ENEMIES OF RICE 369 



IV. ENEMIES. 



518. Weeds. — Perhaps the most serious menace to rice cul- 

 ture is the /growth of weeds. This is especially true where rice 

 is grown without cultivation, and where the water comes from 

 str-eams which abound in weed seeds and readily disseminate 

 them. 



Dodson gives the following list of weeds which have proven most menacing to 

 l-.he rice fields : 1 



(i) Red rice {Oryza sativa var. rufipogoti). 



(2) Large indigo, straight indigo, coffee weed, senna, long podded sesban 

 \Sesba7i inacrocarpa Muhl.). 



(3) Curly indigo, sensitive joint vetch {Aeschynomene virgi?t{ca (L.) B. S, P.). 



(4) Tadpole grass, wiggle-tail, spear grass (Rhynchospora comiculaia A. Gray) 



(5) Bull grass I^Panicum agrosiidiforvie Larrk). 



(6) Smart weeds {Polygomim, especially P. acre II. B. K.). 



(7) Turtle back (Ct>;«;«^//«rt cvV^zw/ca L.). 



(S) Alligator head {Diodia teres Walt, and Diodla vlrginiana L.). 



(9) Bird's e3-e {Sderia — several species). 



(10) Morning glory {Ipovioea tamtiifolid), 



(11) Water grass (^Paspahmt flnitans Kunth. and P. lirgatum) 



(12) Moss weeds. 



By far the most important and most serious one of these weeds is red rice. (505) 

 Few rice fields are free from it. By many planters red rice is believed to result 

 from volunteer plants growing from seeds of the cultivated white rice. It seems, 

 Iiowever, to be demonstrated that it is a distinct strain, and that red rice can be 

 obtained only from the seed of red rice. The two types readily cross, and the 

 results of the Louisiana Station indicate that the red rice has the greater influence 

 where crossing takes place. - 



Next to red rice in importance is the large indigo weed, both because of its 

 abundance and large size, ihe plant often growing to a height of fifteen feet, while 

 the stems sometimes attain a diameter of two to three inches. Like the curly 

 indigo, it is a leguminous plant. 



The alluvial lands are especially liable to become infested with weeds, so that as 

 a rule after two or three successive crops are raised, the soil must be devoted to a 

 cultivated crop or allowed to grow up with weeds for one or two years. The weeds 

 Ihat are injurious to the rice plant are water weeds. If the land is drained, the field 

 will grow up to dry land weeds and largely exterminate the water weeds, when the 

 field can again be cultivated in rice. This is considered by some to be good prac- 

 lice, since the land retains its fertility and the finest crop of rice is the first crua 



1 La. Bui. 61, 2d ser., pp. 402-436. 

 • La. Bui. so, 2ci ser. 



