Weed Control in Chickpeas, An Alberta Perspective

(Focus on Broadleaf Weed Control)

Beata Lees, P.Ag., CCA

ACE Specialist, Westco

Lethbridge, AB

Introduction (or know your crop and know your weeds):

• Chickpea (Cicer arietinum) is a member of the Leguminosae family. It originated in North Africa and the Middle East where they were first cultivated around 5000 B.C. Chickpea is a spring seeded, annual legume with an indeterminate growth habit and long taproot. Chickpea is a cool season crop grown typically as a winter crop in India, the Middle East, Australia and South, Central America. On the prairies, chickpea can be considered a warm season crop.

• There are two types or market classes, divided according to seed size. Desi are shorter stature with smaller seeds, darker, thicker seed coats, wrinkled and irregular in shape. Kabuli are later maturing than Desi. The larger Kabuli seeds are creamy coloured and have thin white (zero tannin) seed coats.

• Chickpea is best suited to daytime temperatures of 20-30 C and nighttime temperatures between 18- 21 C. Optimum germination is 10-15 C but Desi chickpea will begin germinating at soil temperatures as low as 5 C. The cotyledons remain below ground during germination and have the ability to re-grow if the top growth is damaged by frost. Optimal rainfall is 8-12 inches during the growing season. Chickpea is well adapted to the drier parts of the brown and dark brown soil zones of the prairies.

• Weeds are well adapted to local environment. Most germinate in early spring.

• Wild mustard and wild oats are vigourous competitors. Green foxtail, lamb's quarters, and wild buckwheat are less vigourous.

• Weeds compete with crop for nitrogen. Buckwheat, smartweeds and wild oats are high users.

• Weeds compete for moisture. Wild mustard, wild oats use 4X as much water as cereals.

• Light competition begins when plants begin to shade each other. Shading reduces green foxtail, wild oat competition. Heavy canopies inhibit germination.

• Bindweed, red root pigweed and green foxtail seedling emergence is associated with that first warm period the spring.

Other options are available and need to be explored:

• Warm season crop strategy. It is similar to that for growing corn on the prairies. Warm soil temperatures are required for crop germination while most prairie weeds germinate early to mid spring, then sporadically throughout the season. There is slow early growth in cool spring weather and low plant populations to compete with weeds. In corn, the objective is to remove and minimize weed growth for the first 6-8 weeks after the crop emerges. Control weeds by 3 weeks and prevents them up to 6-8 weeks.

• Systems approach using crop rotation: use of cool season grasses, aggressive crops can help with weed management in rotations. This strategy works with corn, safflower and beans. Plan to interfere with the weed's life cycle. Control of fall rosettes, like stinkweed, is important to discourage the early spring seed production.

• In zero till, good early weed control can decrease pressure from annual weeds after a few years, on the other hand reduced tillage favors weeds with vegetative reproductive capacity from underground roots and stems.

• Decrease N supply available for weeds. Plant chickpea into stubble with low nitrogen levels.

• Lengthen crop rotation intervals to reduce weed populations. This can help reduce the weed seed bank. For example kochia do not remain viable in the soil for more than a year, lamb's quarters will remain viable several years and dormancy is broken when weed seed is brought to the soil surface.

What we learned in 1999:

• Cool spring, cooler summer was a disadvantage for chickpeas. Early seeding caused some cold stress, uneven emergence and allowed weeds an early competitive start. Use of soil temperature, as a seeding decision tool is important.

• Damage from the use of Pursuit as a pre plant / post emerge showed up this year while in 1997 and 1998 injury reported was minimal. In several cases maturity was delayed 2-3 weeks. Herbicide damage was more prevalent in crops with cold stress likely due to slower crop metabolism and minimal root growth.

Western Canadian Research and Development in Chickpea Weed Control: past/present:

• Agriculture and Agri Food Canada: Ken Kirkland et al

• University of Saskatchewan, Crop Development Centre: F. A. Holm et al

• Alberta Agriculture: R. Esau et al; On Farm Demo's: B. Lees

• Farmer experiences

Results to Date:

• Injury: Basagran, Buctril M, MCPA, 2,4-D, Pardner, Odyssey, Pursuit.

