Actuality and importance of the topic of dissertation. Cotton is cultivated in territories of more than 80 countries of the world and has an essential value in economy of the USA, India, China, Brazil, Pakistan, Egypt, Uzbekistan and other countries. During the evolution about 1500 kinds of animals’ arthropods have adapted to cotton. The general losses of cotton crop due to arthropods’ damages arc more than 19 %.
Introduction of cotton growing method under a film let to notice changes in the development of harmful organisms (pests, diseases and weeds). In this case, it is necessary to study an interconnection of organisms in the new developed ecological conditions. In view of artificial creation of a microclimate under a film, the processes of shoots diseases by rot, gummosis etc can proceed on special ways. And consequently it is required to study these processes and to introduce corrective amendments into the system of plants protection. Value of agrorcccptions in cotton wilt development is great. And, hence, it is necessary to study and clear up the method at double decrease of cultivations and waterings quantity that has indispensable value for wilt development.
Developments of herbicidal protection of crops with reference to a method of cotton growing under a film arc necessary. Because of early occurrence of shoots, entomoccnosis is formed earlier on sites where the new method is used. And so, development of establishment of terms of occurrence and injuriousness of both harmful and useful kinds of entomoccnosis and methods to allow to keep and multiply useful entomoccnosis with smaller expenses and to reduce to a minimum the crop losses arc necessary.
In Uzbekistan two basic schemes of cotton plant cultivation with rowspacings of 60 and 90 cm arc accepted. Hence, it is required to state an entomo-logic and phytopathologic estimation of cotton crops with various placing of plants in row-spacings and density of crops.
In connection with the above-stated, there was a problem on entering of amendments into the existing integrated system of cotton protection at various ways and schemes of plants placing. This dissertation is directed on fulfillment of decrees of the law of the Republic of Uzbekistan “On protection of agricultural plants against pests, diseases and weeds” and also regulations of the Cabinet of Ministers of the Republic of Uzbekistan on March, 29, 2004 under #148 - “On improvement of plant protection service and ways of increasing their effectiveness”.
The purpose of the research. Improvement of integrated system of cotton protection sown by different methods (different chcmes and plants density of standing, introduction of a new method - “cotton - grain crops” and also method of cotton sowing under a film with consideration of possible bioccnological, phytopathological and hcrbological changes. For fulfillment of these goals the following tasks were put:
entomological, phytopathological and hcrbological estimation of a new chcmc of "cotton-grain crops" rotation on the base of changes to occure at their agrobiocenosis;
to study development of cutworms, cotton worm, aphids, thrips, spider mites and other insect pests and bcneficials on crops sown using various designs and plant density;
to establish a difference of infection with root rots, gummosis, wilt, and also diseases of bolls and fiber rots on crops with different designs and plant density;
to establish a difference in infection and infestation of under film parts of cotton seedlings (root rots, cutworms, weeds) of early seedlings obtained at the methof of cotton sowing under a film;
development of pests at over film parts, establishment of phenograms and injuriosness of kinds and also the ways of their control;
to study development at dynamics of useful insects and alteration of biological control structure on cotton crops sown by different methods;
improvement of means and methods of cotton seedlings’ diseases, pests and weeds control;
to study development at dynamics of useful insects and alteration of biological control structure on cotton crops sown by different methods;
improvement of means and methods of cotton seedlings’ diseases, pests and weeds control;
to establish sharp and remaining toxicity of effects of defoliation and defoliants used at early terms on mulched crops against harmful objects;
to make agrotoxilogical investigations for revealing the perspective insecticides and acaricides against main pests of cotton plant;
to estimate quality efficacy of raw cotton obtained at sowing by different ways;
to estimate both farm and economical efficacy of different ways of cotton sowing and its protection;
to carry in changes into the structure of existing system of plant protection at sowing by different designs and densities of plants standing.
Scientific novelty of work. For the first time both entomological and microbiological changes (from the point of phytopathology) occurring in agricultural biocoenosis of fields where the crop rotation “cotton-grain crops” is used for many years, were determined;
differences in infection I infestation of plants by diseases and pests were revealed on fields with various sowing schemes and plant density;
estimated effectiveness of Stomp herbicide (2,0 1/ha) for weed control at the methof of cotton sowing under a film;
it is established that cotton sowing under a plastic film leads to early appearing and early development of pests; in particular, cotton worms develop longer and give 3 generations for a season;
determined the positive estimation of defoliation carried out for 20-25 days earlier against common dates on harmful entomofauna, in particular, on aphids and cotton boll worms.
