A number of foliar fertilizers were evaluated for their effects on yield and quality of both cantaloupes and honeydews. None of the treatments or treatment combinations resulted in statistical increases or decreases for numbers of cantaloupes or honeydews when compared with the untreated check. A highly significant increase of one treatment regimen (which contained calcium) was noted for cantaloupe weights when compared with the untreated check. Statistical differences were not noted for honeydew weights for this treatment although it also resulted in highest calculated weights of honeydew/area of treatments evaluated. All treatments resulted in numerically higher brix for cantaloupes than the untreated check, thought to be a response to pounds of melons/unit area as the untreated check had the least cantaloupe weight. No differences were noted for cantaloupe seed cavity diameters.

Phytophthora blight of peppers (Capsicum annuum) is caused by the oomycete pathogen Phytophthora capsici. In Arizona, the root and crown rot phase of the disease initially can appear on plants early in the growing season in areas of the field where soil remains saturated with water after an irrigation. Disease severity can increase dramatically due to summer rains during July and August in the southeastern Arizona production area. The efficacy of the systemic fungicide mefenoxem (Ridomil Gold)) for control of Phytophthora blight on pepper has been documented; however, in many pepper production regions, populations of the pathogen insensitive to this fungicide have developed. Other chemistries, including dimethomorph (Acrobat) as well as two new fungicides in development (Ranman and TM-459) have activity on some species of Phytophthora and associated diseases on crops other than pepper. The objective of the following trials was to evaluate and compare the effects of soil drench treatments with Ridomil, Acrobat, Ranman and TM-459 alone, as well as in combination treatments on subsequent development of root and crown rot on chile pepper plants grown in soil naturally infested with P. capsici. Three separate trials were conducted in the greenhouse. Usually, the top fresh weight of plants treated with an appropriate amount of Ranman, TM-459, or Acrobat did not differ from plants grown in sterilized soil. On the other hand, the top fresh weight of plants treated with Ridomil Gold often was not significantly different from plants grown in untreated infested soil, implying that this soil contained a population of Phytophthora capsici that is insensitive to this fungicide. These trials suggest that soil application of Ranman and TM-459 could effectively inhibit the development of Phytophthora root and crown rot on chile peppers grown in soil infested with Phytophthora capsici.

To determine growth and development patterns of irrigated melon (Cucumis melo L.) plants as a function of heat units accumulated after planting (HUAP), as well as to develop a general irrigated cantaloupe plant development model as a function of HUAP. Fifteen commercial melon fields managed by cooperator-growers were selected at five locations in Arizona from 2003 through 2006 to conduct phenological monitoring studies. Basic plant growth and development measurements were collected at phenological stages that corresponded to pre-bloom, early fruit set, early netting, and physiological maturity. Results indicate that in general, growth and development stages of melons occurred with a high degree of consistency as function of HUAP in all sites. Varietal differences did not appear to have large effects on phenological development. Also, a general irrigated cantaloupe plant development model as function of HUAP for all sites and varieties was obtained. The purpose of this phenological baseline or model is to assist growers in predicting and identifying critical stages of growth for crop management purposes. Early bloom occurred at 357 ± 41 HUAP; early fruit set at 619 ± 81 HUAP; early netting at 820 ± 82 HUAP; and physiological maturity (of primary fruit set or crown fruit) was identified to occur at 1297 ± 128 HUAP.

Sclerotinia drop of lettuce, caused by the pathogenic fungi Sclerotinia minor and S. sclerotiorum, is a serious disease in most regions were this crop is grown. Conventional fungicides, such as Rovral (iprodione) and Endura (boscalid), are usually applied after lettuce is thinned and once more 2 to 3 weeks later. Two biological products, Contans (Coniothyrium minitans) and Serenade (Bacillus subtilis), are also available. In earlier field trials conducted from 2001 to 2004 in the presence of S. minor, the mean reduction in disease by Contans, Serenade and Endura was 36, 21 and 51%, respectively. The main objective of the current study was to determine the efficacy of the biological products Contans and Serenade, applied alone or in combination with each other or the conventional fungicide Endura, within a biologically intensive integrated pest management system for Sclerotinia drop on lettuce caused by S. minor. The study was conducted at the The University of Arizona, Yuma Valley Agricultural Center. Sclerotia of Sclerotinia minor were produced in the laboratory. Lettuce ‘Winterhaven’ was seeded and sclerotia were applied to the plots on Nov 14, 2005 and the final disease assessment at plant maturity was made Mar 13, 2006. There was a high degree of variability among the replicate plots for each treatment in this trial, as well as an overall low disease incidence, which made statistical comparisons of data difficult. The only treatment in this trial that significantly lowered disease incidence compared to nontreated plots was an initial application of Contans at seeding followed by Endura at thinning. This study was established in a field containing well-draining loam soil, which combined with the lack of any rainfall and the use of furrow irrigations in January and February, which kept the tops of beds dry, likely contributed to the excessive variability and low incidence of disease.

