Diseases and pests of cucurbits
Viral diseases are very common in cucurbits, especially yellow cucumber mosaic, striking all vegetables of this group. There are mosaic on the leaves and fruits, yellow or light green spots. Infested plants grow worse, they bloom less and give a lower yield of low value. Viruses are transmitted by aphids. These diseases are prevented in the same way as with tomato viros.
In recent years, the dangerous disease of cucumbers has been spreading more and more in Poland, called angular bacterial spot of cucumbers. The most common symptoms of the disease are on the leaves. Yellow-green forms on them, "fat”, angular spots between the nerves. The tissues within the spots die quickly, turn brown and flake off, as a result, holes are formed in the leaves. Similar spots are formed on the petioles, fruit, and also on the cotyledons of seedlings. Heavily infested fruits are distorted and rot easily. This disease is prevented by destroying plant debris after harvesting the fruit, making several-year breaks in cultivation and spraying cucumbers from the first symptoms of disease with Miedzian 50 in concentration 0,4%; repeat this treatment as needed 2-3 times, co 10-14 days.
At high humidity and high temperature, cucumber brown spots may appear on cucumbers and melons, the so-called. respect maniowatych. Dark ones develop on the surface of the fruit, recessed spots, velvety lapping, olive-black coating. Sometimes drops of mucus are released in these places. Infested fruits tend to be smaller, distorted and rot easily. This disease is controlled by spraying – in periods of rainy weather co 7-10 days after the appearance of leaf disease, fruit buds and fruits – preparations: funaben 50 in concentration 0,07%, Dithane M-45 – 0,2% or Topsinem M – 0,07%.
Melons, and, to a lesser extent, pumpkins, are affected by gangrenous blotch, also called cucurbits anthracnose. This disease is especially dangerous in wet years. On the leaves, the stems, petioles, the root collar and fruit become yellowish, browning slightly recessed spots, transforming into wounds over time. Plants wilt, they die; the fruit stops growing, turn bitter and rot. This disease is controlled in a similar way to the scab of cucurbits.
Cucumbers and pumpkins, both under glass, as well as in the ground, it attacks powdery mildew, which simultaneously attacks many other plant species. On the leaves of infected plants, and sometimes also at the tops of the shoots, there are spots of a mealy coating, as a result, leaves die prematurely, which in turn has a negative effect on the fruit yield. The fungus that causes the disease, hibernates on the remains of infected cucumbers, left after harvest, and on perennials of other species. The disease is treated as soon as its symptoms develop by spraying the plants 2-3 times, co 7-10 days, preparations: funaben 50 in concentration 0,07%, Morestan – 0,05%, Extra sulfur – 0,4% lub Topsin M – 0,07%.
The more common pests on cucurbits should be replaced: spider mite, cream, sprout and aphids.
The spider mite is a typical polyphage, attacking not only cucurbits, but beans, hop (hence its name), many ornamental plants and some fruit trees. Both adult forms are harmful (female, length 0,4 mm, has a yellow-green color, with two gray spots; the wintering form is carmine in color; male, length 0,3 mm, it is yellowish), and the larvae. The underside of the leaf of a plant attacked by this pest is covered with a faintly visible yarn, under which they lay their eggs and feed, sucking tiny juices, spherical spider mites, also called "red spider"”. Sick leaves turn white and wither. The spider mite reproduces very quickly, when it's warm and dry, and in our climate it gives 4-5 generations throughout the year. When this pest appears on a mass scale, the plants are sprayed with preparations: Mite extra liquid 8 in concentration 0,1%, Liquid sadophos 30 – 0,4%, Torque 50 WP – 0,05% or liquid vinylphos 50 – 0,1%.
The sprout cream is similar to our housefly, but smaller. Her larvae, they strongly damage germinating seeds and cucumber seedlings, destroying the crops. To prevent this pest from occurring, seeds must be dry dressed with Nexion L mixed mortar.