296 Diseases of Truck Crops 



States. According to Stevenson' the trouble ap- 

 pears as indefinite sooty patches (fig. 54 c) on the 

 lower surface of the leaves. This saps the vitality 

 of the foliage, causing it to turn yellow and to drop 

 oflf prematurely. Great care should be exercised not 

 to allow the above disease to gain a foothold in the 

 United States. 



Wilt 



Caused by Fusarium malvacearum Taub.* 



Wilt is perhaps the main drawback to okra culture. 

 The disease is found in Ught sandy soils, and some- 

 times seems to work hand in hand with root knot. 



Symptoms. The disease does not seem to attack 

 young seedlings. It is common on older plants, which 

 however remain stunted as the disease works slowly. 

 In severe attacks, however, the lower leaves wilt, 

 droop, dry, and fall off. This is followed by a droop- 

 ing, wilting, and falling off of the upper foliage, leav- 

 ing thus a bare stalk, which eventually dries up. On 

 pulling up a diseased plant, we find that the root 

 system is apparently sound. But on splitting a 

 diseased root and stem lengthwise the interior fibro- 

 vascular bundles are fovmd to be brown, indicating 

 that the seat of the trouble is there localized. 



The Organism. Unpublished work by the author 

 has definitely established that okra wilt is caused by 



' Stevenson, J. A., Jour. Dept. Agr. of Porto Rico, i : 93-1 17, 1917. 

 ' From unpublished work by the writer. 



