Chickpea: Crop Protection

Weed Control

Chickpea is a poor competitor with weeds.

Considerations include:

• Post-emergent harrowing is not recommended, as it can spread disease and cause severe crop injury.
• Using the correct seeding date and optimum plant densities are the best ways to ensure the crop has the opportunity to compete with weeds.
• A pre-emergent burn-off with a non-selective glyphosate herbicide can be used to control winter annual and early emerging spring annual weeds.

Herbicide testing indicates that chickpea is especially sensitive to many post-emergent herbicides registered for the control of broadleaf weeds in lentil or pea. See the Guide to Crop Protection for herbicide options.

Controlling perennial weeds

It's important to control perennial weeds, such as Canada thistle or sow thistle, in the years prior to chickpea. Volunteer canola, mustard and flax are difficult to control, and rotations that include these crops should be avoided prior to chickpea production.

Low rates (280g ai/ha) of 2,4-D can also be used from mid-October until freeze-up to control broadleaf winter annual weeds such as stinkweed, shepherd's-purse and flixweed.

Chickpea is sensitive to the soil residues of a number of herbicides (see Rotational Considerations), and to herbicide drift. Producers should inform their neighbours about the location of their chickpea crops, and thoroughly clean their sprayer tanks before applying any crop protection product on chickpea.

Disease Control

Infected seed

A complex of pathogens can cause seed rot, seedling blight and root rot of chickpea, including species of:

• Pythium
• Fusarium
• Rhizoctonia
• Botrytis

Seed rots and seedling blights are most severe when soil is cool or saturated and seedling emergence is delayed.

Symptoms include:

• Infected seed may fail to germinate.
• Infected seedlings will usually turn yellow and then wilt and die.
• Stems may be girdled and discoloured at or just below the soil surface; roots may be rotten, allowing the plants to be pulled easily from the soil.

Kabuli chickpea is especially susceptible to rots due to its thin, zero-tannin seed coat. See the Guide to Crop Protection for seed treatment fungicides registered for control of seed rot and seedling blight caused by Pythium.

These seed treatments are not usually required with desi chickpea because of its thick, dark-coloured seed coat, which contains tannins that have a fungistatic effect against Pythium.

Rhizobium inoculants can be affected by seed treatments (see Seeding), so labels should be checked to ensure that the products are compatible.

Botrytis grey mould

Chickpea is also susceptible to botrytis grey mould, both at the seedling stage and in advanced stages. Botrytis grey mould of seedlings may spread down a seed row, resulting in a series of yellow or dead seedlings.

Botrytis grey mould is also favoured later in the growing season by dense canopies and moist conditions. Botrytis is usually most evident after flowering, and is common on pods, resulting in shrunken, discoloured seed. The infected area is often covered by a dark grey, fuzzy fungal growth.

Ascochyta blight

Ascochyta blight is a foliar disease that can completely destroy a chickpea crop. It is caused by a fungal pathogen (Ascochyta rabiei) that is both seed- and residue-borne.

Ascochyta blight of chickpea is much more aggressive than ascochyta blight of lentil or pea, and is caused by a different Ascochyta species.

Symptoms include:

• Tan or brown lesions on stems, leaves and pods.
  
  • Lesions may girdle entire stems, causing them to wilt and die.
  • Dark fruiting bodies, called pycnidia, are formed in the lesions.

The pycnidia ooze spores in wet and humid conditions. Spores are spread by rain,and infection is aided by weather with frequent showers. Plants will show lesions approximately four to seven days following infection. If weather turns warm and dry, infected plants may survive, but will be delayed in maturity and produce lower yields.

Reducing the risk of infection

Ascochyta blight is also seed-borne, so the use of disease free seed is critical. It is also capable of surviving for several years on crop residues in the soil. A minimum four-year crop rotation will reduce the risk of infection.

Other considerations

Another consideration in disease control is the selection of varieties with "fair" instead of "poor" or "very poor" ratings for ascochyta. A key goal of the Crop Development Centre chickpea breeding program is improved ascochyta blight resistance.

Research carried out at AAFC, Saskatoon, has identified 15 races of Ascochyta rabiei in Western Canada. This indicates the broad range of variation in the disease.

Both mating types of the pathogen causing ascochyta blight of chickpea have been identified in Saskatchewan. This allows for sexual recombination, and the potential change in virulence of the pathogen to overcome varietal resistance. The sexual stage also results in the development of air-borne ascospores, aiding in long-distance disease transmission

Early and regular scouting is essential. Research to date indicates that an early application in the seedling stage is most effective in preventing disease build-up in the field, regardless of which fungicide product is used.

See the Guide to Crop Protection for registered fungicides.

Researchers from Agriculture and Agri-Food Canada (AAFC-Saskatoon) found isolates of Ascochyta rabiei collected in Saskatchewan in 2003 with resistance to the strobilurin fungicide group. More recently, strobilurin-resistant isolates from southern Saskatchewan (samples collected in 2006) have been identified.

Reduce the risk of resistance build up

• Rotate the use of a strobilurin product (whether used solo or in a tank mix) with a non-strobilurin product,
• Use no more than two applications per year of any fungicide containing a strobilurin to the same field,
• Not use a strobilurin product as the last application of the season (to help reduce the risk of resistant strains from over-wintering).

For additional guidelines to reduce the risk of strobilurin resistance, refer to the North American Fungicide Resistance Action Committee (NAFRAC).

Sclerotinia stem rot

Chickpea grown in conditions of high rainfall and dense crop canopies is susceptible to sclerotinia stem rot. This disease is more common in crop rotations that include other susceptible broadleaf crops such as canola, mustard, lentil or pea.

Symptoms usually occur in patches, typically in heavier areas of the crop.

Infected plants are initially paler green and the diseased tissue may be covered by a white, cottony fungal growth. The plant later becomes bleached in colour and the infected area will easily shred apart, revealing small black fungal resting structures.

Insect Control

Chickpea leaves, stems and pods are hairy and secrete malic acid that makes the plant less attractive to insects.

Insects reported to be pests of chickpea in Western Canada include:

• Wireworms;
• Alfalfa loopers;
• Aerial or above-ground feeding cutworms (i.e. red-backed cutworms); and
• Grasshoppers in the early seedling development stage.

Leaf-mining larvae have been noted on lower leaves of chickpea, pea and lentil in recent years, with no notable effects on yield.

See the Guide to Crop Protection for registered insecticides.

Other considerations

Chickpea seedlings are also very attractive to rabbits and deer and may be grazed to economic loss.

Next: Chickpea Harvesting Considerations