THE EICE WATER-WEEVIL. 13 



If the soil (Trios out after the larva 1 have made an advance in growth, 

 they soon die. The practice of draining fields and allowing them 

 to dry enough to cause the death of the larva: was first proposed in 

 1881 by Col. John Screven, a rice planter in South Carolina, and was 

 indorsed by Dr. Howard after his investigation in the field in 1881. 

 Some of the rice growers in Louisiana and Texas have reported good 

 results from periods of draining, while others have claimed that the 

 plants suffered more from being deprived of water than from at- 

 tacks. Many growers therefore advocate deep flooding of fields as 

 the proper treatment of rice when infested by the weevil larvae. 



Different results of draining are mainly accountable to the extent 

 of damage done by the larva? at the time of releasing the water. 

 TThen the roots have been but slightly or not yet severely attacked, 

 draining seems to result very effectively in most cases by the reduc- 

 tion of the number of larvae to a minimum. Effectiveness depends 

 on the length of time that plants can stand without water and not 

 suffer from the want of it. Plants that have a fair hold of roots 

 show no ill effects of drying spells lasting from 5 to 10 days without 

 rain. In case of "heavy rain, drying should be carried on for some 

 davs longer or until the surface of the ground forms a dry crust and 

 begins to crack. This stage of drying has been found very effective in 

 causing the death of larvae, and the ground has still retained sufficient 

 moisture below the surface to sustain the plants that possessed a large 

 proportion of roots. 



On the other hand, when roots have become severely pruned, the 

 plants are unable to endure draining without being further impaired. 

 Instead, they need a plentiful supply of water in order that new roots 

 can be put out and growth resumed. The value of draining is de- 

 pendent upon the enforcement of the practice at the proper time, 

 which the grower can easily determine by making examinations of 

 the roots. Many growers object to draining on account of the waste 

 of water and the risk or difficulty of getting fields promptly flooded 

 again. If fields were so arranged that water could be turned from 

 one to another in succession or from early to late plantings, most of 

 the water could be utilized and the saving in the cost of pumping, 

 where this means of supply is employed, would be an item of consid- 

 eration. Other benefits arising from changes of water will be men- 

 tioned later. Continuance of flooding to enable plants to overcome 

 injury by larvae, instead of taking steps to destroy the weevils, will, 

 as Mr. Newell has inferred, probably lead to a regular increase of 

 the number of weevils until the point is readied where the insect 

 will make profitable rice culture impossible. Constant or extra flood- 

 ing does not in the least inconvenience the larvse, but makes condi- 

 tions even more favorable for them. Being the most practical method 

 of controlling the weevils, draining of fields is therefore highly im- 

 portant. 



