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Angular Leaf Spot

Angular Leaf Spot

Pseudomonas syringae pv. lachrymans

Bacterialalso: Angular leaf spot

A bacterial disease of cucumbers and other vine crops that cuts small, angular, vein-bounded spots into the leaves, which dry and drop out to leave a shot-hole, tattered look. Spread by splashing water in warm, wet weather, it also spots the fruit and rides in on seed, and it is most troublesome on cucumber and melon.

🔎 How to spot it

Look for small water-soaked spots on the leaves that turn brown or straw-colored and are angular, boxed in by the leaf veins rather than round. In humid mornings the spots may ooze a milky bacterial droplet that dries to a white crust on the underside. The dead centers fall out, leaving ragged holes, and small round water-soaked spots can appear on the fruit.

🥀 Damage it causes

Leaf spotting and the holes left as spots drop out reduce the leaf area and can brown and kill heavily infected leaves, weakening the plant and lowering yield. Fruit spots blemish the crop and can open the fruit to soft rots. Cucumber and melon are hit hardest; resistant cucumbers limit it.

🔬 What causes it

Angular leaf spot is caused by the bacterium Pseudomonas syringae pv. lachrymans, which comes in on infected seed and survives on crop debris. It spreads by splashing rain, overhead watering, and handling wet plants, and enters through pores and wounds. Warm, wet, humid weather and prolonged leaf wetness drive it.

🛡️ Prevent it

Start with certified disease-free seed and rotate cucurbits so two or more years pass before they return to a spot. Do not work among or harvest wet plants, water at the base rather than overhead, and space and trellis for fast drying. Clean up debris at season end, and grow resistant cucumber varieties, which are widely available.

🧯 If it is already here

There is no cure once plants are infected, so remove badly affected debris, keep the foliage dry, and avoid handling wet plants so you do not spread the bacteria. Preventive copper sprays can protect healthy tissue in wet spells but give only limited help; follow the label. Resistant varieties and clean seed do far more than spraying.

💡 Good to know

The angular, vein-bounded spots that dry and fall out to leave a shot-hole pattern set this apart from the rounder fungal leaf spots, and the milky ooze on a humid morning confirms it is bacterial. Because it is seed-borne and splash-spread, clean seed, rotation, and keeping hands and tools off wet vines are the key defenses.

🌱 Plants it affects

104 plants in the library can be affected by this problem

Acorn SquashAdzuki Bean🍓Albion StrawberryAmethyst Falls WisteriaAnnabelle Smooth HydrangeaAnnual VincaArizona Sun Blanket FlowerArmenian CucumberAtlantic Giant PumpkinBecky Shasta DaisyBitter MelonBlack BeanBlack Beauty Zucchini🍉Black Diamond WatermelonBlue Lake Green Bean🥒Boston Pickling CucumberBroad Windsor Fava BeanBrunneraButtercup SquashButternut SquashCannellini BeanCantaloupeCarolina JessamineCasaba MelonCascara SagradaCharleston Gray WatermelonCinderella PumpkinCleyeraClimbing HydrangeaCornelian CherryCostata Romanesco ZucchiniCranberry BeanCrenshaw MelonCrimson Cherry RhubarbCrimson Sweet WatermelonDelicata SquashDiabolo Ninebark🥒Diva CucumberEarly Amethyst BeautyberryEndless Summer Hydrangea🥒English CucumberEvergreen HuckleberryFeather Reed GrassFordhook 242 Lima BeanFountain GrassGalia MelonGateway Joe Pye WeedGoldflame SpireaGoldsturm Black-Eyed SusanHoneoye StrawberryHoneydew MelonHubbard SquashHummingbird SummersweetJack-O-Lantern PumpkinJapanese Pieris🍉Jubilee WatermelonJune-Bearing StrawberryKabocha SquashKentucky Wonder Pole BeanKidney BeanKirby CucumberKobold Blazing StarLemon CucumberLily of the ValleyLimelight Panicle HydrangeaLingonberryLynwood Gold ForsythiaMajor Wheeler Trumpet HoneysuckleMarketmore CucumberMedlar🍉Mini Love WatermelonMoerheim Beauty Sneezeweed🍉Moon and Stars WatermelonMung BeanNatchez Mock OrangeNavy Bean🍉Orangeglo Watermelon🍓Ozark Beauty StrawberryPattypan SquashPersian CucumberPickling CucumberPinto Bean🌱Provider Bush BeanQuaking AspenRed Noodle Yardlong BeanRomano BeanRoyal Heritage Lenten RoseSalalScarlet Runner Bean🍓Seascape StrawberrySheffield Pink Garden MumSnow Queen Oakleaf HydrangeaSpaghetti SquashSpeedwellSugar Baby Watermelon🎃Sugar Pie PumpkinSuyo Long CucumberTennessee Red Valencia PeanutTexas Scarlet Flowering QuinceTromboncino Squash

For educational and informational purposes only. Disease management advice is general guidance drawn from university cooperative extension sources; always identify a problem positively and read and follow the label on any product before use, especially around food crops, children, and pets.