Cotton plant is essentially a shrub native to subtropical and tropical regions inclusive of India, Africa, and Americas. There are four commercially grown species of cotton, namely: Gossypium hirsutum (90% of the world population); Gossypium barbadense (8% of the world population); Gossypium arboretum (<2%); and Gossypium herbaceum (<2%). Cotton was originally cultivated 7,000 years ago, and since then cotton textiles have been spun, woven, and coloured since pre-historic times. Cotton is a comparatively drought-tolerant and salt-tolerant crop that mainly responds well to irrigation (Hake et al 1996). Cotton crop grows well on several types of soil: red and gray loam with clay subsoil; sandy soils over clay; and rich, well-drained bottom lands, with the safest soils being medium loam. This paper aims to investigate cotton agronomy, the key cotton pests, and to outline suitable control measures to utilize in controlling these forms of pests, as well as to describe a proper integrated Pest Management program to deal with pests.
Integrated Pest Management (IPM) is the process that can be utilized to solve pest problems while at the same time minimizing risks to both environment and humans. IPM Programs essentially feature several components, namely pest identification, monitoring and assessing pest number and damage, guidelines for where management may be necessitated, preventing pest problems, and utilization of a combination of cultural, biological, chemical, and physical/mechanical management tools.
4.4.0 Before Planting Cotton Crop
4.4.1 Land Preparation and Seed
In preparing for cotton-planting, the first step entails disking the land thoroughly, breaking it with heavy plough, and harrowing the land until attainment of a fine and mellow seed-bed. It is important to highlight the most appropriate cultivating and seed techniques that are likely to play a central role in growing cotton plants and aiding crops to thwart and/or tolerate diverse pests, weeds, and diseases that can have a considerable bearing on the crop yields (Anthony & Mayfield 1994).
4.4.1. Tillage Methods
Pre-plant cultivation prior to planting is critical in controlling small weed seedlings and preparation of the bed for seeding (Coughenour & Chamala 2001). Furthermore, raising bed seed areas is critical to facilitating groove irrigation, safeguarding against soil erosion, enhancing drainage and soil temperature to minimize the spread of infectious fungal diseases.
Seeds to be used in the planting should be clean, untainted, devoid of pests, and mixed with powdery fungicides to safeguard them from fungal diseases. Cotton seeds should also manifest a good germination rate and should be disease-resistant. The condition of the seed during storage and management within storage have a strong impact on seed quality (especially with regard to moisture and temperature). It is advisable to use certified seeds and undertake seed delinting prior to planting or treatment with insecticides (as well as use of pre-emergence herbicides).
4.4.3. Removal Residues of Infested Crops
Residues of infested plants should be undertaken, and the crop residues should be burnt. It is essential to remove and destroy root rot affected crops to safeguard against the diffusion of harmful pathogens, insects, and weeds via isolating and burning such residues.
4.4.4. Weed Chemical Control
The cheapest method of cultivating a cotton crop centres on preventing weeds and grass from taking root rather than waiting to destroy them when they have taken root. Layby herbicides may be used to complement weed control availed by cultural practices, pre-plant pre-emergence, and early season post-emergence herbicides and mechanical weed control.
Pre-irrigation can play a critical role in assisting of transportation of salt of the soil and planting and removal of weeds prior to planting of the cotton plant. Usually, one or more irrigation events are necessary to aid cotton emergence owing to warm weather in the months of May/June. Pre-irrigation usually enhances management intensity and avails the capability to deliver fertilizers and activate herbicides.
It is essential to adopt judicious fertilizer and water management and, most importantly, avoid excessive utilization of nitrogenous fertilizers. Prior to planting the cotton crop, one can add precise amounts of fertilizers including MAP (N:P:K -9:22:0) or DAP (N:P:K -18:20:0). These fertilizers can be critical in compensating for any deficiency, which may manifest in the soil nutrition status, especially phosphorous, that is essential in making cotton plants grow actively.
4.5.0 During Planting
4.5.1 Seed Rate:
The recommended seeding rate for cotton is within the range of 40,000 - 45,000 plants per acre (Kohel & Lewis 1984). To gain this, it is recommend to employ warm germination and cool germination to determine the quantity of seeds dropped per foot of drill. Irrigated crops require close to 9-12 kg/ha or 9-12 cotton plants per meter of row. Dry-land crops require close to 5-9 kg/ha or 5-9 cotton plants per meter of row.
4.5.2 Planting Time
Early sowing is always advisable, the best moment of planting irrigated plants is from late September to mid November, while dry-crops are recommended to be planted from late November. It is always advisable to steer clear of early growing under wet conditions as they may render the crop to be highly sensitive to infections of seedling fungal and insect pests (Monaco et al 2002).
4.6.0 After Planting Crop
Gap filling and thinning can be undertaken during the vegetative phase of the crop. This action is frequently employed when cotton seedling emerges approximately 2-3 weeks subsequent to planting and when the soil is wet. Hand thinning is central to enabling seedlings grow actively by reducing excessive plant density, which minimizes any possible spread of fungal disease (Deguine et al 2009).
4.6.1 Removal of Weeds
Removal of weeds works to reduce competition between weeds and cotton plants as well as to manage some form of insect pests and plant diseases that manifest as secondary hosts (Ali et al 2005). Hand weeding with hoes can be a critical and effective ways of controlling weeds within the planted row, especially where removal with cultivation is difficult.
4.6.2 Applying Biological Control
Biological agents may entail predators such as big-eyed bugs, spiders, lady beetles, and minute pirate bugs, parasites, such as Cardiochiles, and disease, such as Neozygites fungal disease, that helps control aphid outbreaks (Kirkpatrick & Rockroth 2001). Utilization of available natural enemies including predators, parasitoids, and entomopathogens can play a critical role in assisting control of insect pests as well as pathogens of plant disease such as Bacillus thuringiensis (Barliner) bacterium (Gillham 1995).
4.7.3 Applying Chemical Control
Utilization of some effective pesticides is pertinent and could reduce the insect population, safeguard against plant diseases, and safeguard against the harmful effect of weeds. Some of the approaches that can be employed entail utilization of kill baits (Fitt 1994).
4.7.0 After Harvesting
4.7.1 Removal of Crop Residue
It is essential to terminate the plant at maturity as early as possible so as to circumvent rationing and safeguard against re-infestation of insects, disease, or pests. It is critical to make sure that the field remains without crop as they may harbour pests (Stewart 2010). The removal of plant residue can help control permanent weeds and safeguard their spread into whole crop fields.
4.7.2 Crop Rotation
It is essential to rotate cotton crop as required with other field to sustain soil productivity and minimize incidence of diverse cotton pests such as seedling disease, pink bollworm, Verticillium wilt, and nematodes (Fradin & Thomma 2006). This can be attained via planting other crops that are constructive hosts for some pests or are not favourable for key pests that attack cotton with subsequent growing season.
Cotton is a unique crop plant, and its distinct growth pattern renders it challenging to grow. Nevertheless, the crop grows in a somewhat predictable pattern. Growing cotton necessitates right conditions entailing right soil conditions, climate, and cultivation methods. Control of all pests, weeds, and disease is central to crop production practices.