Introduction: II existait, en 2001, une très grande disparité géographique dans I'incidence d'utilisation des hormones thyroïdiennes (HT) entre les territoires de centre local de services communautaires (CLSC) au Québec. Comme de tels excès géographiques n'étaient pas liés à une variation dans les pratiques médicales, l‘hypothèse des facteurs environnementaux pourrait expliquer cette situation. Compte tenu que certaines études de type cas-témoins et de cohortes suggèrent la possibilité d'un lien entre I'exposition aux BPC, à des niveaux élevés d'l, au tabagisme et I'accroissement du risque d'hypothyroïdie, I'objectif de cette étude était de vérifier s'il existait une relation entre I'incidence de ('utilisation des HT synthétiques au Québec par territoires de CLSC et la proportion de sujets exposés à ces facteurs de risques via leurs habitudes de vie. Ceci à des fins d'exploration de facteurs qui pourraient expliquer, du moins en partie, la disparité géographique de I'incidence locale d'hypothyroïdie au Québec. Méthodes : Pour ce faire, I'incidence de I'hypothyroïdie fut estimée sur la base de I'utilisation des HT synthétiques par territoires de CLSC. L'exposition aux BPC fut considérée anormalement élevée chez les consommateurs de huit repas de poissons et plus par mois. L'exposition à I'l fut considérée anormalement élevée pour une consommation de trois repas et plus par mois de fruits de mer. La proportion de fumeurs réguliers pour chaque territoire de CLSC fut considérée pour le tabagisme. Les données de consommation d'HT parmi les personnes assurées par le régime public d'assurance médicaments du Québec ont servi à estimer I'incidence de I'hypothyroïdie de 1998 à 2001 chez les hommes pour 154 des 169 territoires de CLSC du Québec et chez les femmes pour 157 territoires. Séparément par sexe, elles ont été mises en relation avec des données sur la consommation de poissons et de fruits de mer (Enquête santé sur les usages et perceptions du Saint-Laurent (1995)) ainsi que sur la proportion de fumeurs réguliers (Enquête sociale et de santé 1998). Les données provenant de ces différentes sources ont d'abord été ramenées sur une base de territoire de CLSC. Les proportions de grands consommateurs de poissons (> huit repas par mois) et de fruits de mer (> trois repas par mois) ont pu être estimées pour une cinquantaine de territoires alors que la proportion de fumeurs réguliers était disponible pour la presque totalité des territoires. Résultats : La proportion de grands consommateurs de poissons, de fruits de mer et de fumeurs réguliers ne sont pas liées au taux d'incidence standardisé d'utilisation d'HT (cas/100 000 personnes de 1998 à 2001) par territoire de CLSC, ni chez les hommes, ni chez les femmes. La relation avec la proportion de fumeurs réguliers est significative pour les deux sexes dans les modèles de régression linéaire multiple (RLM ; hommes : n = 49, p < 0,001 ; femmes : n = 55, p < 0,004). Conclusion : Cette étude écologique ne permet pas d'établir un lien entre la consommation de poissons et de fruits de mer ainsi que le tabagisme et I'incidence de I’hypothyroïdie. L'association significative dans la RLM entre le taux d'incidence standardisé d'utilisation d'HT et la proportion de fumeurs réguliers est visiblement affectée par trois territoires de CLSC de la Côte-Nord qui ont à la fois une forte proportion de fumeurs ainsi qu'un taux élevé d'incidence standardisé d'utilisation d'HT. L'information sur le type d'hypothyroïdie (franche ou subclinique) n'étant pas disponible, il est plausible que cela masque une association entre les variables indépendantes et I’hypothyroïdie franche. II se peut également qu'un seuil minimal d'exposition aux BPC ou aux composés chimiques contenus dans la fumée de cigarette soit nécessaire pour avoir un effet sur la thyroïde. Enfin, l'exposition au sélénium contenu dans le poisson et les fruits de mer pourrait représenter un facteur protecteur contre le développement de I’hypothyroïdie.

Alternaria fruit rot on Minneola tangelos and navel oranges can reach economically important levels in central Arizona. The objective of this study was to test the efficacy of a new fungicide, Headline (BAS 500), for disease management. A trial was conducted in 2000 and 2001 in a commercial Minneola tangelo grove with a history of Alternaria fruit rot. In 2000, nine trees were sprayed monthly from August to December with Headline at a rate of 0.25 lb active ingredient per acre. Another nine trees were not sprayed and served as controls. In 2001, 15 trees were sprayed monthly from November, 2001 to February, 2002 with the same rate of fungicide used in 2000. Another 15 trees were not sprayed and served as controls. Disease severity was evaluated monthly from September to February in each season by counting the number of infected fruit that had dropped from trees. No disease was evident from September through November, when fruit were green. By December the fruit had matured and turned color; additionally, Alternaria fruit rot was first observed. Low numbers of infected fruit were recorded in December and January with higher numbers of infected fruit from non-treated compared to treated trees. In February the mean number of infected fruit from trees treated with Headline and non-treated trees was 2.1 and 3.8%, respectively, in the 2000 trial and 1.9 and 4.5%, respectively, in the 2001 trial. Disease was numerically reduced in both years; however, the difference was only statistically significant in 2001. The findings of this research suggest that Headline could provide meaningful reduction in the incidence and severity of Alternaria fruit rot in Minneola tangelo groves.

