Smooth pigweed, scientifically known as Amaranthus hybridus, has become a significant problem in agricultural fields worldwide. This weed belongs to the Amarantaceae family and is an annual plant with broad leaves. Its tall and erect or bushy growth pattern makes it easy to identify. Smooth pigweed produces dense clusters of small green flowers that turn into seeds, completing their life cycle within a single growing season. In Swahili, it is commonly referred to as ‘Muchicha.’

Global Distribution of Amaranthus hybridus

Smooth pigweed is found in tropical and sub-tropical regions across the globe. It has spread to humid and sub-humid areas of Kenya as a weed. Native to parts of North and Central America, this weed has thrived due to agricultural practices and human activities, colonizing agricultural ecosystems in America, Europe, Asia, and Africa.

Ecological and Environmental Requirements of Smooth Pigweed

Smooth pigweed prefers altitudes ranging from 900 to 2600 meters above sea level. It thrives in shallow loam soils with adequate moisture and good soil contact for seed germination. Some seeds remain dormant when buried deeply but can remain viable for years and germinate when brought to the surface through cultivation. This weed adapts to various soil types, including sandy, loamy, alkaline, and saline soils, with a preferred soil pH between 6.0 and 7.5. It can survive in different climatic conditions, including cool, warm, humid, and dry environments, allowing it to colonize diverse regions worldwide.

Distribution in Kenya

Smooth pigweed is a common weed in western parts of Kenya but can be found throughout the country.

Adaptations for Survival

Smooth pigweed exhibits adaptability to different environmental conditions, including hot weather and drought tolerance. This adaptability enables it to colonize crops growing under varying conditions. The weed responds favorably to nutrient availability, particularly nitrates, which promotes its rapid growth and enhances competition for nutrients with cultivated crops. Its ability to elongate stems rapidly helps it avoid shading, ensuring it can compete with crops for sunlight. Smooth pigweed produces a large number of seeds, aiding its propagation and spread compared to crops.

Methods of Dispersal

This weed has various means of dispersal, such as irrigation, floodwater, tillage tools, tractor tires, manures, and soil clinging to footwear. These mechanisms increase the chances of its dispersal and colonization in numerous farms. Additionally, it possesses multiple dormancy mechanisms, leading to seed germination at different times throughout the year, ensuring the weed’s survival and making eradication challenging.

Negative Impact on Crops

Smooth pigweed hosts pest nematodes (Meloidogyne app) and several vegetable pathogens, including those responsible for early blight in potatoes and tomatoes (Alternaria solani), lettuce rot (Sclerotinia sclerotiorum), and southern blight (Sclerotium rolfsii). It can also transmit viral pathogens like Cucumber Mosaic Virus to crops. Moreover, smooth pigweed competes with crops for nutrients, water, and light, resulting in weakened crops and reduced yields. The weed’s seeds can contaminate crop yields, affecting the quality of the produce. Additionally, managing smooth pigweed requires significant investment in terms of capital and labor, increasing the overall cost of crop production. The weed’s growth can also block irrigation channels, further complicating agricultural operations.

Moiben Solutions for Smooth Pigweed Control

Moiben Crop Protection offers various approaches to eradicate smooth pigweed, depending on the specific crops affected. The weed can be found growing alongside crops such as maize, onions, carrots, beans, and many others. During land preparation for crop cultivation on non-cropped land, the following herbicides can be utilized:

1. WEMBE 200 SL: A non-selective post-emergence herbicide effective against both annual and perennial grasses and broad-leaved weeds, including smooth pigweed. It is applied during land preparation to clear all weeds.

2. CATAPULT 480 SL: Another non-selective post-emergence herbicide that controls annual and perennial grasses and broad-leaved weeds, including smooth pigweed. It is used during land preparation to eliminate all weeds.

3. HURRICANE 200% SL: A non-selective post-emergence herbicide specifically designed to control annual grasses and broad-leaved weeds, including smooth pigweed, in maize, sweet corn, baby corn, and sugarcane. It is applied between rows when crops reach a certain height.

4. BENTAGRAN TOP 240 EC: This selective early post-emergence herbicide targets annual grasses and broad-leaved weeds, including smooth pigweed, in common beans and French beans. It is applied when the weeds, particularly smooth pigweed, are actively growing.

These herbicides, when used in accordance with the recommended rates, help control smooth pigweed and other undesirable weeds, ensuring the well-being and productivity of crops.

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