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Todd L. Mervosh and James A. LaMondia

The effects of terbacil herbicide on strawberry (Fragaria ×ananassa Duch. `Honeoye') yield and black root rot disease were determined in field plots at two locations in Connecticut over 4 years. Terbacil treatments at up to four times the maximum label dosage caused some temporary foliar chlorosis but did not affect the health of structural or perennial roots and associated feeder roots. Development of secondary root growth (perennial roots) was not influenced by terbacil. Terbacil had no effect on the quantity of lesion nematodes [Pratylenchus penetrans (Cobb) Filip & Schur. Stek.] extracted or the amount of the fungal pathogen Rhizoctonia fragariae Husain and McKeen isolated from strawberry roots. At both locations, R. fragariae was common on plant roots by the fourth year. Terbacil treatments did not affect strawberry yields in terms of number or weight of ripe berries per plot. Our results indicate that terbacil does not contribute to black root rot or decreased yields in `Honeoye' strawberry. Chemical name used: 5-chloro-3-(1,1-dimethylethyl)-6-methyl-2,4-(1H,3H)-pyrimidinedione (terbacil).

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Chrislyn Ann Particka and James F. Hancock

). Many biotic factors have been associated with BRR, with Rhizoctonia fragariae perhaps the most common and widespread throughout the United States and other countries ( Abad et al., 1999 ; D'Ercole et al., 1989 ; Husain and McKeen, 1963 ; Maas, 1998

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Katherine Wine and Marvin Pritts

Black root rot is a devastating, poorly understood disease complex affecting strawberries throughout the world, especially in perennial plantings. Field measurements at 54 sites in New York were made for 113 cultural and environmental variables, and root health was quantified. Root health was negatively associated with wet, compacted soils where plants were grown for several years on flat beds with terbacil herbicide. Pratylenchus penetrans numbers were associated with rotting rots, but not in all sites. Rhizoctonia fragariae and Pythium spp. were usually isolated where black root rot was present, but not always. When strawberry plants were grown in infested soil at warm temperatures (23C), R. fragariae was most commonly isolated, and when grown in the same soil at cool temperatures (5C), Pythium was found. Inoculation of sterile soil with Pythium and/or Rhizoctonia reduced root dry weights, but symptoms were not identical to those observed in the field. Various combinations of pathogenic fungi, nematodes, soil compaction, flooding, low light and terbacil failed to recreate field symptoms in the laboratory. Tolerance rankings of 20 cultivars were different at four field sites. These observations suggest that black root rot can have many causes, and that susceptibility may be stress induced under field conditions.

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Chrislyn A. Drake* and James F. Hancock

Black root rot is a serious disease of strawberry (Fragaria ×ananassa Duch.) that causes the death of feeder roots, the degradation and blackening of structural roots, and an overall decrease in plant vigor and productivity. The causal organisms of black root rot are Rhizoctonia fragariae, Pythium sp. and Pratylenchus penetrans (the root lesion nematode). Each organism alone can cause extensive damage to strawberry roots, but studies have shown that black root rot may be more severe when all organisms are present, indicating there is an interaction between the fungal organisms and the nematode. The current method of control for black root rot is methyl-bromide fumigation; however, methyl bromide is to be phased out by 2005, and it is not very effective in perennial matted-row systems. The objectives of the study are to measure levels of tolerance to black root rot in 21 strawberry genotypes. The genotypes were planted in four blocks each of methyl-bromide fumigated and non-fumigated soil, and were evaluated for crown, runner, and inflorescence number; yield; average berry weight; and root health. `Cavendish', `Kent', `Midway' and `Winona' showed the highest degree of tolerance, while `Jewel', `Mesabi', and LH50-4 (a F. virginiana genotype) were the poorest performers.

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Chrislyn A. Drake and James F. Hancock

Black root rot is a widespread disease of strawberry (Fragaria×ananassa Duchnesne) that causes the death of feeder roots and the degradation of structural roots. The major causal organisms of black root rot include Rhizoctonia fragariae Husain and W.E. McKeen, Pythiumspp. and Pratylenchuspenetrans(Cobb) Filipjev and Schuurmans Stekhoven. The current method of control for black root rot is methyl-bromide fumigation; however, methyl bromide is scheduled to be phased out in 2005, and its effects are short-lived in matted-row systems. The objectives of the study were to measure levels of tolerance to black root rot in 20 strawberry genotypes and to determine which pathogens were present in the soil. The genotypes were planted in four blocks each of methyl-bromide fumigated and nonfumigated soil, and were evaluated for crown number, number of flowers per crown, yield, and average berry weight over two years. The results showed that all three pathogens were present in the field, and that there was a significant genotype × fumigation interaction for yield and crown number in both years. The cultivars Bounty, Cabot, and Cavendish, all released from the breeding program in Nova Scotia, displayed tolerance to the pathogens that cause BRR. Greenhouse studies were conducted using a subset of the genotypes to determine if any one pathogen causes more damage than others, and to determine if susceptibility to a particular pathogen varies between genotypes.

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Chrislyn A. Particka and James F. Hancock

Black root rot (BRR) is a widespread disease of strawberry (Fragari×ananassa Duchnesne) that causes the death of feeder roots and the degradation of structural roots. The major causal organisms of BRR include Rhizoctonia fragariae Husain and W.E. McKeen, Pythium Pringsh., and Pratylenchus penetrans (Cobb) Filipjev and Schuurmans Stekhoven. The current method of control for black root rot is methyl-bromide fumigation; however, methyl bromide is scheduled to be phased out in 2005, and its effects are short-lived in matted-row systems. The objectives of the study were to measure levels of tolerance to BRR in 20 strawberry genotypes and to determine which pathogens were present in the soil. The genotypes were planted in four blocks each of methyl-bromide fumigated and nonfumigated soil, and were evaluated for crown number, number of flowers per crown, yield, and average berry weight over 2 years. The results showed that all three pathogens were present in the field, and that there was a significant genotype × fumigation interaction for yield and crown number in both years. The cultivars Bounty, Cabot, and Cavendish, all released from the breeding program in Nova Scotia, displayed tolerance to the pathogens that cause BRR.

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Marvin P. Pritts

( Rhizoctonia fragariae ), a known pathogen of strawberry, can enhance nutrient uptake and growth under certain conditions by functioning similarly to mycorrhizae ( Scott et al., 2004 ). Plants grown in soils high in P may have low P in leaves if B, essential

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Michelle L. Paynter, Elizabeth Czislowski, Mark E. Herrington, and Elizabeth A.B. Aitken

, Macrophomina phaseolina , Phytophthora species, Pythium species, Rhizoctonia fragariae , and Verticillium species. Crown and root diseases of strawberry are considered a serious problem to strawberry production with 10% of plant death in QLD and up to 50

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Ksenija Gasic and John E. Preece

), black root rot disease complex ( Rhizoctonia fragariae, Coniothyrium fuckelii, Hainesia lythri, Idriella lunata, Pyrenochaeta sp., Pythium spp.), angular leaf spot ( Xanthomonas fragariae ), two-spotted spider mite, cyclamen mite ( Tarsonemus pallidus