This experiment was established in January 2000 in a block of ‘Washington’ navel orange trees at Verde Growers, Stanfield, AZ. Treatments included: normal grower practice, winter low biuret (LB) urea application, summer LB urea application, winter LB urea application plus winter and spring potassium phosphite, winter LB urea application plus summer potassium phosphite, and normal grower practice plus spring potassium phosphite. Each treatment was applied to approximately four acres of trees. For 2000-01, yields ranged from 40 to 45 lbs. per tree, and there was no effect of treatments upon total yield, and only slight effect upon fruit size, grade and quality. For 2001-02, there was a slight effect of treatment upon yield as LB urea led to improved yield, while potassium phosphite led to reduced yield. Normal grower practice was intermediate between these two extremes. For 2002-03, we noted a large increase in yield, however the yield data was lost when the block was inadvertently harvested.

Alternaria rot of citrus is a serious problem in citrus production world wide. In Arizona, the disease is most commonly found in Minneola tangelos and navel oranges grown in Maricopa County. Alternaria rot occurs primarily as a stem-end rot on fruit held in cold storage. However, under optimum conditions the disease occurs as a stylar-end rot in the orchards. In Arizona, the disease can significantly reduce yield, and annual fruit losses have been estimated at 0.5 box per tree. In terms of fruit quality, this disease can be a serious problem for the fresh fruit market as well as for the processing industry because only a small amount of rot imparts a bitter flavor and small black fragments of rotted tissue spoil the appearance of the juice. The application of fungicides is the most common tactic used to reduce losses to this disease. However, to date, no consistent reduction in disease has been achieved through chemical applications. This suggests that additional information relating to the biology of the pathogen and the epidemiology of disease will be necessary for the successful development of a reliable disease management program.

Much of the citrus produced in southwestern Arizona is grown on sandy soils. Because these soils have a low ion exchange capacity, are highly permeable to water, and are prone to nitrate leaching, achieving efficient N management presents a continuing challenge. A field study was conducted on a superstition sand to evaluate the response of lemons to combinations of soil and foliar applied N. Lemon yields significantly increased by soil applied N. Foliar N increased yields of lemons the first harvest at the lower soil N rates. However, there were no other significant responses to foliar N. Overall, there were few meaningful changes in fruit quality to N fertilization. The N content of the leaves increased linearly to soil N application

‘Newhall’ navel oranges on ‘Carrizo’ rootstock were planted in Mar. 1997 at the Citrus Agricultural Center. The objectives of this experiment, conducted during 2000 - 2003, were to i) determine the effects of N rate and fertigation frequency for microsprinkler-irrigated navel oranges on tree N status, and crop yield and quality; and ii) develop Best Management Practices which promote optimum tree growth and production while minimizing nitrate leaching. The trees were equipped with a microsprinkler irrigation system. The experiment was a randomized complete block factorial with N rates of 0, 0.15, 0.30, and 0.45 lb N/tree/year, and fertigation frequencies of weekly, monthly, and three times per year. Each of the ten treatments was replicated five times. The trees were harvested in December or January of each growing season. Fruit were processed through an automatic fruit sizer, and fruit from each plot were further evaluated for fruit quality. Leaf N concentration and fruit yield of 4-6 year old trees were responsive to N rate, but not to fertigation frequency. Fruit quality and packout were not significantly affected by either N rate or fertigation frequency. Fruit yield was optimized at annual N rates of 0.25 lb/tree (four-year-old trees) to 0.35 lb/tree (six-year-old trees) during this experiment. We propose new tissue guidelines for guiding N fertilization of young microsprinkler-irrigated navel oranges.

An experiment was initiated in 2000 to study the feasibility of growing organic lemons in the southwest desert of Arizona. An eight-acre field was selected on Superstition sandy soil at the Mesa Agricultural Research Center to conduct this investigation. Lemon trees were planted at 25 x 25 feet spacing in 1998. The initial soil test in top 6 inches was 5 ppm nitrate-nitrogen and 4.9 ppm NaHCO3-P. Soil pH was 8.7 in the top 6 inches. Four treatments were applied in randomized complete block design repeated four times. The treatments were beef cattle feedlot manure and perfecta, clover and guano from 2000 to 2002, cowpea and guano in 2003, and guano and perfecta, and standard practice treatment. Soil samples were collected from 0-6 and 6-12 inches the first week of March 2003 and analyzed for available nutrients. Results showed a difference for most nutrients in 0 to 6 and 6 to 12 inches between treatments. Nitrate- nitrogen increased significantly from 3.25 ppm in standard treatment to 19.10 ppm in the manure treatment. Similarly, soil organic matter increased from 0.1% in standard treatment to 0.2% in the manure perfecta treatment. Phosphorus level increased significantly from 7 ppm in guano perfecta to 56.5 ppm in manure perfecta treatment. Leaf tissue analysis indicated that nitrate level was influenced by treatment. Both commercial standard and organic treatments were equally effective in controlling citrus thrips, but repeated applications were required. Mite population has been detected at low level with no significant differences observed among treatments.

Much of the citrus produced in southwestern Arizona is grown on sandy soils. Because these soils have a low ion exchange capacity, are highly permeable to water, and are prone to nitrate leaching, achieving efficient N management presents a continuing challenge. Studies were conducted during 1999, 2000, and 2001 to evaluate the response of micro-sprinkler irrigated lemons to N rate (0, 1.8, and 3.6 kg N tree-1 yr-1) and N source (UN32, CAN-17, CN9, and mixed program) on Superstition Sand. Lemon yield increased by N rate during the first and second harvests in 1999, 2000, and 2001. In 1999, yields increased linearly to 3.6 kg N tree-1 yr-1 but in 2000 and 2001 yields were maximized at 1.8 kg N tree-1 yr-1. In 1999 where larger increments of N were applied over a smaller time period relative to the other seasons, UN32 seemed to decrease yields at the highest N rate. There were no significant effects to N source in 2000 and 2001.

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