436 



IOWA DEPARTMENT OF AGRICULTURE 



Control. Land that has grown an infested crop should not be planted 

 to cauliflower or cabbage for a period of three or four years. It is 

 well to practice a three or four year rotation and burn all infested 

 cabbage stumps and other refuse. The seed should be treated before 

 it is planted and the seed bed should be on land that has not grown 

 cabbage for many years. If such soil is not readily available sterilize 

 it as described later. 



BLACK-KOT 



Black-rot attacks cabbage plants in all stages of their development, 

 either in the seed bed or in the field. It is caused by a bacterial or- 

 ganism which gains entrance to the plant thru the water pores at the 

 margins of the leaves. As the disease spreads from the point of in 

 fection toward the mid-rib the leaf becomes yellow and the veins black. 

 Infection may also occur from injuries made on the foliage by insects. 

 When a plant is badly diseased the veins in the stem become black. 

 A badly diseased plant under favorable conditions wilts and dies withm 

 a few days. Black-rot flourishes when the weather is hot and damp. 



Control. Exercise the same precautions as given for black-leg. 



CLTXB-EOOT 



Club-root is not generally distributed in Iowa but has been found in 

 a severe form in one locality. This emphasizes clearly the necessity of 

 guarding against this disease in any given locality. In many places In 

 the east club-root is a serious menace to cabbage. 



Club-root attacks only the roots of plants. It is caused by a slime 



mold that lives in the soil. If 

 plants are attacked when young 

 they die within a short time, 

 while in older plants the leaves 

 turn yellow and wilt. Out- 

 growths or galls are found on 

 the roots as shown in fig. 2, thus 

 the common name, club-root. 



Control. There is a great deal 

 of difference in the susceptibility 

 of the various varieties of cab- 

 bage to this disease. The Hol- 

 lander, Large Late Flat Dutch 

 and Henderson's Early Summer 

 are quite resistant but no va- 

 riety escapes entirely. IWhen 

 land is infested with club-root it 

 may be controlled by applying 

 150 bushels of air-slaked lime 

 per acre. This should be worked 

 in the soil to the depth of six to 

 Fig. 2. Root system of cabbage plant ^^^q inches six months previous 



root?'' '"'"^ "^ destroyed by club ^^ ^^^ ^^^^.^^ ^^ ^^^ ^^^^^^^ 



CABBAGE YELLOWS 



Cabbage yellows is one of the most destructive cabbage diseases found 

 in Iowa and occurs quite commonly thruout the state. Often this dis- 

 e'ase destroys 95 per cent of a crop. Cabbage yellows is caused by a 

 fungous parasite that can live in the soil for many years once it be- 

 comes badly infested. The threads of the parasite gain entrance into 

 the plant thru the roots arid finally make their way into the stem and 

 leaves. The parasite interferes with taking up of water by the plant 

 which causes the leaves to turn yellow and fall away as shown in fig. 3. 

 This may take place with the young or nearly mature plants. This 

 disease is most active when the weather is hot, as in July. 



