In order to manage pests judiciously, it is necessary to know the reasons why certain insects are considered harmful and the factors that lead to this situation. This applies to the microbiological method just as much as to any other method of struggle. Accordingly, to set general principles that need to be taken into account when striving for best use microbiological methods should analyze the origin of pests and the results of the use of non-microbiological methods of combating them. For our purposes, a pest should be considered any type of insect, tick (or representative of another group of animals) that causes economic harm, creates inconvenience to humans or threatens human health.
The number of insects before the advent of farmers
Based modern knowledge it can be assumed that before human intervention, the abundance of any insect species depended on a balance between its ability to reproduce and a combination of various natural factors that more or less limited its abundance. These factors include climate, weather, size of resources available for use, competitors, natural enemies and pathogens.
Many rapidly reproducing species fed on plants and themselves formed the animal basis of food chains. Many species were, of course, naturally abundant, and some of them no doubt caused as much damage as some modern pests, such as pests of virgin coniferous forests. Some species reproduced so intensively that they temporarily destroyed their food sources, as sometimes happens in our time with pine moths, Bupalus piniarius, in the pine forests of Europe. The number of many species fluctuated from year to year, depending on weather conditions years and food supplies. Food chains have never been static: in some species, a periodic change in perennial cycles of high and low abundance was observed. There were, of course, even longer cycles, lasting millions of years, driven by strong climate change and evolution.
Many species never reached high numbers as a result of interaction with a complex of natural enemies acting under the overlapping influence of climate. All such interactions are extremely complex and depend on many additional factors, including weather, habitat conditions and fauna composition.
The forces limiting the number of insect species were a complex of abiotic and biotic factors acting at various levels of population size. The cumulative influence of factors caused natural death. Since, at the end of a certain seasonal cycle, the number of insects increases only if more than two individuals survive and reproduce from the offspring of one female, it is likely that the overall increase or decrease in the number of a species often depends on relatively small changes in mortality. So, if (to take a simple example of a species that gives one generation a year, the females of which lay 100 eggs, then in order to maintain a constant population level, 98% of the offspring must die without breeding. A change in mortality by 0.5% can increase or decrease by 25 % pest population next year.
Farmer intervention
Chemical pest control
In connection with the widespread use of pesticides, a number of rules have been developed that the entomologist must reckon with when applying the microbiological method. Failure to comply with these and the following rules has already caused a number of failures.
1. The pesticide must actively act on the pest scheduled for destruction.
2. It should not have a phytotoxic effect.
3. The lethal dose should affect the pest in the form of a preparation of the most appropriate composition.
4. The drug should be used during the vulnerable stage of the pest and within the time limits preventing economic damage to the crop.
5. It is necessary to monitor the development of pest resistance to pesticides,
6. The harm of pesticides to natural enemies should be minimized.
7. Chemicals to be used should be selected that are safe for control workers and wildlife. Do not allow dangerous residues of poison to remain on plants and in the soil.
8. Pesticides must be stable during storage prior to use.
The current interest in biological control is largely due to the development of pesticide resistance in pests. The increasing cost of developing new pesticides, driven in no small part by the need for sophisticated test methods to ensure that there are no undesirable side effects residues requires pesticides to be suitable for use over large areas of critical crops. These limitations place a heavy burden on high-intensity cropping systems, so it is critical to extend the timeframe for the cost-effective use of existing products.
biological method control is a promising alternative to chemical, but effective natural agents are known only for a few species from the entire pest complex. This limitation paved the way for integrated systems, bringing together all available ways the fight against the whole complex of pests as a whole. One of the main obstacles to the development of integrated control programs is the lack of selective pesticides and the problem of the selective use of broad-spectrum pesticides. The limited host range of many pathogens allows us to hope that they will be suitable for use in integrated programs.
Biological methods of pest control
Task 1. Fill in the table.
Features of the development of insect pests.
View Group Wintering stage of development Wintering place Feeding the larva cabbage white Lepidoptera chrysalis trees and soil ground parts of plants beet weevil Coleoptera chrysalis the soil plant roots Colorado beetle Coleoptera chrysalis the soil plant roots codling moth Lepidoptera caterpillar in a cocoon fruit storage plants, apples, quince apple flower beetle Coleoptera caterpillar in a cocoon fallen leaves bud juice, apple buds Chafer Coleoptera chrysalis the soil roots of trees, plants gypsy moth Lepidoptera egg bark depressions leaves Pine silkworm Lepidoptera egg trunks and stumps plant sap
Task 2. Ten Colorado beetles eat 2000 sq. cm of potato leaves for 30 days. During the period of its development, the larva of the Colorado potato beetle eats about 50 sq. cm of potato leaves. Calculate and write down the area of potato leaves that 1,000 Colorado potato beetles will eat. How many larvae of this beetle can destroy the same area of leaves? Based on the above calculations, draw a conclusion about the effect of the Colorado potato beetle on the yield of potatoes.