• No injury this year: Lentagran, Dual.

• Unknowns: Corn and soybean herbicides being tested in Saskatchewan MUR trials.

Herbicide Use in Other Countries:

Australia and the U.S. use the following herbicides on chickpeas:

• Australia: - Pre emerge: Bladex, trifluralin, simazine.

- Post-emerge: Bladex, Tough (Lentagran), and Broadstrike.

• U.S.: - Pre emerge: Sonalin (Edge).
  • - Post emerge: Tough. Pursuit is not used much as growers have
    • sensitive crops in the rotation.

• Group 5 are some of the oldest herbicides around. Examples include atrazine. They vary in soil activity and usually work best under sunny conditions. Sencor, a PSII inhibitor, moves through the zylem. Symptoms include chlorosis at the leaf edges. The rapid disruption of cell membranes reduces herbicide movement, trapping them in a zone of death. Sencor is immobile in high organic matter and high pH increases mobility. It can be absorbed through the roots. Sencor works best, with the least crop injury, before the chickpea leaves open or at ground crack

Not registered yet: Edge:

• Group 3 (dinitroananlines) inhibits cell division and elongation in the meristematic regions, such as root tips. It affects roots more than shoots. Effects are stubby, pruned roots. Incorporation prevents volatilization and photo degradation. Herbicide selectivity is not based on metabolism. Symptoms include root swelling, where the cells enlarge without cell elongation. Edge binds more tightly to organic matter than clay particles. This causes it to be unavailable to control weeds. It is degraded by sunlight especially on warm days.

Not Registered: Pursuit: Issues include crop injury and crop rotation:

• Group 2 (imidazolinones) are inhibitors of acetolactate synthase (ALS). ALS is a key enzyme that is most active and most sensitive to inhibition in young meristematic regions of the plant. Protein synthesis is reduced and cell division is inhibited so the plant not only starves there is a toxic buildup. Selectivity is based on the plants ability to rapidly metabolize the herbicide before it becomes toxic. Weeds are controlled because they metabolize at a lower rate. ALS inhibitors are readily taken up by leaves and roots. As soil pH decreases, persistence increases with IMI's. Low organic matter increases adsorption. Degradation is favoured by high pH and high microbial activity.

Herbicide Observations/Comments:

• Pursuit: Company not supporting MUR in the brown soil zone due to potential crop injury and cropping rotation issues.

• Edge: moratorium

• Bladex: (cyanazine) Corn herbicide. Company phase out of herbicide started in 1996 and product manufacturing is stopping. Moisture needed for activation. Will leach on sandy soils. Not used on soils with more than 70% sand or less than 1% organic matter.

• Lentagran: (pyridate) Company is selling off the chemistry. Weeds controlled: lamb's quarters, redroot pigweed. Has shown activity on kochia, Russian thistle, cleavers. Is weak on mustards.

• Broadstrike: (flumetsylam) is not registered in Western Canada. It is a group 2 SU with cropping restrictions and limited weed spectrum used as part of a corn, soybean herbicide package. In Australia it causes yellowing and stunting in chickpeas. Weeds controlled mustards, pigweeds, kochia, lamb's quarters, wild buckwheat, nightshade, velctleaf.

• Simazine: (triazine family) Group 5. It is a corn and orchard herbicide. Soil breakdown is very slow. Prolonged hot, dry weather lengthens time residues remain in the soil. Leaching likely on sandy soils. Sensitive crops include cereals, peas, canola, beans…Incorporation is required.

• Dual: (metolachlor) group 15. Corn, bean, potato herbicide. Controls some grasses, nightshade. No wild oat control. Needs continuous moisture to work.

What's In The Future:

• Minor Use Registration Program: AAFC, AAFRD, U of S, CDC, SAF all involved in program. Need grower and company support to put forward a chemical for registration. It has to be a registered herbicide in Canada.

• Other potential issues: HACCP international standards. It is a program similar to ISO. Buyers, especially those in Europe, use it. There is more pressure from end use customers to show there is HACCP compliance. In Canada the CFIA is the governing body. You need grower records. It is already in demand in the bean and the potato industry.