is black root rot of strawberry, caused by a complex of fungi and nematodes. Soil solarization was evaluated in 1997 in a strawberry planting and in 1998 in a raspberry planting for: (i) enhancing plant health and growth, and (ii) reducing population densities of root-destroying pathogens. Plots were solarized from mid-July to mid-September. Maximum and mean soil temperatures in solarized plots recorded at 10 cm depth were 48 and 33°C in the strawberry plots and 46 and 29°C in the raspberry plots. These temperatures were 7 to 17°C higher than temperatures recorded in nonsolarized plots. Soil collected after solarization was assayed by growing bait plants, cv. Totem strawberry or cv. Qualicum raspberry, at 15°C for 6 weeks in saturated soil to promote infections. Root health and plant growth were evaluated after 6 weeks. Solarization significantly reduced (P < 0.05) root necrosis and increased root weight of bait plants compared to plants grown in soil from nonsolarized plots. Infection of strawberry roots by P. fragariae, Pythium, Rhizoctonia, and Cylindrocarpon spp. was reduced (P < 0.05) by solarization in sampled soil. Disease was reduced in cv. Hood strawberries and Qualicum and Skeena red raspberries planted in solarized field plots. In the second growing season, total number and number of healthy primocanes of Qualicum plants were greater (P < 0.05) in solarized plots compared to nonsolarized plots. Solarization combined with applications of mefenoxam was no more effective in controlling diseases than solarization alone, but better than mefenoxam alone. Skeena plants responded similarly, but the differences were not significant. Red raspberry plants growing in solarized soil yielded more fruit than plants growing in nonsolarized soil in the third year after solarization. Solarization has potential as a component in an integrated pest management program of root diseases in raspberry and strawberry production, particularly within the first 2 years following planting.

New strains obtained after UV treatment and protoplast fusion of native Trichoderma harzianum: their biocontrol activity on Pyrenochaeta lycopersici

“…Although the use of MeBr-chloropicrin eradicates many of the fungi involved in root rot complex, it has been shown that reinvasion by fast growing fungi may lessen the effectiveness of fumigation in the later growing season (Pinkerton et al 2002). The control of P. lycopersici in Chile is accomplished through fumigation with this chemical, which contaminates the environment, affects the ozone layer, destroys the soil microflora, and must be applied every season because of its null residual activity and the rapid re-colonization of soils by the phytopathogens (Ristaino and Thomas, 1997;Pinkerton et al 2002). Several disease management practices have been proposed to replace MeBr (Ristaino and Thomas, 1997;Fiume and Fiume, 2003).…”

Biocontrol of root and crown rot in tomatoes under greenhouse conditions using Trichoderma harzianum and Paenibacillus lentimorbus. Additional effect of solarization

“…In Chile, the control of the complex already mentioned is accomplished through fumigation with MeBr. This chemical contaminates the environment, affects the ozone layer, destroys the soil microflora, and must be applied every season because of its null residual activity and the rapid re-colonisation of soils by the phytopathogens (Ristaino and Thomas, 1997;Pinkerton et al 2002). Considering the difficulty to generate suppressive soils similar to the natural ones, the use of selected biocontrol microorganisms could provide an alternative to the use of chemical fungicides.…”

Forest nurseries face critical choices with the loss of methyl bromide fumigation

“…Solarization can be somewhat effective in those areas, but is limited by the number of sunny days (Hildebrand 1989). For example, Pinkerton et al (2002) found that populations of Pythium, Phytophthora, Rhizoctonia and Cylindrocarpon, but not Fusarium, were reduced in solarization studies involving strawberries and red raspberries in Oregon and Washington.…”

“…To our knowledge, little to no research has been conducted regarding genetic host resistance against soilborne pests; most resistance-screening programs have targeted host-specific pathogens such as the foliar and stem rusts of pine. Heat treatment and biological control methods have been tested and are considered too expensive, impractical, or of limited efficacy at this stage of development (Hildebrand 1989;James et al 2004;Pinkerton et al 2002). However, new pesticide chemistries are continuously being tested for their efficacy against specific pests (Zasada et al 2012), and progress is being made in pathogen identification and detection (Weiland 2011;Weiland et al 2013).…”