| Replant diseases of strawberry caused by different pathogens under monocultureconditions can reduce both the yield and the quality of strawberry on a large scale, which iscurrently the most serious obstacle for strawberry production. In order to control thereplant diseases of strawberry, a bio-product, Kangdi 3, developed and produced byQinghuangdao Leading Science And Technology Development Co., Ltd and theLaboratory of Plant Disease Epidemiology And Integrated Control, Agricultural Universityof Hebei, was tested in two greenhouses of Mancheng (Hebei province) and twogreenhouses ofDonggang (Liaoning province) during 2005 and 2006. The control effect ofKangdi 3 to replant diseases of strawberry was evaluated from different aspects.Seven different treatments were involved in the experiment. They were methylbromide full dosage (MB), methyl bromide half dosage (1/2MB), Kangdi 3 low dosage(K1), mid-dosage (K2), high dosage (K3), half dosage of methyl bromide together withmid-dosage of Kangdi 3 (1/2MB+K2), and the untreated control (CK). Among them, thefull dosage of methyl bromide was 50 g/m~2, K1, K2 and K3 represented 75g/m~2, 150 kg/m~2and 225 g/m~2, respectively. All treatments were carried out before transplanting. Aftertransplanting for 60 days, the soil fertilities in two places were investigated. Resultsshowed that the fertilities of the soils in two locations were in a rather high level. Exceptthat in Donggang the available phosphorus content of K3 was higher than MB treatmentand the available potassium content of K2 was higher than K3 treatment, no significantdifferences existed among all other treatments. It indicated that the soil nutrition level ingeneral was not influenced by different treatments.The plant height, plant width, number of roots, length of roots, weight of roots andweight of canopy were measured for the seven treatments in Donggang and Mancheng.Results showed that comparing with CK all the treatments containing Kangdi 3 promotedthe plant growth on some extent. Among them, K3 treatment had the best effect forstrawberry growth, except the weight of canopy in Mancheng and the weight of root inDonggang, all the other criteria of K3 were at the same statistical level of MB.The quality and the yield of strawberry were tested. The results showed that Kangdi 3 could increase the yield and improve the fruit quality. Compared with CK, the treatment ofK3 increased the yield by 237.3ï¼…in Mancheng and 49.6ï¼…in Donggang; the soluble solidin fruit of treatment K3 increased 5.7ï¼…and 8.0ï¼…in Mancheng and Donggang respectively;the fruit rigidity increased 15ï¼…in both locations, the ratio of acid decreased 7.2ï¼…and 9.3ï¼…respectively, and water content decreased 1.5ï¼…and 0.8ï¼…respectively. The K3treatment could improve the fruit quality of strawberry and all the testing criteria had nosignificant difference with MB treatment.The disease indexes on strawberry roots were investigated in Mancheng andDonggang. All treatments containing Kangdi 3 reduced the disease level. Comparing withuntreated CK, K3 treatment significantly inhibited the disease development by 44.2ï¼…inMancheng and 84.7ï¼…in Donggang. Statistically the K3 treatment was at the same level ofMB and 1/2MB+K2 treatments.During the growing stage of strawberry, the populations of fungi in general, Fusariumoxysporum, nematodes in rhizosphere of strawberry, the number of earthworm in soil, thespecies and number of weeds in greenhouse plots were investigated by different methods inMancheng and Donggang. The inhibition rates of K3 were 85.6ï¼…and 92.7ï¼…to fungi,38.8ï¼…and 90.6ï¼…to Fusarium oxysporum, 65.2ï¼…and 45.6ï¼…to weeds in Mancheng andDonggang respectively. The inhibition rates were not significantly different from MBtreatment. Kangdi 3 did not show significant inhibiting effect to the population ofnematodes. The number of earthworms in soils of the two locations was increased by usingKangdi 3, which showed a sound ecological effect.
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