NC State and USDA Cucumber Disease Handbook

Angular Leafspot (Pseudomonas syringae pv. lachrymans)


Pseudomonas syringae pv. lachrymans (Smith and Bryan) Carsner.

Culture Description:

On tetrazolium chloride agar (TZC) magenta bacterial colonies are formed.

Microscopic Description:

Gram negative, non-spore forming rods (0.8 x 1-2 microns); motile with 1-5 polar flagella.


P. H. Williams; Plant Pathology Department; University of Wisconsin; 1630 Linden Drive; Madison, WI 53706.

Relative Stability:

No reports of change in pathogenicity. No races known.


No information.

Storage and Retrieval:

On tetrazolium chloride agar (TZC) bacteria can be maintained for 3 months at 4°C. In sterile distilled water bacteria remain viable one year. To retrieve aseptically remove a single colony from the agar or a loop full of bacteria from the water and streak on TZC. Incubate at 20-24°C.

Inoculum Increase:

Aseptically put a single colony from TZC agar in a 125 ml Erlenmeyer flask containing 50 ml Husain-Kelman (HK) broth. Place the flask on a rotary shaker at 28°C for 20-24 hr.

Inoculum Preparation:

Make a 1:19 dilution of the bacterial suspension in 0.01 M phosphate buffer.


Optical density at 625 nm is approximately 0.1.

Inoculum Distribution and Delivery:

Dip a gloved fingertip into the inoculum and spread the inoculum on the lower surface of the cotyledon. Repeat for each cotyledon inoculated.


Cucumis sativus L., cucumber.

Source of Resistance:

PIs reported to contain some resistance: 169400, 264664, 267086, 267745, 257486, and 137848.

Differentials – Controls:

Susceptible check Wisconsin SMR 18. Resistant check Gy 14.

Growth of Host:

Cucumber seeds are sown in steam sterilized coarse grade vermiculite in wooden flats (52 x 36 x 7 cm). Each flat contains 10 rows, 25 seeds/row. Resistant and susceptible checks are sown in row 6. The flats are placed on a heated germination bench. Vermiculite temperatures of 32°C insure rapid and uniform germination. Newspaper on top of the flat prevents cooling by evaporation. Newspaper is removed when seeds germinate.

Tissue Age:

Inoculate cotyledons 3-4 days after emergence when cotyledons are expanded.

Postinoculation Environment:

Incubate in the dark for 48 hr at 20 C and 100% relative humidity. Subsequently place plants in greenhouse 24-32°C.

Disease Response:

Plants are rated as resistant, intermediate, or susceptible 6-8 days after inoculation. Resistant plants develop necrotic tan lesions. Intermediate plants have tan lesions with a yellow green border. Susceptible plants have elongate irregular lesions with yellow margins.

Multiple Inoculation:

Simultaneous inoculation with anthracnose, downy mildew or bacterial wilt. Subsequent inoculation with cucumber mosaic virus (CMV) and powdery mildew.

Saving Host:

Resistant, intermediate, and susceptible plants can be transplanted to steam sterilized soil.

Procedures Developed by:

Paul H. Williams and Mary J. Palmer
Department of Plant Pathology
University of Wisconsin
1630 Linden Drive
Madison, WI 53706 USA

Additional Tips:

For best results, test seedlings at 3-4 leaf stage. Inoculate with mist sprayer under newer leaves. Incubate at 100% RH, 20-25°C 1 day (dark), then 100% RH, 14°C 4-6 days (lights on).