Cleavers

Galium aparine

Life Cycle

An annual that reproduces by seed. Cleavers was once considered a summer annual, but now there's evidence that it can overwinter and grow as a winter annual.

Emergence

The main flush of seedlings is in midspring with fewer seeds germinating throughout the summer.

Flowers

Cleavers flowers from June through August and seed is produced from August to freeze-up.

Reproduction

A single cleavers plant can produce 3,500 seeds. They are difficult to separate from canola seed owing to their similar shape and size. Cleavers seed becomes dormant in dry soil and can remain viable for one to three years. Seeds remain viable when eaten by animals. In fact, seed germination increases when seeds are recovered from animal droppings.

Planting contaminated canola seed has become the main source for spreading cleavers. Cleavers seed is a similar shape and size to canola, making it hard to mechanically separate cleavers seed from canola seed.

Because of this similarity, seed stock can be contaminated easily. According to the Canada Seeds Act, cleavers is a class 2, primary noxious weed seed. There is a zero tolerance limit for cleavers and cleavers seeds in all grades of pedigreed seed (foundation, registered or certified) for cereals, forage crops and oilseeds.

It is easily spread by harvesting equipment and in contaminated animal manure. The bristly seeds cling to the hair and wool of animals and people's clothing.

Competition

Cleavers can be very competitive because it clings to crop plants when growing towards light. The trailing plants can become tangled in moving parts of harvest equipment. Seed quality suffers when canola seed is infested with cleavers seed. Established forages compete well with cleavers.

Cleavers competes with crops for light, moisture and nutrients. Heavy infestations will cause yield reductions. In canola, one experiment showed a 20 per cent yield loss when cleavers were present at densities of 100 plants per square metre.

Management Strategy

Prevent seed production, especially in canola fields, and sow clean seed.

Plant certified seed. All grades of pedigreed seed (foundation, registered and certified) for cereals, forage crops and oilseeds, by their designations, must be free of cleavers seed. Planting with high quality seed produces more vigorous seedlings, which are better able to compete with weeds. Avoid contamination during transportation. Tarp trucks loaded with grain or screenings, even for short distances.

Clean tillage and harvesting equipment, paying particular attention to custom combine operations.

Compost contaminated manure. Cleavers infested manure should be composted for several months, so that the heating and decomposition process can destroy the seeds. Control cleavers in fencelines, road allowances, sloughs and other non crop areas. Mowing, grazing and spot spraying with a herbicide are all increasingly important sanitation methods, especially with reduced tillage.

Control Mechanisms

• Tillage
  Summer fallow - The number of cleavers seed can be reduced by summer fallowing. Till weed flushes to shallow depths to prevent seed production. Plants can re-root in moist soil, so tillage is most effective under warm dry conditions.
  
  Pre-seeding tillage - An early shallow tillage encourages germination of cleavers seeds. A second tillage, immediately before or at seeding destroys these seedlings. Seeding may be delayed, however. If delayed seeding is not possible, sow the crop early so that it gains a competitive advantage over cleavers.
  
  Post-seeding tillage - If pre-seeding tillage is performed then post-seeding tillage should not be necessary. Crops that are seeded early may not benefit from post-seeding tillage because crop growth may be too advanced before weed emergence is complete.
  
  Fall tillage - Fall tillage will encourage cleavers seeds to germinate and the seedlings will be killed by frost.
  
  
• Rotation
  Rotations that include summer fallow, cereals, and annual and perennial forages should help minimize cleavers populations. Winter annual cereals are especially effective. Do not grow canola on land infested with cleavers because cleaning cleavers seed from the crop is very difficult.
  
  In heavy cleavers infested fields, crops such as barley and wheat will compete more vigorously with cleavers than oilseeds and pulses. Rotating cereals with canola is an important line of defense. Managing cleavers during a cereal rotation will have carry over effects that will help keep subsequent canola crops clean.
  
  In rotations to eliminate cleavers, avoid crops with no herbicide options, i.e. clover, lentils and canola (With the exception of Pursuit-Smart canola for which Pursuit is a registered herbicide option). In fields with heavy cleavers infestations, planting perennial forages will help to reduce the populations to a manageable level.
  
  
• Seeding
  Spring seeding of land infested with cleavers should be either very early or delayed until after weed seedlings emerge.
  
  
• Mowing
  Because of the prostrate growth form of cleavers, mowing is not effective.
  

Crops	Herbicides	Staging		Weed Control/ Suppression	(Prices 1996 sugg. retail)
		Crop	Weed
Wheat spring wheat winter wheat durum Barley Oats
	Target Winter wheat	2-4 leaf(barley) 2-5 leaf(durum,oats and spring wheat) Spring: before crop is more than 30 cm tall	1-2 whorl 1-2 whorl	C C C	$6.50/acre
	Banvel+MCPA or 24-D Amine (high Banvel rate only, wheat only)	2-5 leaf	Before 3 whorl	C	$5.39/acre
	Dyvel Winter wheat	2-5 leaf Spring:15-25 cm tall before shot blade	2-3 whorl	S S	$4.43/acre
	Dyvel DS Winter wheat	3-5 leaf (wheat 2-3 leaf (barley) 3-4 leaf (oats) Spring: before crop is 30 cm tall	2-3 whorl 2-3 whorl 2-3 whorl	S S S S	$4.39/acre
	Mecoprop/Compitox	3 leaf to early flag leaf	2-4 whorl	C	$14.72 - 18.73/acre
	Refine Extra Refine Extra+MCPA or 2,4-D Amine	2 leaf to flag leaf full 3 leaf to expanded shot blade	1-3 whorl 1-3 whorl	S S	$4.95/acre
Canola	Edge	Apply at the recommended rates and timings as it pertains to soil texture and organic matter.		S	$11.66 - 20.34/acre
Triazine Tolerant Canola	Bladex Liquid(TTC)	1-4 leaf	1-2 whorl	C	$12.19/acre
Pursuit-Smart Canola	Pusuit	1-4 leaf	Up to 4 whorl	C	$18.25/acre
Field Peas	Basagran	After 3 pairs ofleaves (or 2-5nodes)	1-3 whorl	C	$19.00 - 25.00/acre
	Edge	Apply at the recommended rates and timings as it pertains to soil texture and organic matter.		S	$11.66 - 20.34/acre
	Pursuit	Up to and including 6 node	Up to 4 whorl	C	$18.25/acre
Flax	Basagran	Soon after 5cm		C	$19.00 - 25.00/acre

Seeds
Flower
Stems
Plant	Seedling	Mature