• Grape downy mildew

  intercellularly, forming haustoria to parasitize mesophyll cells. The latent period (the time from infection to visible symptoms) ranges from 4 to 21 days, depending [...] Leaf symptoms Yellowish to light-green oil spots on the upper leaf surface, often angular and limited by leaf veins White to greyish downy growth on the [...] symptoms Brown to dark lesions on young shoots and tendrils Distorted or stunted shoot growth Increased susceptibility of infected tissue to secondary infections

• Apple scab

  fall off prematurely. The plants’ defence mechanism is to produce corky rings around the lesions to prevent further invasion of tissue by the fungus. Late [...] temperatures this increases to 12-28 hours of leaf wetness for successful infection. Conidia also need water for germination. How to prevent Apple scab Use [...] cycle and appearance of Apple scab Venturia inaequalis overwinters in the form of unripe fruiting bodies in infected fallen leaves or in lesions on twigs

• Black leg of seedlings

  roots are formed or through other similarly damaged spots. On the infected plant, new sporangia with zoospores are formed, that allow the disease to spread [...] germinate and form so-called sporangia from which subsequently zoospores are produced. Zoospores are spores with flagellae, which enable the spores to move through [...] nail. Life cycle and appearance of Black leg of seedlings Pythium belongs to the Oomycetes, a separate group of microorganisms and is therefore not a real

• Damping-off

  roots are formed or through other similarly damaged spots. On the infected plant, new sporangia with zoospores are formed, that allow the disease to spread [...] germinate and form so-called sporangia from which subsequently zoospores are produced. Zoospores are spores with flagellae, which enable the spores to move through [...] with a finger nail. Life cycle and appearance of Damping-off Pythium belongs to the Oomycetes, a separate group of microorganisms and is therefore not a real

• Citrus mealybug

  order to gain an adequate intake of protein, mealybugs must therefore ingest large quantities of sap, getting rid of the excess sugars in the form of honeydew [...] and can be hard to spot. They are smaller than the females, have two pairs of wings and two long tail filaments. Their sole task is to fertilize the females [...] attaches itself to the plant, whereas the females remain mobile throughout their entire development. After the second instar, a male nymph forms a dark brown

• Blight of pepper

  (thick-walled mycelium cells which are resistant to desiccation) or mycelium. Zoospores are formed from the overwintering structures which infect the [...] are spores with flagellae, which enable them to move through water. Infection is usually from the root to the foot, but direct infection of the foot also [...] wetness is required. Dispersal is by wind and rain causes the pathogen to be returned to the soil from infected plants. Dispersal in the soil happens via water

• Angular leaf spot

  conditions are humid, a viscous bacterial exudate forms on the underside of the leaf. This exudate changes to a white film when it dries. Lesions may merge [...] causes small, water-soaked lesions on the underside of the leaf. They enlarge to angular spots, often limited by the small veins. The distinctive feature is [...] types of vascular tissue of the crown can be infected, creating a look similar to that of a Phytophthora fragariae infection. Life cycle and appearance of Angular

• Powdery mildew

  and makes it harder for the fungi to enter the leaves To reduce chances of powdery mildew in greenhouses, it is advised to first ventilate by only opening [...] dispersal of spores over small distances (limited time) mostly happens via workers’ clothing. How to prevent Powdery mildew Use resistant cultivars whenever [...] appear on the upper side of the leaves. Many sweet pepper cultivars react to powdery mildew infection by dropping leaves that are not infected yet. It

• Apple collar rot

  (thick-walled mycelium cells which are resistant to desiccation) or mycelium. Zoospores are formed from the overwintering structures, which infect the [...] are spores with flagellae, which enable them to move through water. Infection is usually from the root to the foot, but direct infection of the foot also [...] wetness is required. Dispersal by wind and rain causes the pathogen to be returned to the soil from infected plants. Dispersal in the soil happens via water

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