Physical control refers to managing pests by techniques including through barriers (such as screens or row coverings), hand-pulling weeds, and capturing, or removing the pest. Physical controls also include electrocution (rat zappers) and thermal controls (heat and cold therapy).
These are techniques that physically prevent pest insects from getting to their hosts. Some examples of barriers include floating row coverings for many horticultural crops, plant collars to prevent cutworms from attacking plants like tomatoes, and window screens to keep plant pests and health-harming insects out of greenhouses and buildings. Cockroach traps in houses are one kind of trap that may be used for control. Apple trees can have cardboard bands put around them that capture codling moth larvae; the bands are then taken off and disposed of. It is possible to lure certain pests—like earwigs and slugs—to their demise using beer-filled submerged traps.
A typical physical barrier we employ to keep pests out of our houses is window screening. Furthermore, pests can be physically eradicated from plants. For instance, misting the plant with water can help remove certain aphids and mites from the leaf. During the winter, bagworm eggs that are hibernating inside the bags can be taken out of the plants and killed. Certain pests can be captured with traps, and plants can be shielded from disease-causing insects or pests with barriers. Applying a band of folded hessian around the tree trunk to create an artificial resting place for the caterpillars and subsequently destroying them is an efficient way to manage gypsy moth larvae on small trees.
Many insects utilize pheromones to find partners, alert other insects to danger, identify food routes, and draw other insects to a particular location. In IPM programs, these alluring materials have shown to be quite helpful as instruments for monitoring and sampling, as well as for preventing pests from reproducing or eliminating them under specific circumstances. Certain kinds of insects also find particular colors to be highly appealing. For instance, sticky surfaced traps and yellow have been used to monitor a range of insect infestations.
Physical control involves the use of hands-on or mechanical methods to actively target and eradicate the pest. Weed control usually involves the use of physical measures. Weeds can be eliminated and their reproduction stopped via tillage, fire, manual removal, grazing, and mowing. Tillage can also harm some insects by destroying their eggs or overwintering stages of development. One operation is insufficient to manage weeds.
Combining techniques like summer fallow, post-harvest tillage, post-seeding tillage, and seedbed preparation can effectively suppress perennial weeds and their seedlings. The options will change depending on the crop, geography, level of infestation, soil quality, and equipment availability.
The choice of machinery is influenced by soil variables. For instance, mowing may be impeded by stones, and recurrent tillage may be avoided by moisture conservation. Take everything into account before creating an integrated control program.
Read: Options for Controlling Insect Pest Populations in Field Conditions
Harvest Practices
Strip harvesting keeps a strip of unharvested crops in the field, protecting it from mass insect migration, preserving natural opponents of pests, and enhancing snow management. Insects like beet webworms, pea aphids, cutworms, and grasshoppers may be forced to relocate if a whole field of afflicted crops is harvested. The harvest frequently removes beneficial insects, their home, and their food source if the crop contains them, which it most likely would if it is contaminated. With the harvest of the crop, the following generation of parasites may potentially be eliminated from the land. As a result, the insect frequently switches to a crop that is unaffected by its natural enemies. Strip harvesting contributes to the upkeep of a balanced ecology.
Sometimes a crop can be saved by swathing it early. Sawfly-infested wheat may have collapsed by the time it reaches maturity, making harvesting unfeasible. Sickly fields can be protected against weeds and pests like wheat stem sawflies by harvesting them early or turning them into silage or hay.
Grain mixtures should ideally be straight unless there is a suspicion of disease or insect presence, or unless rapid drying is necessary. Straight mixing enhances snow management and allows for longer stubble. Harvest timing may have an impact on production and the development of diseases. In late spring, pods are attacked by Alternaria black spot, which affects mustard and canola. Shattering losses from infected crops might be minimized by swathing them early. To promote drying, lay swaths so that air can flow beneath the grain. Sclerotritinia white mold can grow over the swath if the canola is wet.
Cereal crop grains that have overwintered in the swath, especially when covered in snow, may get contaminated with fungus that, under some situations, can create mycotoxins. Poisonous substances called mycotoxins are produced naturally as byproducts of fungi like Aspergillus, Fusarium, and Cephaolosporium. Vomitoxin, which Fusarium may make, causes sickness in people and loss of productivity in animals. It can be found in grain and hay. Ochratoxins are a class of mycotoxins that may cause cancer. They are present in tiny levels in grains that heat up while being stored on prairie farms. The flesh of pigs and poultry that have eaten tainted feed occasionally contains these mycotoxins.