CONCLUSION
1. Absence of fall ploughing in conditions of wheat sown in autumn on the cotton field and next growing of intermediate (stubble) crops like com allows the pests of agricultural crops not only to overwinter safely, but also to increase their density. In particular, density of cutworms increases by 79,6%, aphids - by 9% and spider mites - by 25%; the flight of cotton bollworms’ butterflies increases by 45%, and number of their eggs and larvae increases by 2-3 times.
2. Density of entomophages on cotton fields grown after different previous crops has varied. So, density of coccincllids (7-spottcd ladybirds, stetorus) and s lacewings was higher on cotton fields included in “cotton-grain crops” rotation system; that of mitivorous thrips did not change. On plots with crop rotation the plants were more diseased by root rot (24,8-29,3%), by wilt (11,4-21,8%), but less by gummosis (15,4-8,8%).
3. The following results of plants infection by various pest organisms, and also of cotton productivity have been received.
3.1.On crops with 60 cm raw-spasings the plants arc more frequently infected than at 90 cm raw-spasings :with root rots (by 5,2-9,6%), gummosis (by 6-6,2%) and wilt (by 32-21%). By the autumn the numbers of infected bolls and fiber have also increased. Increase of plants density caused increase of infected plants with root rot (6,9-2,5%), but decrease of infected plants by gummosis (4,9-9,1%). The plants with 60 cm raw-spasings arc infected with wilt more frequently (5,6-11,8%), than at 90 cm ("Andijan-36" variety); at more densely sown cotton the number of plants infected by wilt decreases (by 11,6-6,9%). The numbers of infected bolls and fiber on plants with 60 cm row-spacings and also on dense sowings have increased as well.
3.2. On plants with 60 cm raw-spasings infestation with aphids was less(17,l-22,5%) and their density has decreased by 7-8% than at 90 cm raw-spacings.
Width of row-spacings has not affected development of thrips, but infestation has increased with increase of plants density. Numbers of spider mites were higher on plans with smaller raw-spacings (60 cm) and their density was higher by 31,7-149,8%. Development of cutworms did not differ on cotton crops with different sowing schemes and plant density, but their negative effects on yield have decreased with increase of plants density. Infestation of plants with cotton bollworms was more severe (78-48,5 %) and the density of its larvae was higher (14,7-27,7) on plants with with 60 cm row-spacings. With increase of plants density the number of larvae per 100 plants has decreased (in average by 8% in 60 cm and by 16,4% in 90 cm raw-spacings), but the number of populated plants has increased (16,0% at 60 cm and 37,5% in 90 cm raw-spacings). Therefore, on fields with density of plants more than 1,5 times, ET criterion is to be equal to 7-8 larvae of younger instars instead of 10-12 ones.
3.3. The microclimate created on a surface and around plants at different sowing schemes and plant density affects the diseases and development of plants. So, plants grown on 90 cm raw-spasings have increased dry weight by 9,2-11,6%, and the ratio of stalks to cotton was 1:0,29-0,39 and it raises with increase of plants density; thus the yield of each cotton boll was more by 0,2-0,3 g. The plants sown on wider row-spacings have produced higher yields by 9,8-10,1% (3,3-3,6 c/ha), and an increase in plants density led to increase of yield by 3,0-4,0 c/ha; the first harvest provided higher amount of raw-cotton by 9,6-8,9%. But at the same time, the quality of a fiber produced at very dense crops (157 - 159 thousand plants/ha) was the worst.
From the above-stated it is possible to conclude that the most optimum cotton sowing design on meadow-grey soils was 90x8-1 (with a real density 130 000 plants/ha) and row-spacing 90 cm. These treatments have provided with the highest economic efficacy and profitability. This scheme of sowing and plants standing density arc recommended into production.
4. Occurrence of weeds at different sowing methods did not differ. Futher development of weeds (in May-June) depends on on temperature and humidity of air. Up to 31-72% and 30,5-75% of weeds were killed under the transparent and black films respectively. As weather prediction is not available and/or not cnouph reliable, it is necessary to apply pre-sowing soil herbicides on crops with MCSUF. The experiments substantiated a possibility of pre-sowing use of herbicide Stomp (2 1/ha) for these purposes. This herbicide could protect a crop against annual weeds during 60 days after treatment with a biological efficacy equal to 96-97%. Efficacy of Cotoran (2,5 kg/ha) was lower (74,5-85,3-85,5%). The obtained positive results arc recommended into production.
