Dark leaf spot

Cabbage root fly can be a problem and treatments will be required from April onwards. Aphids, caterpillars, cutworms, pollen beetle, cabbage stem weevil and slugs all attack broccoli. Damping off and wirestem can be a problem at the seedling stage. Club root, downy mildew, dark leaf spot, ring spot, white bhster and spear rot can all be a problem in the field. 

Oats Dark leaf spot, speckle blotch S. avenae Leptosphaeria avenaria... 

Stems and leaf undersides with dusty, dark brown spots. Cause Rust. This fungus develops quite rapidly, so leaves must be monitored for initial spotting. Rust-resistant snapdragons are now available and should be used whenever possible. However, they don t eliminate the problem. 

Fruit with small, dark, sunken spots or cracks on skin. Cause Bacterial leaf spot. This disease, common in the Southeast, is very difficult to control. Plant resistant cultivars, including Alfred , Curtis , Harcot , Hargrand , and Harlayne . For more information, see Fruit with small, dark, sunken spots or cracks on skin on page 166. 

Grass blades have dark spots. Causes Leaf spots leaf blights. Several fungi cause... 

Leaves with dark or water-soaked spots. Cause Various bacterial or fungal leaf spot diseases. Destroy badly spotted plants or leaves. Thin plants to increase air movement, and a oid wetting leaves when watering. Prevent rroblems by keeping plants well-fed. 

Dark brown spots with concentric rings, usually appearing on older leaves first, are caused by Alternaria leaf blight. As the disease progresses, leaves curl down and eventually drop off. Fruit infected with this disease has brown, concentrically ringed, sunken spots. Prevent problems by planting resistant culti-vars such as Earligold , Pulsar , and Saticoy . 

Water-soaked spots that turn gray, die, and drop out leaving shotholes are caused by angular leaf spot or scab. Fruit infected with angular leaf spot has small, cracked, white spots. Scab causes fruit with sunken, brown spots with a gummy ooze, and damage is worst in cool, moist weather. Pale, round leaf spots with dark margins are caused by Cercospora leaf spot. 

Fruit with small, dark, sunken spots or cracks on skin. Cause Bacterial leaf spot. 

Leaves with gray-brown spots. Cause Cercospora leaf spot. This fungal disease only occurs in very warm climates. Spc its develop a frog-eye appearance with ligm centers and dark edges. Spray plants with copper as soon as symptoms appear to prevent further syrrip-tom development. Presoak seed in a 10 percent bleach solution and plant resistant cultivars, such as California Wonder , to prevent problems. 

Canes with dark blotches sideshoots may wilt and canes may die. Cause Anthracnose. Centers of 1. leaf spots M A may dropout. ... 

Cause Alternaria leaf blight. Dark brown spots with concentric rings usually appear on older leaves L first also on fruit. 

If the patches develop into circular, dark spots with light centers peppered with dark specks, suspect Septoria leaf spot, another fungal disease. Older leaves are affected first. Spray plants with copper to prevent further symptom development. Spraying transplants with an antitranspirant may help prevent Septoria. However, don t spray with antitranspirant when tomatoes are blooming heavily. 

Thyme is normally quite problem-free. Dark spots on leaves are caused by fungal leaf spot. Spray foliage with fish emulsion or sulfur to prevent the spread of mild infections. Tan or red blisters on leaves are caused by rust, a fungal disease. Destroy infected leaves and avoid wetting leaves to prevent its spread. See the Herbs entry beginning on page 116 for other possible problems. 

Sphaerulina leaf spots These usually are less than 1cm in diameter and initially black in color with their centers turning white enclosed by dark margin in mature lesions. The disease is thought to be caused by the Ascomycete Sphaerulina spp. (Gerlach, 1988). The disease is most prevalent in a warm, moist environment such as that of Samoa and is less common in the cooler and drier climate of Tonga. 

