![]() Bacteria proliferate in warm, moist weather and are spread from plant to plant by water, commonly in the form of splashing rain or runoff, as well as by insects or workers moving through the field. Affected plants will grow poorly, produce less fruit, and affected fruit is unmarketable.Īs with other bacterial diseases, outbreaks of angular leaf spot are often initiated from infected seed. ![]() These spots cause internal decay of fruit, and fruit that is infected early may be deformed. Spots can also appear on fruit, where they are tiny and water-soaked but dry to form whitish, chalky, spots. Similarly, water-soaked spots may appear on stems and petioles, drying out to form a whitish crust. Yellowing of the leaf between lesions may occur where disease severity is high. These wetlooking spots will dry out and turn yellow-brown or the dead tissue may fall out leaving a “shot-hole” appearance. Under moist conditions a milky white exudate containing bacterial cells may ooze out of the lesion on the lower leaf surface. Small, round water-soaked spots appear on leaf tissue, and expand until they are confined by veins, giving them the characteristic angular look. It will start to appear in the early to mid-season. This disease is usually among the first to show up because it is seed-borne. It is caused by the bacterium Pseudomonas syringae pv. lachrymans)Īngular leaf spot can affect all cucurbits, but cucumbers are most commonly affected. Angular leaf spot ( Psuedomonas syringae pv. Of course a diagnosis from a trained pathologist in the lab is ideal, but we understand it is not always possible to test every spot you encounter. ![]() Below are descriptions of some the more common fungal and bacterial leaf spots found on cucurbit crops in MA that we hope will help you tease them apart in the field. If an entire planting is infected, also dispose of any unused seeds, because it is possible that the seeds were infected with the virus.There are several diseases that cause leaf spots on these crops and they can often be hard to tell apart. To keep aphids from spreading CMV to other plants in your garden, pull up infected spinach plants and compost them. ![]() If viral diseases are common in your garden, use row covers (garden fleece) to protect young spinach plants from aphids. Grow plenty of nectar-producing flowers to attract aphid predators including ladybeetles, lacewings and hover flies. Measures that reduce aphid populations will cut the risk of CMV and other viral diseases in the garden. Preventing Problems:Ĭhoose resistant varieties, which are widely available. Yellow patches turn to brown as the disease advances. Leaves that are distorted by the virus cannot function normally, so plants struggle to grow and stop gaining size. Like other plant viruses, cucumber mosaic virus interferes with genetic signaling within the plant. When mature spinach plants are infected, mottled patches of yellow and green develop on older leaves, and new leaves close to the center may be small, yellow and twisted. On young plants, CMV causes leaves to become twisted and partially folded, and grow slowly. Mostly in warm temperate climates, where CMV is transmitted by aphids. On Crops: Spinach, lettuce, cucumbers, peas, and many flowers and weeds Where Found:
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