AGP - Rottboellia cochinchinesis
 

ROTTBOELLIA COCHINCHINESIS (Lour.) Clayton 

 

 

Family: Poaceae

Synonyms: Manisuris exaltata (l.f.)Kuntze, Rottboellia exaltata L.f.

Common names: Itchgrass, Corngrass, Prickle grass, Caminadora, Corredora, Sancaraña, paja peluda, Herbe à riz, Herbe à canne.An annual grass weed with a sturdy and erect culm, often tillering and rooting at the nodes, which can grow up to 3 m high. The inflorescence is a spike-like cylindrical raceme up to 15 cm long. The seeds are capsule-shaped containing grains.

Itchgrass currently occurs in more than 30 warm-climate countries of America, Africa, Asia and Oceania. The weed mainly thrives in moist permeable heavy-textured soils. According to the recent FAO Regional Workshop on Itchgrass Management (Managua, Nicaragua, May 1992), it is estimated that more than 3.5 million ha of crop areas are infested with itchgrass in Central America and the Caribbean.

The plant reproduces by seeds. A single plant may produce more than 3000 seeds. The seeds generally have some dormancy and fresh seeds require 4-5 months after-ripening before they germinate. Factors controlling dormancy include environmental factors and water-soluble phenols which inhibit germination. In warm weather conditions seeds can remain viable for over 2.5 years and at soil depths of 45 cm.

Methods to prevent itchgrass spreading to non-infested crop areas include the planting of clean certified crop seeds, the use of machines and implements free of itchgrass seeds and the total control of itchgrass patches in surrounding uncropped areas and along irrigation canals.

Deep cultivation during land preparation should be avoided as buried seed may remain viable for several years. Minimum tillage practices lead to more rapid depletion of weed seed.

In infested areas maize monocropping should be avoided. Soybean-maize rotation considerably reduces itchgrass infestation. Soybean and sweet potato have been recommended as effective preceeding crops in rotation with potatoes and beans for reducing itchgrass infestation.

Chemical control of itchgrass is not an easy task in several graminaceous crops. Many of the herbicides applied in these crops such as chlorotriazines, acetanilides, certain phenylureas such as linuron, and EPTC plus dichlormid do not control itchgrass. Crop areas repeatedly treated with these herbicides commonly have increased itchgrass infestations.

Soil-applied dinitroanilines such as trifluralin and pendimethalin, and amides, diphenamid and napropamide effectively control itchgrass in several annual crops. In broadleaf crops it is recommended to use foliar-applied graminicides such as fluazifop-butyl, diclofop-methyl, haloxyfop-methyl and quizalofop-ethyl. However, it should be noted that sethoxydim and clethodim have been found ineffective against itchgrass at their normal doses.

Oxadiazon combined with propanil as an early post-emergence treatment is recommended for itchgrass control in rice fields.

Determination of economic thresholds may be an aid in decision-making for costly chemical control. In Cuba, this threshold is equal to 5 plants of itchgrass/m² (6-8% of itchgrass cover) during the first 30 days after seeding of maize or planting of potatoes.

 

Crop plants commonly affected by itchgrass include sugar cane, maize, sorghum, upland rice, cotton, potato and vegetables. It competes for soil nutrients, water and light, and also serves as host for several pests and diseases common to graminaceous crops.

In upland rice, itchgrass is one of the most competitive weeds and its seeds contaminate the harvested rice, depreciating its value and causing further infestations.

In potato, season-long interference by itchgrass can cause losses of up to 12 t/ha. This weed is originally from South East Asia, and was introduced into the American continent during XX century,perhaps contaminating crop seeds (most probably rice) imported from Asia. Due to its rapid spread in Central America and the Caribbean it was called "Caminadora" (Walking Weed).

 

Countries: Belize, Cameroon, Colombia, Congo (Democratic), Costa Rica, Cuba, Dominican Republic, Eritrea, Guatemala, Honduras, Indonesia, Mexico, Nicaragua, Panama, Peru, Philippines, Thailand, Vietnam, Zimbabwe

 

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