Mowing and Hand-pulling
Regular mowing reduces the root stores of perennial weeds. Additionally, it will stop weeds that are annual or biennial from producing seeds. When plants are in buds, perennial weeds have the lowest root stores. This is the time if there will just be one mowing scheduled. Field bindweed and other prostrate weeds are not successfully removed by mowing. Agricultural insect pests’ helpful enemies are frequently harmed by mowing. To modify their mowing techniques, farmers must be aware of the life cycle and habitat requirements of the beneficial species. The provision of habitat for birds is a clear example. Many birds nest in the grass, and they eat enormous amounts of insects. One reason for the death of nestlings is early mowing.
Hand pulling works best for annual and biennial weeds, while tiny areas of persistent weeds can be pulled up frequently. Eliminating annual weeds stops seeds from being produced. If weeds are in blossom, stop the distribution of seeds by bagging and burning them. When attempting to stop the emergence of new species, hand pulling is most practical. On pedigreed seed farms, hand rouging is a standard procedure and may be used in broad regions as long as the infestation is not severe.
Summer fallow
Summer fallow is a practice that helps prevent soil erosion, manage weeds, and preserve moisture, nutrients, and crop residue. Perennial weeds are best controlled by summer fallow. Tillage encourages weed seeds to germinate, which means that it also helps reduce the amount of weed seeds in the soil. Weed flushes are managed using pesticides or tillage as they emerge. In situations where tillage is ineffective or when soil erosion is a concern, use herbicides. Use caution while using summer fallow since it increases salinity, erosion, and the loss of organic matter. Wide-sweeping field cultivators cut the roots of both annual and perennial weeds. A rod weeder will pierce the soil once it has been disturbed, effectively controlling annual weeds while minimizing moisture loss. Blade cultivators are useful in arid regions where less disturbance of the soil is preferred. till the calm, hot, and dry weather arrives. Summer fallow for one year will lessen but not completely eradicate weed issues. Weed seeds that have gone dormant will still sprout and appear in the following years.
Tillage
Tillage easily gets rid of annual weeds as well as biennial weeds with short tap roots and perpetual seedlings. It is essential to holistic weed management. It is simpler to manage younger weeds. The degree of soil disturbance has a direct bearing on tillage efficacy. Tillage has a larger impact on weed control. The residue cover, soil type, soil moisture, growing conditions, and weed development all influence the tool selection. While blade tools, like the Noble or Victory blade cultivators, can reduce waste, they are not very useful in chilly, damp weather. Plant residue-burying implements work well in damp environments but raise the risk of erosion. In the Brown and Dark Brown soil zones, less tillage is preferable, especially after dry years that leave minimal residue cover and on sandier soil. Rod weeders and field cultivators are an excellent middle ground.
Pre-seeding tillage:
The majority of weed seeds germinate more readily when shallow tillage (less than 7.5 cm) is applied in the early spring. The seedlings will be destroyed and a seedbed will be prepared by a second shallow tillage. If there is a lot of crop residue, use an instrument with a disc shape. When there is less residue, a cultivator or rod weeder will operate. This method works well on weeds like hemp nettle, wild oats, and mustards that sprout in chilly soil.
Post-seeding tillage:
This method will manage weeds that come up with or soon after potatoes, sunflowers, and cereal crops. Post-seeding tillage should be done cautiously since it can occasionally result in serious crop damage. For example, post-seeding tillage using interrow cultivation for maize and vegetable production is less harmful than blanket tillage. Nonetheless, it is generally safe to rod weed cereal crops to remove early emergent weeds while the crop sprouts are still below the rod weeder’s depth. Crop damage will differ depending on the kind of soil, the crop, the depth of planting, and the weather at the time of tillage. The best soil for tillage is hard, somewhat deep soil that has had deeper sowing. If post-seeding tillage is used, some crop loss is unavoidable and the grower should accept this fact.
