GRAPE — LETTUCE 273 



remains hard and white or gray. Worst on hybrids with vinifcra 

 blood ; especially common on Delaware and Roger's hybrids. 

 Widespread in North America. 



Control. — Spray as for Black-rot. 

 Necrosis or Dead- arm Disease (FusicoccummYico/wm). —Attacks 

 shoots, and progresses from there to the old wood, causing a dry 

 rot and eventual death of the vine. 



Control. — Inspect canes at trimming time, and use care not to 

 leave those on which the brownish black spots are present. Train 

 up renewals from the root, and cut off the old stem below the dis- 

 eased area. 

 Ripe-rot {Glomerella rufomaculans) . — See under Apple, p. 263. 



Treatment as for black-rot is efficacious. 

 Shelling or Rattles. — Cause unknown. The berry breaks 

 squarely off at its juncture with the pedicle. The leaves on such 

 vines usually turn reddish brown about the margin. Powdery 

 mildew is sometimes responsible for shelling. 

 Control. — No method is known. 

 Hollyhock. Anthracxose {Colletotrichum malvarum). — Angular 

 brown spots on leaves and stems which spread, killing the entire 

 leaf. 



Control. — As for Rust. 

 Rust (Puccinia malvacearum) . — Attacks all parts of the plant, 

 causing reddish brown pustules on affected parts ; later leaving 

 deep pits ; may entirely destroy the leaves. It is abundant on 

 the common mallow or " cheeses." 



Control. — Eradicate the mallow ; pick off diseased leaves in 

 the fall, and burn all litter. Repeat in the spring, and spray new 

 growth thoroughly with bordeaux mixture, 4-3-50. Spray every 

 week until the flower-stalks are well developed. 

 Lettuce. Leaf Perforation (Marssonia perforans). — Dead areas 

 in the leaves which finally drop out. Also on veins of the leaves. 

 Control. — As for Rosette (p. 274). 

 Downy IVIildew {Bremia lactucce). — Y qWow spots on the upper 

 surface of the leaf, accompanied by a frosty growth on the opposite 

 side. 



Control. — Destroy infected plants. Keep water from the 

 leaves ; furnish water by means of subirrigation. 