10 beetles = 2000 sq.cm
1000 zhov - x sq.cm
x \u003d 1000 * 2000/10 \u003d 20,000 sq. cm - the area that 20,000/50 \u003d 400 larvae will eat.
Task 3. Complete the scheme.
Pest reduction methods:
1. Chemical: spraying with pesticides, poison baits, treatment with bleach, treatment of plants with poison.
2. Physical: collecting pests, catching with special devices, killing mosquito larvae with kerosene.
3. Agrotechnical: sowing and planting of plants is carried out in such a way that they have time to get stronger by the time pests appear.
Task 4. Fill in the table.
Insects - carriers of pathogens.
Task 5. The housefly breeds very quickly. For example, one fly lays approximately 120 eggs at a time. During the summer, seven generations of flies can appear, about half of which are females. Calculate and write down why it doesn't actually happen.
We will take April 15 as the beginning of the first clutch and we will assume that the female fly will grow so much in 20 days that she herself will be able to lay eggs. Then reproduction will take place as follows: April 15 - the female lays 120 eggs; in early May, 120 flies grew up, of which 60 were females; May 5 - each female lays 120 eggs; in mid-May, 120*60=7200 flies come out, of which 3500 are females, and so on.
In fact, this does not happen, because many individuals die as a result of natural selection.
Objectives: To introduce students to appearance especially dangerous insect pests of the garden and forest, talk about their harm and measures to reduce the number.
Equipment: table "Insects - pests of the garden and forest"; separate drawings of insect development for mounting on a wall board; collection material.
Methods and methodological techniques: teacher's story with elements of conversation using visual visual aids, independent work students with a textbook.
During the classes
It is advisable to start the lesson with a compacted test of students' knowledge: oral individual about insect pests of the field and garden and written individual (according to didactic cards) about arthropods.
Questions for oral knowledge testing:
1. What harm do locusts and bears bring?
2. Why are aphids and bug-harmful turtles dangerous and for which cultivated plants?
3. What harm do beet weevil and Colorado potato beetle cause in fields and vegetable gardens?
4. What kind of damage to fields and gardens is caused by the cabbage butterfly and the winter scoop butterfly?
For a written test of knowledge, you can use the cards that were offered in previous lessons. After clarifying and concretizing the answers of the students, the teacher shows images of garden pests and invites students to say what these insects are called, which ones they saw alive, what harm each of them causes to a person. Students are unlikely to be able to give complete answers, so the teacher himself says that often during the flowering of apple trees, many buds do not bloom, the flowers turn brown, and if you open such a bud, then it contains a larva or pupa of an apple flower beetle. It draws attention to the fact that many of the formed apples fall off prematurely, each of them has a wormhole, and in a cut apple you can see the caterpillar of the codling moth butterfly.
After the teacher tells that during the flowering of strawberries, many of its peduncles are drooping, as if cut, the ripening fruits of raspberries and currants are “wormy”; shows images of affected plants and insects associated with such lesions.
Noting that aphids and many other insects cause great harm in the gardens, the teacher shows an image of a gypsy moth and tells why this butterfly is so named, why it is dangerous, at what stage it hibernates, by what signs its oviposition can be recognized.
Of the other dangerous pests of the forest, the teacher introduces students to the pine silkworm butterfly, bark beetles, barbel beetles, talks about the harm caused to forests by the May beetle.
Informing that about 700 species of insect pests damage agriculture and forestry in our country, the teacher names mechanical, agrotechnical, chemical and biological methods of dealing with them. Invites students to tell which of these methods help reduce the number of insects they already know: locust, harmful turtle, apple beetle, raspberry beetle, gooseberry moth, gypsy moth, etc.
After clarifying and supplementing the answers of students, the teacher asks the question: what pest control methods are most effective and why?
After the teacher gives a homework assignment: read the text of the paragraph in the textbook and answer the questions; fill in the table “Insects - pests of the garden and forest” in the notebook (name of insect pests, their belonging to the detachment, causing harm), reveal the content of the concepts: “methods for reducing the number of insect pests” (mechanical, agrotechnical, chemical, biological).
Of the beetles, the Colorado potato beetle, beet weevil, and click beetle are widespread in fields and gardens. The Colorado potato beetle is a dangerous potato pest. During the summer, 2-3 generations of beetles develop. Adult beetles and their larvae feed on potato leaves. Beet weevil brings the greatest harm during the period of beet growth. At this time, worm-like larvae hatch from the eggs laid by the females, feeding on its roots. Click beetles damage many crops. Their worm-like elastic larvae - wireworms - bite into potato tubers, root crops of carrots, beets, and plant roots.
Of the Lepidoptera in the fields and gardens, white butterflies (cabbage, turnip, rutabaga) and winter scoop bring great harm. Caterpillars of white butterflies feed on the leaves of cabbage and other cruciferous plants, leaving only large veins. Caterpillars of the winter scoop live in the soil, where they destroy the sown seeds and emerging seedlings, gnaw through the stems of plants at the soil level, and crawling to the surface, eat the leaves (they feed on more than 140 species of plants).
