Downy mildew of broccoli, caused by the fungus Peronospora parasitica, is a perennial disease problem affecting winter broccoli production in Arizona. During 1985-87, potential systemic fungicides were evaluated in the field for disease control. In the 1985-86 season, a period of high disease incidence, lesion development was significantly reduced by fosetyl-Al (44 %), phosphorous acid (42 %), oxadixyl + mancozeb (35 %), chlorothalonil (33 %), metalaxyl + mancozeb (30 %) and metalaxyl + chlorothalonil (28 %). During the 1986 -87 growing season, disease incidence was low and lesion development was significantly reduced by phosphorous acid (82 %), fosetyl -Al or oxadixyl + chlorothalonil (77 %), metalaxyl + chlorothalonil (68 %) and chlorothalonil (54 %). Fosetyl-Al, phosphorous acid and oxadixyl were as effective as currently available fungicides ( metalaxyl and chlorothalonil) for control of downy mildew of broccoli in Arizona.

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Downy mildew of broccoli, caused by the plant pathogenic fungus Peronospora parasítica, can be found every year in many broccoli fields in Arizona. The severity of the disease is affected by the occurrence and duration of weather conditions favorable for disease development. During the 1990-91 vegetable season in western Arizona, different fungicides and rates of materials were evaluated in the field for disease control. Ridomil /Bravo and Bravo, which are currently registered for use on broccoli to control downy mildew, and Aliette, which is currently not registered for use on this crop, provided significant disease control compared to untreated plants. Rovral and Topcop did not control downy mildew on broccoli.

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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 control in field trials conducted during 1994 and 1995. Downy mildew did not occur in the 1994 trial. In 1995, disease was moderate and all tested fungicides provided significant disease control compared to no treatment at all. Three new fungicides, Fluazinam, Dimethomorph, and ICIA-5504, show promise as potential new materials for control of downy mildew on broccoli.

Second year field studies continued to evaluate and determine efficacy and safety of postemergence herbicides for broccoli weed control. Goal® 2XL. a newly introduced formulation of oxyfluorfen. severely injured broccoli after application. London rocket (Sisvmhrium irio) control was not acceptable at less than 80%. Pvridate (Lentagran®) and clopyralid (Stinger®) were relatively safe on broccoli but did not affect London rocket.

Two pyrethroid insecticides, fenpropathrin (Danitol®) and bifenthrin (Capture®), were evaluated in several combinations with other insecticides for whitefly control in broccoli and demonstrated good efficacy to reduce eggs and immature stage insects. At one week after the second of three applications, Danitol® or Capture® plus methamidaphos (Monitor®), acephate (Orthene®), or endosulfan (Thiodan®) significantly reduced egg counts relative to the untreated check.

Three commonly used herbicides for use in broccoli were effective when applied alone or in combinations as a preplant incorporated (PPI) or a preemergence (PE) application. DCPA (Dacthal®) at 10.0 lb product/A PE gave acceptable control of most weeds. Trifluralin (Treflan® SEC) at 1.0 pt/A and bensulide (Prefar® 4EC) PPI were also effective but mustard weeds were not adequately controlled. Combinations of the herbicides at lower rates did not provide any advantage in improving weed control efficacy.

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 1997 field trial. A moderate degree of downy mildew developed by crop maturity. All tested compounds except Trilogy provided significant reductions in the severity of disease compared to no treatment at all. Several products not presently registered for use on broccoli show promise as potential new materials for disease management.