Post-emergence tillage:
One can harrow wheat and barley after emergence if they are sown 8 to 10 cm deep and up to 25% heavier than usual. Before tillers develop, till between the first and fourth leaf stage. Parallel to the seed rows, light harrows can be drawn gently. Delaying crop maturity by at least two or three days can be achieved by post-emergent tillage with a harrow. If crop stress is present, do not tillage. More harm will result from this in a dry spring than the weeds themselves could ever do. In comparison to wheat, barley is more vulnerable to harm. Because straw clogs harrow and severely damage crops, post-emergent harrowing is not advised in areas with a high rubbish cover. Most of the time, herbicides are a superior substitute.
Inter-row tillage:
In row crops like potatoes and sugar beets, tillage can help control the weed population. Early and light tillage is recommended for the first time. If necessary, further passes may be made. Be cautious to prevent harm to your crops.
Fall tillage:
Early autumn tillage can be used to suppress winter annual seedlings as well as some perennial weeds. To keep your stubble in place in the Brown soil zones, use a blade cultivator. The remaining soil zones can be worked using field cultivators. If there is little stubble, wait till early the next spring and avoid autumn tillage. The kind of weed determines when to do autumn tillage. Autumn tillage is often carried out between crop harvest and soil freeze-up. For winter annuals, fall tillage and fall herbicide applications work quite well and need to be included in most weed management plans.
Grazing
Grazing does the same thing as mowing in terms of weed management. Preventing the formation of seeds is the primary goal of weed management. Grazing needs to stop the formation of seeds to be effective. As a result, while designing a grazing program, the age of the target weed is crucial. When weeds are young, they are most edible, and as they become older, they become less edible. Grazing needs to begin before seeds develop and while weeds are still edible. Few things can be accomplished by grazing as much as by mowing. This will vary depending on the grazing animal, the grazing method, and the target weed. Because grazing animals are often unavailable when needed, and because fencing and management are frequently insufficient or inappropriate to guarantee that top growth and seed production are restricted, many grazing plans fail to effectively control weeds.
The grazing system ought to minimize the grazing animal’s options. Successful systems have been implemented that use herded sheep and goats and short-duration cattle grazing. For a brief period, a high density of animals per unit space is referred to as short duration. The capacity of weeds to be palatable to grazing animals determines selectivity. Growing older plants lose some of their palatability. As a result, when weeds are at their most appetizing early in the season, you should begin to graze.
The type of weed, its age, the availability of animals for grazing, and the animal’s nutritional needs should all be taken into account when selecting a grazing animal. Every animal species typically has a distinctive, favored diet. Sheep like broader-leaved plants, including a lot of weeds, since they are intermediate feeders. Sheep steer clear of thick grass, debris, and plants. Unlike other domestic animals, sheep may change their diet to include more grass or browse. Sheep are probably the finest animals to test on many problematic weeds because they are utilized to collect weedy plants more frequently than other species.
Trap Strips
Crops that are particularly appealing to insects might be planted in strips around fields. Insecticides or cultural methods might be used to target and eliminate the pest insects in this area. These visually appealing crops might just be the same crop planted at a different period, or they could even be weeds or volunteer crops. Adult maize borer, for instance, lays its eggs in the highest plants. Corn borers are concentrated in trap strips that are sown earlier, to a quicker maturing variety, or adjacent to a grassy strip, tramline, or headland. These strips also effectively regulate the remaining portion of the field.
Moreover, trap strips work well against wheat stem sawflies. To lay their eggs, sawflies will only fly as far as is required. When sawflies are sown around a field, they will deposit their eggs in trap strips made of a solid-stemmed, resistant type. In the solid stem, larvae cannot live. To make the stems more developed and hence more appealing to females who lay eggs, sow sawfly trap strips earlier than the main crop. Trap strips reduce erosion, increase soil moisture, and overwinter the survival of fall crops and perennial crops.
Fire
It is not advisable to use fire for pest control. Since the temperature at ground level is rarely high enough to damage pests in the soil, it is frequently unsuccessful. Crop waste and organic debris that may be absorbed into the soil are destroyed by fire. If agricultural residue is destroyed by fire, the soil may become more prone to erosion. For helpful insects, fire may be very harmful. While beneficial insects hibernating close to the soil’s surface may be killed by fire, healthy pest larvae and pupae may not be destroyed.
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