5. Cotton plants grown under a film were infected less with root rot (30-38%) and gummosis (21-34%). Application of the MCSUF together with presowing seed treatment have provided higher efficacy against pest organisms than without a film and at other terms. Panoctinc has provided 59-65% efficacy against root rot and Bronotac - 80-71% efficacy against gummosis and they were recommended into production.
6. Cotton sown under a film has been infected with a wilt disease less than at control. The plants protected by film (on cuts of 20.09) were equal to 7,1 ±2,3% -6,0±3,4%, whereas at the standard (sowing in mid-April) - 14,1% -11,3%. The reason of this was less number of cultivations and irrigations at MCSUF, that reflects the positive side of the method.
7. The trophic relations of arthropod animals with cotton, sown under a film, have changed. That was expressed in the following:
7.1. Fast and early development of cotton seedlings sown under a film, provides partial escaping plants from infestation with cutworms. Damage of these pests can be reduced by 47-44%. Seedlings grown from seeds treated with Gaucho (Dalucho, Avalanche) - 5 kg/t, Orthcn - 4 kg/t, Rapcol - 10 kg/t and Cruiser - 4 kg/t can be protected against cutworms during 30-35 days with an efficacy equal to 66% - 82%.Thcse insecticides arc recommended to a wide application in manufacture.
7.2. Aphids and thrips start to develop earlier and they develop longer on early germinated cotton seedlings. Plants grown from treated (Gaucho, Orthcnc, Rapcol and Cruiser) seeds practically do not need insecticide sprayings. All preparats arc recommended into manufacture.
7.3. Early germinated cotton seedlings have started to be occupied by the spider mites and their predators early. But then, the difference between cotton sown under a film and in common terms is getting insignificant. The numbers of acariphags of natural populations increases since April and reaches its satisfactory maximum by the 2-3 decades of August. But, chemical processing is necessary before it. The recommendations arc included into the common scheme of protection.
7.4. Mirid bugs appear on cotton grown at MCSUF earlier than usual, and complete their development together with plants. These bugs control is included into the general system of control.
7.5. Cotton bollworms start to occupy early grown cotton plants (in I decade of June) when it can give 3,5 generations, and it produces 3 generations on plants grown by common practice. This has required modifying the system and terms of control against this pest. In particular, it is necessary to start application of the biological method on such fields earlier basing on results of the feromon monitorings. Early maturing of cotton and shift in agricultural methods, including terms of defoliation, breaks the historically developed terms of bollworms’ preparation to overwinter and can negatively affect an annual cycle of insect’s degradation. All that is a positive characteristic for a method of cotton growing under a film.
8. Because of early maturing of plants and earlier terms of defoliation MCSUF ensures the reduction of density of cotton bollworms both in current and the next year. Defoliants to have insecticide effects arc next: Dropp ultra (0,4-0,6 1/ha), Avguron extra (0,07-0,15 1/ha), Magnesium chlorate (7-10 kg/ha), Sihat (10-13 kg/ha) and Harway (2,0 kg/ha). The early defoliation allows to yield cotton at early terms, to prepare the soil and to sow grain crops with seeders and to obtain more productive plants.
9. The beginning and completion of raw-cotton harvest from plants, sown by MCSUF occures early (at I-II decades of October). Plants sown on March, 15-20 at MCSUF can produce an additional yield at rate of 11,3 -18,4 kg/ha. Cotton sowing under a plastic film on terms later than optimum (III decade of April) did not provide with necessary farm and economic efficacy.
10. Treatment of cotton seeds with pesticides Bronotac, Panoctine, Gaucho (Dalucho, Avalanche), Orthcne, Rapcol and Cruiser at sowing under a film provides obtaining of additional crop in amounts of 3,7-5,0 c/ha (1998) or 3,3-4,8 c/ha (1999 and 2007). The quality parameters of cotton-fiber from experimental sites have been improved than those produced at use of common sowing method.
11. The experiments of 1999 provided with additional cotton yield of C-6524 variety sown under a film in amounts of 11,3 c/ha (profitability was 39,3%). At industrial experiment of 2008, (“Andijan-36” variety) an additional yield in amount of 8,5 c/ha has been obtained. Profitability of expenses was 37,9%. That is by 13,7% higher than at controLThus, the method of cotton sowing under a film allows receiving considerable rise of a crop and a quality of cotton. On the other hand, early terms of harvesting and clearing of sites positively affects not only the crops of subsequent winter wheat, but also improves the structure of agrobioccnosis of the given sites.