A series of replicated trials were conducted during the winter season of 2003 and 2004 to investigate the effect of pre-harvest applications of cytokinins on yield and postharvest quality of intact and fresh-cut lettuce. We report here only those results obtained at harvest. Cytokinins products were applied at different frequency and rates. The crops in the different trials were under different cultivation programs, including different nitrogen fertilization rates. Figures showing the performance of each individual cytokinin product versus the corresponding untreated controls are provided. Results obtained are mixed even for the same cytokinin product, however, some trends were observed. With the exception of products that also contain other plant growth regulators in their formula, high rates (or multiple applications) of the cytokinin products resulted in no effect or even in negative results. For example applications of Cytokin® did not improve yields as was the case with Cytoplex®, from the same manufacturer, under different conditions. The results from this study suggest that lettuce plants can respond to cytokinin applications, but factors to enhance positive response still need to be studied further. Single applications appear to be the most effective program for products containing only cytokinins, while products such as Cytoplex® can increase yield with multiple applications. A discussion addressing the different results obtained with nitrogen rates and the cytokinin products in yield and quality is included.

The effect of pre-harvest application of Extend®, a newly developed second generation harpin product, on shelf life of fresh-cut lettuce was investigated. The lettuces were grown in locations A: Watsonville, CA; B: Cedarville, NJ; and C: Yuma, AZ, and treated five days before harvest at 30, 60 and 90 ppm (2,4 and 6 oz/acre in 50 gal/acre). Lettuce processed and bagged was stored at 34-37°F and evaluated for quality for 20 days. Lettuce from trial A treated with 60-90 ppm harpin consistently had a better overall quality and lower microbial population than the control. Results from trial B showed no differences among treatments. In trial C, microbial population was lower and visual quality higher in lettuce treated at 60 ppm than the control during early stages of storage. Overall results are mixed but it was revealed that a field application of harpin can improve quality of fresh-cut lettuce under conditions that need to be determined.

In a continuing work, the effect of moisture conditions on yield and microbial quality of Iceberg lettuce was investigated. Iceberg lettuce cv. Sahara grown at the University of Arizona Yuma Agricultural Center was evaluated for yield, microbial population and postharvest quality either following different irrigation termination schedules or before/after a rainfall event. We report here microbial population data with treatments including early (16 days before harvest), middle (8 days before harvest) and late (4 days before harvest) irrigation termination. Lettuce receiving the last irrigation 4 days before harvest showed increased weight but had higher microbial population than other treatments. The effect of moisture prior to harvest on quality was further evaluated with lettuce harvested before and after a rainfall event. Increased aerobic bacteria population of over 1 log CFU/g for outer leaves and over 2 log CFU/g for head leaves was observed after rain. The results from this study suggest that managing moisture conditions at harvest is important to enhance quality of lettuce.

The effect of pre-harvest foliar application of calcium on yield and postharvest quality of whole and fresh-cut cantaloupe melons was investigated. The calcium product (Nutrical®) was applied five times before harvest to a melon field at 2 quarts/acre with a volume of 50 gallons/acre. The supplemented calcium increased by over 10% the weight of melons and increased external firmness at harvest but soluble solids was lower in treated melons than in the control. After 21 days of storage at 40 - 45 °F however, there was not difference in quality factors. Melons were processed in cubes and packaged in plastic lidded containers. The overall quality of calcium treated cubes was better after 5 and 10 days of storage. Juice leakage was also higher in the control than in the treated fruits after 5 days. After 10 days the L* values were lower in the control than in the treated fruits indicating that the tissue was darker in the control, which was an indicative of more water soaked tissue. In further trials conducted the following Spring the results obtained at harvest showed differences only in weight of melons that underwent water stress. The overall results in different experiments in the Yuma area indicate that application of foliar calcium can increase yield of melon crops, notably, when the plants undergo environmental stress.

Downy mildew of broccoli, cauliflower and cabbage is caused by the oomycete pathogen Peronospora parasitica. Cool moist environmental conditions favor the development of downy mildew on these crops. Several fungicides were evaluated individually or combined with another material (applied as a mixture or in a rotational program) for control of this disease on broccoli in the 2004- 05 growing season. Several treatments provided the most efficacious degree of disease control, including Maneb, Reason+Bond alternated with Aliette, Ranman+Maneb+Silwet L-77, Ranman+Silwet L-77, Forum+Maneb, Forum+Penetrator Plus, Reason+Bond alternated with Maneb, PREV-AM +Formula 1, Ranman+Aliette+Silwet L-77, Acrobat+Maneb, Aliette and Phostrol.

To determine growth and development patterns of irrigated green chile plants as a function of heat units accumulated after planting (HUAP), as well as to develop a general irrigated chile plant development model as a function of HUAP. Field experiments were conducted in 2004 and 20055 at Sunsites in Cochise County, AZ (about 4,000 ft. elevation) and at the Massey Farm in the Animas Valley, NM (about 4,392 ft. elevation). Basic plant growth and development measurements were collected routinely and important phenological stages that corresponded to first bloom, early bloom, peak bloom, physiological maturity, and red harvest were identified and recorded. Results indicate that among all sites, all varieties have performed similarly in relation to HU accumulation patterns and preliminary plant phenology models are under development in this program. The primary difference between sites was that at Sunsites varieties tend to reach a 50/50 (green: red chile) ratio at 2900 HUAP and for Animas valley; this same ratio was reached at 3200 HUAP. Also, a general irrigated green chile plant development model as a function of HUAP for all sites and varieties was obtained. The purpose of this phenological baseline or model is to assist growers in predicting and identifying critical stages of growth for crop management purposes. First bloom occurred at 1369 ± 72 HUAP, early bloom at 1667 ± 79 HUAP, peak bloom at 1998 ± 84 HUAP; physiological maturity at 2285 ± 159 HUAP, and red chile harvest was identified to occur at 3295 ± 216 HUAP.