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S. Laywisadkul, C.F. Scagel, L.H. Fuchigami, and R.G. Linderman

and defoliant sprays during nursery production. Our specific objectives were to determine whether susceptibility of field-grown pear trees to P. syringae is related to N concentration in stems and is altered by spraying trees with urea or the

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Benjamin K. Hoover and R.M. Bates

communication). Fraser fir is considered very susceptible to PRR, with minor differences in susceptibility occurring between seed sources ( Frampton and Benson, 2004 ). Canaan fir is closely related to fraser fir and has been reported to survive in soils

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Jerald K. Pataky and Paul M. Richter

to natural infection by U. maydis in field trials were very susceptible when sporidial suspensions were injected into young plant tissues. She hypothesized that resistance or susceptibility was largely a matter of relative accessibility of

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C.C. Reilly, B.W. Wood, and M.W. Hotchkiss

Zonate leaf spot (ZLS) [Cristulariella moricola (Hino) Redhead (C. pyramidalis Waterman and Marshall)] on pecan [Carya illinoinensis (Wangenh.) K. Koch.]—associated with unusually wet weather during June, July, and August—occurred across much of Georgia during Summer 1994. Scott–Knott cluster analysis indicated that 27 of 36 evaluated genotypes exhibited little or no field susceptibility to ZLS. `Moneymaker' exhibited the greatest susceptibility of all cultivars studied, with `Cape Fear', `Elliott', `Sumner', and `Sioux' segregating to exhibit moderate susceptibility. An evaluation of commercial orchards indicated susceptibility of major southeastern cultivars as `Desirable' < `Stuart' < `Schley' < `Moneymaker'. Control of ZLS in commercial orchards using standard fungicide spray strategies appeared to be generally ineffective.

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Ana María Prados-Ligero, María José Basallote-Ureba, Carlos José López-Herrera, and José María Melero-Vara

experienced variable specificity to the markers ( Suárez Bonnet, 2007 ). The widespread use of carnation cultivars described as resistant to FW in SW Spain has resulted in full or partial susceptibility of some carnation cultivars. There are also

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Juan Pablo Fernández-Trujillo, Javier Obando, Juan Antonio Martínez, Antonio Luis Alarcón, Iban Eduardo, Pere Arús, and Antonio José Monforte

in their susceptibility to alternaria rot or cladosporium rots (overall 46% ± 9% and 29% ± 10%, mean ± se , respectively). Rarely, both rots developed internally with mycelium. Cladosporium spp. was occasionally isolated from small spots with corky

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Henry W. Hogmire and Stephen S. Miller

As part of a regional NE-183 project (Multidisciplinary Evaluation of New Apple Cultivars), 23 apple (Malus ×domestica Borkh.) cultivars were evaluated for arthropod pest susceptibility. Incidence or injury data were collected from six foliage and eight fruit pests under field conditions over a four year period (2000–03). Cultivars were ranked based on susceptibility (least to most) to each pest, and rankings were summed for members of the foliage and fruit pest group to develop a susceptibility rating for foliage, fruit and all pests combined. Cultivars with lowest susceptibility to foliage pests included `GoldRush' and `Pioneer Mac', whereas `Yataka' and `Cameo' were most susceptible. For fruit pests, susceptibility was lowest for `Pristine' and `Sunrise', and highest for `Cameo', `Fuji Red Sport #2', and `Gala Supreme'. When both foliage and fruit pests were combined, susceptibility was lowest for `Sunrise' and `Pioneer Mac', and highest for `Cameo'. Some increasingly popular cultivars had high levels of injury from a few pests, including plum curculio and apple maggot on `Ginger Gold', codling moth and oriental fruit moth on `Cameo', and japanese beetle, plum curculio and apple maggot on `Honeycrisp'. A positive and significant correlation was found between day of harvest and percent fruit injury from codling moth/oriental fruit moth and tufted apple bud moth/redbanded leafroller, with later maturing cultivars experiencing higher injury levels presumably due to more exposure to later generations of these pests. Differences among cultivars in pest incidence and injury can be used by growers to improve pest management through cultivar selection, or by making modifications in control programs based on cultivar susceptibility.

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Harry S. Paris, Peter J. Stoffella, and Charles A. Powell

`Striato d'Italia' (cocozelle group) and `Clarita' (vegetable marrow group) summer squash were grown in the greenhouse and field in the presence of sweetpotato whiteflies (Bemisia tabaci Germ.) and their susceptibility to leaf silvering was compared. Silvering was less severe in `Striato d'Italia' in the greenhouse and field.

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Joseph P. Albano and William B. Miller

The susceptibility of seven African marigold (Tagetes erecta L.) cultivars to iron toxicity was assessed. Plants were grown in a greenhouse in a soilless medium and Fe-DTPA was incorporated into the nutrient solution at either 0.018 mmol·L-1 (low) or 0.36 mmol·L-1 (high). Symptoms of Fe toxicity (bronze speckle disorder in marigold characterized by chlorotic and necrotic speckling and downward leaf cupping and curling) developed only in the high-Fe treatment. The concentration of Fe in leaves in the high-Fe treatment was 5.6 and 1.7 times as great as in the low-Fe treatment for `Orange Jubilee' and `Discovery Orange', respectively. Based upon the percentage of plants affected and leaf symptom severity, relative cultivar susceptibility to Fe toxicity was Orange Jubilee > First Lady > Orange Lady > Yellow Galore > Gold Lady > Marvel Gold > Discovery Orange. Chemical names used: ferric diethylenetriaminepentaacetic acid, disodium salt dihydrate (Fe-DTPA).

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Alan R. Biggs and Stephen S. Miller

Twenty-three apple (Malus ×domestica Borkh.) cultivars were tested in the field and laboratory for their relative susceptibility to the white rot pathogen, Botryosphaeria dothidea. Wounded fruit were inoculated in the field at 2 to 3 weeks preharvest with mycelium from 14- to 21-day-old cultures. In the laboratory, detached fruit were similarly inoculated. Fruit were rated for relative susceptibility to the fungus with two criteria: disease severity of attached fruit in the field based on lesion growth (mm/degree-day) and disease severity of detached fruit in laboratory inoculations of wounded fruit (mean lesion diameter after 5 days). Based on the laboratory and field data from 2 years of study, cultivars were classified into three relative susceptibility groups: most susceptible: `Fortune' and `Pristine'; moderately susceptible: `Golden Supreme', `Creston', `Ginger Gold', `Sansa', `Golden Delicious', `Senshu', `Orin', `Sunrise', `GoldRush', `Arlet', `Braeburn', `Cameo', `Enterprise', `Fuji', `Shizuka', `Gala Supreme', and NY 75414; and least susceptible: `Honeycrisp', `Yataka', `Suncrisp', and `PioneerMac'. Compared to previous cultivar rankings, the results of the present study indicate that some new apple cultivars from the first NE-183 planting show greater resistance to Botryosphaeria dothidea than current standard cultivars.