Lentil Common Weeds and Weed Management

Lentil farmers face significant challenges in weed control, with weed competition being a primary threat to crop yield. Unlike cereal or oilseed crops, lentils have a thin crop canopy and are poor competitors against weeds, making them highly susceptible to yield loss, ranging from 20% to 40%. Lentil common weeds can drastically reduce yields and interfere with harvest. These issues are compounded by the development of herbicide resistance, limited herbicide options available for lentils, and the crop's small global market, which makes herbicide chemistries registered solely for pulses uncommon.

Long-Term Weed Control

An effective lentil weed management program requires long-term planning. Weed control efforts should begin in the year before planting, with crop rotation and field management playing key roles. Perennial weeds should be targeted during the fall prior to planting, either through tillage or with post-harvest applications of glyphosate.

Pre-seed and pre-emergence herbicide applications are also effective strategies, particularly when environmental conditions such as moisture and temperature are favorable. Lentil crops should emerge quickly to avoid injury from herbicide residues in the soil.

Common Weeds in Lentil Fields

Effective weed control in lentils necessitates an integrated approach that combines cultural and preventative measures along with the careful application of herbicides.

Common winter annual weeds in lentil fields include flixweed (Descurainia sophia), downy brome (Bromus tectorum), shepherd's-purse (Capsella bursa-pastoris), narrow-leaved hawk’s-beard (Crepis tectorum), blue bur (Lappula squarrosa), dog mustard (Erucastrum gallicum), and ball mustard (Neslia paniculata L), among others.
Common perennial weeds, include quack grass (Elymus repens), Canada thistle (Cirsium arvense), perennial sow thistle (Sonchus arvensis), toadflax (Linaria vulgaris), and dandelion (Taraxacum officinale).

Weed Management

Preventive Measures

Preventative measures start with selecting the right field, avoiding areas with known history of perennial weeds and weeds resistant to herbicides. Lentils are highly sensitive to herbicide residues from previous crops, so ensuring the field is clean and free of lingering herbicide residues before planting is crucial. The importance of sanitation in preventing weed spread cannot be overstated, and it is essential to clean seeding and harvest equipment regularly to avoid introducing weed seeds from other fields (or other parts of the field).

Cultural Measures

Crop rotation plays an important role in weed control. Lentil production is most successful when grown in rotation with cereals, such as wheat, which provide better competition against weeds and offer a broader range of herbicide options. Lentil fields following cereal crops tend to experience less weed pressure, and the benefits extend to the succeeding crop as well.

Tillage can also be used as a tool for weed control. Pre-seeding tillage is effective in controlling certain weed species, but it can reduce seedbed moisture. Specific weed species, such as kochia, are better managed through tillage as their seeds require burial to prevent germination. However, for lentil fields under no-till or minimum tillage systems, other measures like increased seeding rates or post-emergent harrowing may be required.

Post-emergent harrowing has been shown to be effective when the crop is very short, less than 10 cm (or 4 inches) in height. This method helps control weed seedlings but can lead to crop loss, which should be counterbalanced by higher seeding rates. To ensure success, harrowing should be done on warm, sunny days with dry foliage.

Chemical Measures - Herbicides

Herbicides can be used for lentil growers, but their use must be carefully managed to minimize crop damage and maximize effectiveness. Before applying any chemicals, you should consult a licenced agronomist. It is advised to always use approved products for lentil crops and permitted for cultivation in the country of production and exportation. You should always follow the label instructions and dosage recommendations.

Lentil crops, especially in their early stages, do not provide a competitive canopy, exposing weeds to sunlight and making them more likely to impact yields. The decision to apply herbicides should be based on economic considerations, weighing the potential yield loss against the cost of the chemicals and their application. To ensure the herbicide reaches the target effectively, sprayers must be thoroughly cleaned and maintained, and water volumes and spray patterns should be optimized.

Fields should be inspected regularly, both before planting and after crop emergence, to determine weed species and densities and select appropriate herbicides. Post-spray audits should also be conducted to ensure the effectiveness of herbicide treatments and allow for any necessary rescue treatments.

To minimize the impact of herbicide-resistant weeds, lentil farmers are encouraged to rotate herbicides with different modes of action and to scout fields carefully for symptoms of resistance. Repeated use of the same herbicide groups, particularly Groups 1 and 2, can lead to resistance in weeds like kochia, wild mustard, and cleavers.