Kazakh National Agrarian University
The Departament: Plant protection and quarantine
Independent work of student
Theme: The main pests of cotton diseases and protective measures
Prepared by : Kuttybai Akerke
Croup by:
Checked by: Makhanova Gulnur
Almaty 2017
The contents
Introduction
The main part
Disease of rye and protective measures
Pests of rye and protective measures
Conclusion
Literature
Introduction
Cotton (Latin Gossypium) is a genus of the Malvaceae family, including more than 50 species of arboreal and herbaceous, perennial, biennial and annual plants originating in the tropical and subtropical regions of Asia, America, Africa and Australia. Cultural forms on an industrial scale are grown throughout the world as spinning plants. It is a source of vegetable fibers for the textile industry - cotton.
Species of the genus Cotton - one- or two-year-old herbaceous plants up to 1-2 m high with very branchy stems. The root system is rooted, the root goes to the ground to a depth of 30 cm, and in some varieties it reaches three meters.
Leaves alternate, with long petioles, usually 3-5-lobed.
Flowers are single, numerous, different in color. The flower consists of a corolla with three to five broad and intergrowth petals and a double five-toothed green calyx surrounded by a three-bladed wrapper that is many times longer than the calyx. Numerous stamens coalesce into the tube. The flower formula is: * K 3 + (5) C 5 A (∞) G (5 _) {\ displaystyle \ ast K_ {3+ (5)} \; C_ {5} \; A _ {(\ infty)} \ ; G _ {({\ underline {5}})}}
Fruit is a capsule, sometimes more round, in other cases oval, 3-5-split, cracking along the valves, with numerous dark brown seeds inside it, covered on the surface with soft sinuous hairs-cotton. Two types of cotton hairs are divided. They can be long and fluffy or short and fleecy - the so-called lint, cotton fluff. On the seed, depending on the variety and growing conditions, there can be both both types of hairs, and only long ones. Wild species of long hairs do not. The cotton seed, covered with a dense skin, contains an embryo consisting of a root and two seminal lobes.
II. The main part
Disease of rye and protective measures
During the summer, and in particular, shortly before the onset of ripening of cotton, various diseases usually appear. In the diseases of these, there are mainly two reasons: physiological, resulting from malnutrition of plants, or diseases caused by fungi and bacteria.
Falling leaves, caused by fungi of the genus Alternaria (Alternaria): Alternaria macrospora and Alternaria alternata.
Anthracnose of cotton, caused by a fungus of the species Colletotrichum gossypii.
Brown rot, causative agent - fungus Thielaviopsis basicola.
Gummosis, caused by bacteria Xanthomonas campestris pv. malvacearum.
Fusarium rot of the capsules, caused by fungi of the genus Fusarium.
Phytophthora, called Phytophthora nicotianae var. parasitica.
White rot, caused by the fungus Sclerotinia sclerotiorum.
1. Wilt
Wilt is a widespread malignant disease of cotton.
Cotton is affected by agents of the verticillium and Fusarium wilt.
1.1. Verticillium wilt.
The causative agent of the disease is the soil multifilar fungus Verticillium dahliae.
The loss of cotton crop from the unit area depends on the number of diseased plants on the field, the intensity of the disease and the timing of the manifestation of the disease. The earlier and more intensively the wilt appears, the greater the loss of harvest. When Wilt is affected by 26.4% of cotton plantations in early development (in late June and early July), losses harvest, i.e. the reduction in the number of bolls is 90.5%; at late appearance (at the end of August and early September) when the wilt affected by wilt was 88.8%, the losses were 29.7%, respectively.
On sick plants the quantity of a crop and its quality decreases - the length, a fortress and breaking length of a fiber decreases, the quality of seeds also worsens - they become puny, with the lowered germination, energy of germination. Technical seeds have a low percentage of fat.
1.2. Fusarium Wilt
Fusarium wilt is a disease of fine-fiber varieties of cotton. Pathogen is Fusarium oxysporum f. Vasinfectum Bilai, it penetrates plants through the roots.
Fusarium wilt infects cotton from the seedling phase until the end of vegetation. The degree of development of the disease depends on the stability of the planted variety, the weather conditions of the year, the level of crop culture, timely and high-quality implementation of anti-roll measures. On cotton seedlings of G. species in carbadense, the disease manifests itself on cotyledonous leaves in the form of yellowish mesh in one corner of the leaf. With the growth of the lesion, the mesh increases until it covers the entire surface of the leaf. The mesh, which appears on the leaf blades, is an irregular yellowish fringe.