Bacterial leaf spots is a disease affecting lettuce plants caused by Xanthomonas campestris pv. vitians, recently reclassified as X. hortorum pv. vitians [74]. This disease does not normally produce severe losses [75], but outbreaks occur during periods of heavy rainfall [76]. The leaves of infected plants show translucent, water-soaked brown lesions that become dark with age. These types of symptoms, and the fact that the bacterium is generally not isolated from the chlorotic halos surrounding the dead tissues, suggest the involvement of toxic compounds in the disease developments. Two phytotoxic metabolites were isolated from the culture filtrates of X h. pv. vitians, which were identified as 3-methylthiopropanoic and -methylthiopropenoic... 

Cool and damp Frogs, toads, salamanders, beetles, and hoverflies may all make use of a cool, dark, probably damp site make a leaf mold pile see pp.44-45) or leave a pile of logs in a sheltered spot for them to nest in. 

Symptoms First symptoms are a white spotting of leaves caused by the feeding of adult females. Narrow white tunnels appear between the upper and lower leaf surface. These later widen and meander toward the leaf midrib. After 2-3 weeks, small dark bumps can be seen on the lower leaf surface. 

Fig. 5.17. Leaf scab dark spots which go on to produce spores.

Figure 1 Exploding diagram of the photo synthetic apparatus of a typical higher plant. The first expansion bubble shows a cross-section of a leaf, with the different types of cells the dark spots are the chloroplasts. The second bubble is a chloroplast the thylakoid membranes are the dark lines, the stroma is the stippled area. The third bubble shows a grana stack of thylakoids. The fourth bubble shows a schematic picture of the molecular structure of the thylakoid membrane, with a reaction center flanked by anterma complexes. (Ref. 1. Reproduced by permission of Blackwell)...

Leaves and flowers deformed, yellowish small, tarlike spots on undersidies. Cause Lace bugs. These small pests with lacy wings cause yellow-brown le lf spots. Dark brown droppings on lower leaf surfaces confirm their activity. Remove debris in spring and fall to deter overwintering. For severe problems, spray superior oil, insecticidal soap, or pyrethrin. 

Leaves pale and mottled. Cause Lace bugs. These /s - A", dark-colored bugs have lacy wings. They feed on the undersides of leaves and deposit small black spots of excrement. Severe infestations can cause early leaf drop. Control by spraying leaves with superior oil or insecticidal soap. 

Dill is rarely troubled by pests or diseases. Virus-infected leaves are dw ed and deformed and abnormally colored. Destroy infected plants and control leafhoppers as they spread viruses. Leaf blight causes dark spots with yellow edges. To control this fungal disease, spray plants with fish emulsion or in severe cases, with sulfur. See the Herbs entry beginning on page 116 for other possible problems. 

Flowers deformed leaves and petals with white flecks. Cause Thrips. Gladiolus thrips are a very destructive common pest. These V25", yellow to black, flying insects feed by rasping petals and leaf surfaces, leaving silvery spots and streaks. They hide under leaf sheaths and inside flowers. Other symptoms are partial bloom, failure to bloom, and shriveling. Thrips wastes may appear as black spots on the undersides of leaves. Infested corms are dark, sticky, and rough. 

Parsley has few problems. Handpick leafeating caterpillars or spray plants with BTK. Dwarfed or abnormally crinkled leaves can be caused by viruses. Destroy infected plants, and control aphids and other sucking insects that spread viral diseases. Dark, yellow-bordered spots are leaf blight caused by fungi. Spray with fish emulsion or with sulfur ii disease is severe. Carrot weevils eat roots and make leaves yellow for controls, see Roots with dark tun--nels on page 61. See the Herbs entry beginning on page 116 for other possible problems. 

Leaves with dark, velvety patches. Cause Pear scab. The spots are mostly on leaf undersides, and infected leaves often pucker and drop. For more information, see Fruit with olive-brown, corky spots that turn dark brow n" on page 168. 

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