Pre-plant and pre-emergent herbicide options are used extensively by experienced chickpea growers. A spring herbicide application, either pre-seed or pre-emergent, is recommended. This provides early season weed control and may provide control of weeds for which no in-crop control is available. Special care should be taken to control perennial weeds in the fall prior to growing chickpeas.
Sulfentrazone (Authority®), can be applied either pre-plant incorporated or surface applied pre-emergent. On most acres, it is mixed with glyphosate in a pre-seed or pre-emergent application. If applied post-seeding prior to emergence, apply within three days of seeding to prevent crop injury when emerging. Authority® works through root uptake in the soil, meaning precipitation must follow application for proper activation and good weed control. Ten to 20 mm (.393 to .787 inches) of precipitation within 10 to 14 days is needed for optimum efficacy. If weeds start to grow prior to activation, the result will be poor weed control.
Authority® (sulfentrazone) absorption by plant roots increases as soil pH decreases. At a soil pH of 6.5 or less, which can occur even in localized areas of the root zone, greater sulfentrazone uptake can occur and explain unpredictable patterns of injury to crops.
Herbicide testing indicates that chickpeas are especially sensitive to many post-emergent herbicides registered for the control of broadleaf weeds in lentils or peas. Sencor® (metribuzin) herbicide is registered for suppression of some broadleaf weed seedlings in chickpeas. Application should take place at the one to three above-ground node stage (maximum crop height six cm or 2.4 inches) with best results when the weeds are small. Application past this crop stage can lead to significant crop injury.
Clethodim-based (Select®/Centurion®), Poast® Ultra, and Quizalofop-based (Assure® II/Yuma® GL) herbicides are registered for control of annual grassy weeds in chickpeas. Application should take place at the one to six leaf stage of the grassy weeds.
If weeds are present, control them early as chickpeas are not a competitive crop. Weed competition can severely reduce yield. If weeds have emerged, apply herbicides at early crop stages. This will improve weed control, reduce competition from the weeds, and usually reduces herbicide injury.
Non-herbicide options may be considered as well. Tillage can have a beneficial effect for control of some weeds, while having the opposite effect on others. For example:
Herbicide-resistant weeds: Herbicide choice should take into account herbicide rotation to slow the development of resistant weeds. Resistant weeds are troublesome in chickpeas simply because they are a less competitive crop and there are limited herbicide options. A few examples of herbicide-resistant weeds that are particularly troublesome for chickpea growers include Group 2 resistant kochia, wild mustard, and cleavers, as well as Group 1 and Group 2 resistant wild oats. Rotating herbicide groups away from Group 1 and 2 products, especially in rotational years where chickpeas are not grown, can help prevent or manage resistant weeds. Research indicates that alternating between two modes of action for wild oat control will double the number of years for resistance build-up, and alternating with a third mode of action will increase the time of resistance build-up to four times as long as for a single mode of action for wild oat control.
Use integrated control methods through the rotation, such as higher seeding rates, promoting quick crop emergence, and using herbicides only when economic thresholds are reached. Preventing kochia from setting viable seed for one or two years greatly reduces kochia populations in a field because the seed is short lived in the soil.
Minimizing crop injury to herbicides: During periods of crop stress the ability of the chickpea crop to tolerate herbicide application may be reduced. Crop injury can be reduced by waiting approximately four days after the crop stress occurs before applying herbicide, by maintaining water volumes at label recommendations, and by applying the product during the evening.
Chickpeas can be damaged easily by some herbicides registered for other crops. Sprayer tanks should be thoroughly cleaned before applying any crop protection product to lentils and care taken not to drift herbicides from other fields onto chickpea fields.
Alternatives to chemical weed control: Non-herbicide options may be considered, including tillage and higher seeding rates. Tillage may be a tool to reduce kochia populations. Burial of kochia seed to at least one cm or deeper can result in reduced germination or death of the germinated seed prior to emergence. Spring tillage, even minor, significantly increases the burial and resulting germination of false cleavers and catchweed bedstraw. Farmers should consider limiting spring tillage as part of an integrated weed management program for cleavers.
Post-emergent harrowing of chickpeas is not recommended as it can spread disease and cause severe mechanical crop injury.
Higher seeding rates can increase crop competitiveness against weeds and reduce maturity. However, an increase in crop canopy may lead to higher disease levels.