Plants, the disease in the phase of five to seven real leaves, have shortened internodes, which is why they lag behind in growth and development.
Measures to combat cotton wilt
a) In order to accelerate the elimination of hot spots of cotton in wilts (70% or more) and maintain high resistance of new varieties in farms, it is necessary to use cotton-crop rotations with a more frequent alternation of crops according to the 1: 2 scheme, which strengthen soil cleansing from infection and prevent virulence of the pathogen.
b) To enrich the soil with organic matter and change the soil microbiocenosis to the side unfavorable for the development of the parasitic fungus, after harvesting maize, vegetables, melons and other crops, plant repeated and intermediate siderial crops. You can use rye, barley, mustard, rapeseed, peas, vetch and others. When re-seeding the precursors, the green mass is smothered in autumn under autumn plowing or in spring plowing.
d) Sprinkling of cotton with a 1.5% carbamide solution in the phase of two to five leaves at a rate of 400 l / ha of working fluid.
e) To prevent the harmful effects of hornfels and fosalons on cotton grown on the fields infected with the wilt pathogen, carbamide is added to the working solution of these insecticides.
Gummosis - bacterial disease of cotton
The causative agent of gommas is the parasitic bacterium Xanthomonas malvaccarum Dow. The most favorable temperature for its development and infection of plants is + 25, + 28 ° C. At temperatures below 25 ° and above 35 °, the viability of bacteria decreases.
The development of this disease is associated with weather conditions. In areas where there is a lot of precipitation in the spring and in the first half of summer, cotton is especially exposed to gummosis. All overground parts of plants are ill: cotyledons, leaves, stems, boxes and fiber. When the disease of the plant is reduced, not only the yield of raw cotton, but also the seed quality of the seeds and the technological qualities of the fiber. If the cotyledons and real leaves are greatly affected, the yield of raw cotton is reduced by 4 to 9%, and in the case of stem damage by 18 to 62%. Often, in stalk gommosis, cotton does not yield crops at all.
On the cotyledons the disease manifests itself in the form of dark green, oily translucent spots scattered across the leaf plate. Spots have a rounded shape. On the surface of gummy spots, a thick sticky liquid is released - a gum, which contains a lot of bacteria gommoza. Over time, the gum dries to form a greyish film. With severe damage, the disease passes to the petiole, and then to the stem and growth point. When affected by gummosis, the growth points of young plants usually die, and the crops become thinned.
Control measures
1. Carry out thorough preparation of the soil for sowing with planning of fields to avoid the accumulation of rain and irrigation water in low places.
2. Use for sowing well-ripened high-quality seeds.
3. When sowing cotton seeds, before sowing, they are treated with 80% TMTD at the rate of 8 kg / t or fentiuram at the rate of 12 kg / t. The delented seeds for precision sowing are pre-sorted, calibrated and treated with 80% TMTD at a rate of 19 kg / ton or fentiuram of 12 kg / ton.
4. Differentiated normal seeding, depending on the duration of sowing and soil moisture.
5. Timely loosening of the crust in rows after the rains and cultivation of row spacing.
Black root rot
Black root rot affects the shoots and adult plants of Soviet fine-grained cotton and shoots of medium-fiber cotton. The causative agent of this disease is the soil fungus Thielaviopsis basicola Ferr., Which, in addition to cotton, affects a number of other crops. It is not affected by this mushroom, alfalfa, cereal grains, corn, sorghum. In soil, the fungus persists for many years, feeding on the products of the decomposition of organic substances.
In crops, the disease appears five to six days after emergence with a gradual increase within 15 to 20 days. As the soil temperature rises, the disease recedes. In autumn (in September) there is a disease of adult plants, which lasts until the end of vegetation.
The germination of sprouts is favored by cold rainy weather, delaying their appearance and development. In some years, up to 30% of the shoots fall from the black root rot, which leads to a thinning of the crops. The autumnal appearance of the disease contributes to excessive soil moisture.
On shoots the disease manifests itself in the withering of cotyledons, lodging and death. In the case of dead plants, the tissues of the root system become yellow-brown and have fungal spores.
Measures to combat black root rot are the same as those with root rot. Against the autumn disease it is recommended not to produce heavy watering, leading to waterlogging of the soil.