PN-5223 



Figure 10. — A pole, wire, and string system for supporting yams. 



(50° C) water treatment for 30 to 60 minutes (2). Treatment of 

 the soils with DBCP^ at the rate of 28 to 112 kilograms per hectare 

 has been useful in Nigeria. 



Severe damage to tubers of D. rotundata and D. cayenensis 

 is caused by several kinds of grubs. These pests vary in incidence 

 and species throughout the Tropics but are especially bad in 

 Africa. Eteroligmus meles (Billb.), the greater yam beetle, passes 

 through its mating and reproductive cycle in swampy areas but 

 migrates to yam plantations for feeding. In Puerto Rico the 

 white grub, Lachnosterma sp., and Diaprepes abhreviatus often 

 damage tubers. Although beetles have been controlled by appli- 

 cation of insecticides to the soil, this is a risky practice. Insecti- 

 cides can be leached from the soil and contaminate water supplies, 

 and they can be ingested when the yams are eaten. Avoidance and 

 sanitation are preferable techniques. 



Rotting, closely associated with harvest injury, is the chief 

 cause of tuber loss in storage. It may be substantially reduced by 

 careful harvest and handling of tubers and by separation of in- 

 jured and uninjured tubers, with injured tubers being used first. 

 Warm, dry temperatures and aeration after harvest stimulate 

 healing of wounds and reduce subsequent rot. Tubers should not 



^ l,2-Dibromo-3-chloropropane. 



26 



