this month in diseases

basil

By A.R. Chase and Margery Daughtrey

Disease

Pathogen

Anthracnose Botrytis blight

Colletotrichum sp.

Botrytis cinerea

Stage of Crop Best Cultural Controls

Any stage

Any stage

Avoid overhead irrigation; keep leaves dry. Rogue out.

Irrigate when leaves will dry quickly.

Cercospora leaf spot

Downy mildew Fusarium wilt

Cercospora sp. Any stage

Use pathogen-free seed. Avoid overhead irrigation; keep leaves dry. Rogue out.

Peronospora sp. Any stage

Any stage

Fusarium oxysporum

Late production

Use pathogen-free seed. Lower relative humidity; provide adequate spacing; use fans.

Use pathogen-free seeds and plugs, as well as new fl ats and potting medium. Disinfest benches between crops.

Phytophthora stem rot

Pseudomonas leaf spot

Pythium root rot

and blight

Rhizoctonia damping-of

Sclerotinia blight

Xanthomonas leaf spot

Rhizoctonia solan

Phytophthora spp. Late production

Pseudomonas

cichorii and others

Pythium spp. Plug

production, primarily

Late in

production, primarily

Early production Sclerotinia sp.

Late spring, near

fi nishing

Xanthomonas campestris

Virus

Impatiens necrotic spot virus

10 GPN May 2010

Plug

production, primarily

Any stage

Irrigate when leaves will dry quickly. Rogue out.

Avoid over-crowding.

Use pathogen-free plugs, new pots and new potting media. Don’t overwater.

Irrigate when leaves will dry quickly.

Use new pots and potting media; use a well-drained growing mix. Do not overwater or overfertilize.

Use new fl ats and potting medium.

This month, we cover diseases of basil, a crop often grown for food use as well as ornamental use. Because herbs are a food crop, we have decided to omit any references to chemical control. Treatments are limited to fungicides not precluded from greenhouse use that are also labeled for use on basil. Thus, controls are largely restricted to the nonchemical portion of integrated pest management: clean seed, containers and growing media, plus careful watering and fertilization — and monitoring for symptoms so that diseased plants may be removed before problems spread.

— A.R. Chase is president and pathologist of Chase Horticultural Research, Inc. and can be reached at archase@chaseresearch. net. Margery L. Daughtrey is senior extension associate at Cornell University’s Long Island Horticultural Research & Extension Center and can be reached at mld9@cornell.edu.

Control thrips. Rogue symptomatic plants immediately.

www.gpnmag.com Page 1  |  Page 2  |  Page 3  |  Page 4  |  Page 5  |  Page 6  |  Page 7  |  Page 8  |  Page 9  |  Page 10  |  Page 11  |  Page 12  |  Page 13  |  Page 14  |  Page 15  |  Page 16  |  Page 17  |  Page 18  |  Page 19  |  Page 20  |  Page 21  |  Page 22  |  Page 23  |  Page 24  |  Page 25  |  Page 26  |  Page 27  |  Page 28  |  Page 29  |  Page 30  |  Page 31  |  Page 32  |  Page 33  |  Page 34  |  Page 35  |  Page 36  |  Page 37  |  Page 38  |  Page 39  |  Page 40  |  Page 41  |  Page 42  |  Page 43  |  Page 44