Eleven treatments were applied for sweetpotato whitefly B- biotype control. Best control (62.4%) was evidenced by the Ambush + Thiodan treatment, which had fewest nymph numbers 8 days post treatment and had larger plant sizes (46.3%) 14 days post treatment than the untreated check. Plants in plots receiving treatments including Thiodan and/or Lorsban were also at least 20% larger than the untreated check. Fewest number of adult whiteflies two days post treatments were noted in the Thiodan + M-Pede treatment. Certain treatments increased whitefly numbers.

The new insecticide Imidacloprid (NTN 33893), which is currently being developed for use on vegetable crops, was evaluated on broccoli for control of aphid species. Studies conducted in the spring of 1991 showed that this material applied postemergence as a granular formulation was extremely effective in preventing aphid colonization throughout the season. Aphid control and broccoli yields were significantly greater in plots treated with Imidacloprid. Due to low numbers of aphids in 1992, we were unable to detect differences in aphid numbers between Imidacloprid treatments and the untreated control.

No description available.

No description available.

An exploratory field study provided results of postemergence herbicide weed control efficacy and broccoli tolerance. Pyridate (Tough®), clopyralid (Stinger®), and oxyfluorfen (Goal®) did not cause any crop stand reduction compared to bentazon (Basagran®) that completely reduced the broccoli stand. Tough and Goal at the lower rates tested caused marginally acceptable broccoli injury. Goal effectively controlled pigweed species (Amaranthus sp.), groundcherry (Physalis wrightii), and purslane (Portulacç oleracea). Tough gave good control of pigweed and purslane but not groundcherry. Stinger was safe on broccoli and marginally controlled groundcherry. In a second field study, Tough and Goal were evaluated for cheeseweed control. Goal marginally controlled cheeseweed at all rates tested and caused marginally acceptable injury at the two lowest rates. Tough was relatively safe at the lower rates but did not adequately control the cheeseweed.

Exploratory field studies conducted in broccoli showed that clomazone (Command®) and isoxaben (Gallery®) were extremely phytotoxic to broccoli when applied preemergence (PREE) on the soil surface after planting. Both offered good weed control of the weeds present. Napropamide (Devrinol®) caused moderate crop injury and marginally acceptable weed control.

Downy mildew of broccoli is caused by the plant pathogenic fungus Peronospora parasitica. Cool damp weather with high humidity is highly favorable for sporulation, dissemination of spores, and infection by this pathogen. The severity of disease is affected by the duration of weather conditions favorable for disease development. Potential new fungicides were evaluated for disease management in a field trial conducted in 1996. Disease pressure was moderate and all tested fungicides except Ridomil MZ 72 and one Ciba G + Mancozeb treatment significantly reduced the number of downy mildew lesions on leaves compared to plants not treated with a fungicide. The level of disease reduction provided by all chemical treatments was equivalent to that given by Aliette and Bravo, two fungicides currently available for control of downy mildew on broccoli.

Nitrogen (N) status of vegetable crops is often monitored by analysis of dried plant tissues. However, dry tissue analysis often causes a significant delay between sampling and analysis. This study was conducted to examine the accuracy of a portable nitrate meter for determining petiole sap nitrate (NO₃) concentrations in broccoli (Brassica oleracea L. Italica group cv. Claudia) and cauliflower ( Brassica oleracea L. Botrytis group, cv. 'Candid Charm'). The relationship between NO₃-N concentration in fresh petiole sap and in dried petiole tissue was Studied for these crops in southern Arizona during the 1993-94 and 1994-95 winter growing seasons. Experiments were factorial combinations of 3 irrigation rates and 4 N rates, both ranging from deficient to excessive. Petioles were sampled throughout each season, and were split for sap and dry tissue analysis. A linear correlation was obtained between the two measurements in both seasons, with no consistent effect due to irrigation treatment or crop maturity. The regression coefficients did not differ among seasons. Regression equations were derived to convert petiole sap nitrate concentrations to dry tissue nitrate concentrations. These equations can be used to relate sap test measurements to existing guidelines for NO₃-N concentrations in broccoli and caulker petioles. These results suggest that the quick sap test, using the portable nitrate ion meter, is a valuable technique for monitoring N status of broccoli and cauliflower.

Field experiments were conducted during the 1995-96 winter growing season at The University of Arizona's Maricopa Agricultural Center to determine the response of broccoli and cauliflower to a factorial arrangement of water rates and nitrogen (N) fertilizer rates. Both the broccoli and cauliflower experiments were randomized complete block factorial designs with three water levels (deficient, optimum, and excessive), four N fertilizer levels (deficient, suboptimal, supra optimal, excessive), and four replications. Drip tubing was buried at a depth of eight inches along the midline of each planting bed. Irrigation was applied daily as needed to maintain the predetermined target soil water tension levels and N fertilizer (urea ammonium nitrate solution) was applied in 4 or 5 split applications. Broccoli spears and cauliflower curds were harvested weighed and graded according to prevailing commercial practices. The optimum marketable yield of broccoli of 4.6 tons/acre was achieved with a total application of 18.9 inches of water and 267 lbs. N/acre. The optimum marketable yield of cauliflower of 9.5 tons /acre was achieved with a total application of 18.5 inches of water and 178 lbs. N/acre. For both crops a nitrogen deficiency had a greater negative impact on marketable yield than either deficient or excessive water application. Optimum marketable yields, earliness and head quality for both crops were achieved when the average soil water tension level for the entire season was maintained at about 10 cbars (or 13 cbars uncorrected gauge reading).

No description available.