How to control cogon grass (Imperata cylindrica) with cover crops

How to control cogon grass (Imperata cylindrica) with cover crops

Short answer: Mucuna bracteata is the most effective cover crop for suppressing cogon grass (Imperata cylindrica) in tropical plantations. Its vigorous growth and dense canopy smother cogon within 6-12 months. For severe infestations, combine an initial herbicide spot-treatment with MB planting for lasting suppression without ongoing chemical inputs.

Why cogon grass is a serious problem

Imperata cylindrica, known locally as cogon in the Philippines, is one of the world's ten worst weeds. It spreads aggressively through rhizomes and wind-dispersed seed, colonizing disturbed plantation soils rapidly. Left unmanaged, cogon competes heavily with young palms and tree crops for water and nutrients, creates a fire hazard during the dry season, and costs plantation managers significant ongoing labor and herbicide expenses.

Traditional management relies on repeated herbicide applications (glyphosate) and manual slashing, both of which are expensive, labor-intensive, and provide only temporary relief. Cover crops offer a biological, long-term solution.

Cover crop effectiveness against cogon

Cover Crop Suppression Rating Time to Full Suppression Mechanism
Mucuna bracteata (MB) Excellent 6-12 months Dense smothering canopy, blocks light
Pueraria javanica (PJ) Good 12-18 months Dense ground cover, light exclusion
Calopogonium mucunoides (CM) Moderate 12-18 months Fast initial cover, less persistent
Calopogonium caeruleum (CC) Good 12-18 months Stoloniferous spreading, shade tolerance

Recommended approach: MB + PJ combination

For severe cogon infestations, the most effective strategy is a two-phase approach.

Phase 1 (Months 0-3): Spot-spray active cogon patches with glyphosate. Wait 2-3 weeks for die-back. Plant Mucuna bracteata seedlings (from polybags) at 2 m x 2 m spacing in the treated areas. This gives MB a head start without cogon competition.

Phase 2 (Months 3-6): Once MB is established and actively spreading, broadcast Pueraria javanica seed (4-6 kg/ha) in the inter-rows and areas where MB has not yet reached. PJ fills gaps and provides long-term cover as the canopy closes and MB naturally thins.

Within 12 months, the combined MB + PJ cover should have suppressed cogon to negligible levels. The ongoing cover prevents cogon re-establishment from rhizome fragments and windblown seed.

Frequently asked questions

How long does it take for cover crops to suppress cogon?
With Mucuna bracteata, expect significant cogon reduction within 6-12 months. PJ alone takes 12-18 months. The MB + PJ combination approach is the fastest biological method available. Complete elimination of cogon rhizomes may take 2-3 growing seasons.
Can cover crops alone control cogon without herbicide?
Yes, but establishment is slower and success rates are lower without an initial herbicide knockdown. In light cogon infestations, direct planting of MB can succeed. For heavy infestations (over 50% ground cover), the initial herbicide spot-treatment significantly improves cover crop establishment rates.
Will cogon come back after cover crops are established?
Once a dense, healthy cover crop stand is established, cogon re-invasion is rare. The cover crop blocks the light that cogon needs to regenerate from rhizome buds. However, if the cover crop stand is damaged (by fire, excessive pruning, or livestock grazing), cogon can re-establish in the gaps. Maintain cover crop health to prevent re-invasion.
What about using cover crops with coconut trees?
Cover crops work well under coconut. The wider spacing of coconut plantations (8-9 m triangular) gives cover crops more inter-row space and light. PJ is particularly well-suited for coconut plantations because of its moderate shade tolerance.
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Recommended seed: Mucuna bracteata (MB) and Pueraria javanica (PJ).