Of the Diptera, some flies harm field and garden plants. females onion fly, for example, lay their eggs on lumps of soil near onions or garlic. The hatched legless larvae bore into the bulbs and green leaves, eat out their passages. Damaged plants turn yellow and dry out. Similar harm is caused by cabbage and carrot flies, the larvae of which feed on the roots of cruciferous plants.
Insects - pests garden. On the plants of the garden, the most common are aphids, apple flower beetle, strawberry weevil, raspberry beetle. The larvae of the apple flower beetle develop in the unblown flowers of apple trees, eating out the ovaries and stamens, the larvae of the strawberry weevil - in the unblown flowers of strawberries, strawberries and raspberries, the larvae of the raspberry beetle - in raspberry flowers. Butterflies do great harm in gardens - the codling moth (caterpillars develop in the resulting apples) and gooseberry moth (caterpillars live in gooseberries and currants).
Insects- forest pests. The most dangerous forest pest is the gypsy moth. The caterpillars of this butterfly feed on the leaves of many trees. During the years of mass reproduction of the pest, the trees of the forest (and garden) can completely lose their leaves. May beetles feed on the leaves of oak, birch, maple, and their larvae, which develop in the soil, gnaw on the roots of young trees. In coniferous forests, pine silkworm causes significant harm. The caterpillars of this butterfly damage mainly pine, less often spruce and larch. Bark beetles settle in the bark of weakened trees.
Measures to reduce the number of insect pests. On the territory of our country there are about 700 species of insects - dangerous pests of agriculture and forestry. To reduce their numbers, they use various ways: mechanical (crushing eggs of cabbage butterflies, destruction of beet weevils in trapping grooves, etc.), agrotechnical (sowing or planting plants in such a way that they have time to get stronger and become tough for the appearance of pests, cleaning the bark on the trunks fruit trees, regular collection of fallen fruits, etc.). In the case of mass reproduction of pests, chemical methods: pollination and spraying of plants with toxic substances (at the same time, unfortunately, many insects, earthworms, birds die). Nowadays great importance acquire biological methods of plant protection: the protection and attraction of insectivorous birds, bats, the use of biological preparations that cause diseases of insect pests, as well as the breeding and use of other insects - natural enemies of insects that harm plants. In the latter case, some predatory insects, egg-eaters and riders.
Predatory insects. Many types of insect predators are of great help in curbing the number of insect pests of plants. Predatory beetles ladybugs(seven-spot, two-spot, etc.) eat aphids, ground beetles - various caterpillars. The larvae of these insects are also predators. Red forest ants protect the forest from various pests.
Insects are carriers of human pathogens. Some insects, especially blood-sucking ones, are carriers of pathogens of dangerous human and animal diseases. house flies, flying into a person’s housing, are transferred on their paws from sewage to food (available for their visit) pathogens typhoid fever, dysentery, cholera and others dangerous diseases, roundworm eggs.
Malarial mosquitoes carry malaria pathogens. They can be distinguished from other mosquitoes by their landing: an ordinary mosquito holds its body parallel to the surface on which it sits, and a malarial mosquito - at an angle. The larvae of the malarial mosquito, having risen to the surface of the water, keep the body parallel to the surface film, and the larvae of the common mosquito - at an angle to it. The number of mosquitoes is reduced by draining swamps, breeding fish that eat mosquito larvae and pupae. Of great importance are their natural enemies - insectivorous birds (swallows, swifts) and dragonflies.
domesticated insects
Types of domestic insects. Of all the known insects, man has domesticated only honey bee and silkworm. When breeding bees, one could have honey and wax, and when breeding silkworms, one could have silk.
Measures to reduce the number of insect pests.
On the territory of our country there are about 700 species of insects - dangerous pests of agriculture and forestry. To reduce their numbers, various methods are used: mechanical (crushing eggs of cabbage butterflies, destroying beet weevils in trapping grooves, etc.), agrotechnical (sowing or planting plants in such a way that they have time to get stronger and become tough to the appearance of pests, cleaning the bark on the trunks of fruit trees, regular collection of fallen fruits, etc.). In the mass reproduction of pests, chemical methods are used: pollination and spraying of plants with toxic substances (at the same time, unfortunately, many insects, earthworms, and birds die). In our time, biological methods of plant protection are of great importance: the protection and attraction of insectivorous birds, bats, the use of biological preparations that cause diseases of insect pests, as well as the breeding and use of other insects - natural enemies of insects that harm plants. In the latter case, some predatory insects, egg-eaters and riders are used.
Predatory insects.
Many types of insect predators are of great help in curbing the number of insect pests of plants. Predatory ladybug beetles (seven-spotted, two-spotted, etc.) eat aphids, ground beetles - various caterpillars. The larvae of these insects are also predators. Red forest ants protect the forest from various pests.
Riders and egg-eaters.
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