Cyanthillium cinereum (L.) H.Rob.

China: Cyanthillium cinereum flowers and fruits all year round.
Mayotte: Cyanthillium cinereum flowers from October to May and fruits from November to June.
Nicaragua: Cyanthillium cinereum flowers and fruits all year round.
West Indies: Cyanthillium cinereum flowers and fruits all year round.

Comoros:  Cyanthilium cinereum is present in the three islands, on roadsides, in areas of low and medium altitude up to 800 m.
French Guiana: Fairly common species in vegetable and fruit growing plots. Small annual ruderal very common in non-flooded environments, such as the banks and dikes of the Mana polder.
Madagascar: Species widespread throughout the island, from the coast to Central Highlands. Ruderal species and weed of rainfed crops.
Mauritius: weed common on roadsides, gardens, cultivated fields and fallow, brushwood, it preferentially develops in shady sites.
Mayotte: C. cinereum is a very common species in all degraded environments (crops, wastelands, roadsides, cities, rubble).
New Caledonia : A species able to colonize a wide range of open and disturbed places.
Nicaragua: C. cinereum is a ruderal species common in degraded environments in the Atlantic zone, from 0 to 150 m altitude.
Reunion: C. cinereum is common everywhere in Reunion, both in cultivated fields and in the gardens, at low or medium altitudes (0-1000 m).
Seychelles: Common species present at all altitudes.
South Africa: Cyanthillium cinereum is a common weed in crops and disturbed land, as well as in woodland and grassland at lower altitudes.
West Indies: Cyanthillium cinereum is a very ubiquitous arval and ruderal species, at altitudes of 0 to 1000 m.

Local harmfulness
 
Benin: rare and scarce.
Comoros: Cyanthilium cinereum infests at an early stage vegetable crops. It is also present in cassava crops and wasteland.
Madagascar: low to medium frequency species but often very scarce.
Ivory Coast: common and scarce.
Ghana: frequent and scarce.
Mali: frequent and scarce.
Mauritius: A common weed of sugarcane crops where it competes poorly with young stems.
Mayotte: Cyanthillium cinereum is a very frequent weed in food crops. It can be present in pineapple and vegetable crops. It is found in 29% of cultivated plots. It is very abundant in the northern zone of the island.
New Caledonia: This species is not an important weed of pastures, but in some situations it may be associated with other minor weeds in a community of unpalatable or unpalatable species whose abundance contributes to pasture degradation and decreases the production of forage species.
Nigeria: rare and scarce.
Reunion: C. cinereum is able to infest all kinds of cultures. It is present in nearly 30% of cultivated plots of the island, but never abundant, its recovery never exceeds 15%.
Seychelles: Species often locally abundant as naturalized weed of crops and plantations. In some cases, it can become a serious weed in vegetable and underground cultures.
Senegal: rare and scarce.

Global control

For weeding advice for broadleaf annual weeds of irrigated rice and lowland in Africa, visit: http://portal.wiktrop.org/document/show/19

Local control

New Caledonia: It is advisable to prevent the spread of the seeds of  Cyanthilium cinereum which can be more or less perennial by uprooting of the isolated individuals. On persistent stands, after slashing with rotary cutters, we can carry out a targeted spray herbicide treatment on isolated spots. Traditional active ingredients, such as 2,4-D (see table of treatments), are preferred because of selectivity to grasses.

 

Herbarium pictures ReCOLNAT for Vernonia cinerea : https://explore.recolnat.org/search/botanique/simplequery=vernonia%2520cinerea