210 MANUAL OF GARDENING 
ammoniacal copper carbonate. The number of sprayings will vary 
with the season. Make the first application when the third leaf shows. 
Infections take place with each rain, and occur throughout the grow- 
ing season. The foliage should be protected by a coating of the spray 
before every rain. The new growth especially should be well sprayed. 
Hollyhock rust. — Fig. 212. Eradicate the wild mallow (Malva rotun- 
difolia). Remove all hollyhock leaves as soon as they show signs of 
rust. Spray several times with bordeaux mixture, taking care to cover 
both sides of leaves. 
Lettuce drop or rot. — This is a fungous disease often destructive 
in greenhouses, discovered by the sudden wilting of the plants. It is 
completely controlled by steam sterilization of the soil to the depth of 
two inches or more. If it is not feasible to sterilize the soil, use fresh 
soil for every crop of lettuce. 
Muskmelon diseases. — “Blight” is a very troublesome disease. 
The leaves show angular dead-brown spots, then dry up and die; the 
fruit often fails to ripen and lacks flavor. It is caused by the same 
fungus as is the downy mildew of cucumbers. While bordeaux has 
proved effective in controlling the downy mildew on cucumbers, it 
seems to be of little value in lessening the same disease on melons. 
“Wilt” is the same as cucumber wilt; treatment same. 
Peach diseases. — Brown-rot is difficult to control. Plant resistant 
varieties. Prune the trees so as to let in sunlight and air. Thin the 
fruit well. As often as possible pick and destroy all rotten fruits. 
In the fall destroy all remaining fruits. Spray with self-boiled lime- 
sulfur, S-S-50, to which 2 Ib. arsenate lead is added to the 50 gals., 
making first application as calyx is shedding, second 2-3 weeks later, 
third one month before fruit ripens, but omitting the arsenate. 
Leaf-curl is a disease in which the leaves become swollen and dis- 
torted in spring and drop during June and July (Fig. 213). Elberta is 
an especially susceptible variety. [Easily and completely controlled by 
spraying the trees once, before the buds swell, with bordeaux, 5-5-50, 
or with the lime-sulfur mixtures used for San José scale. 
Black-spot or scab often proves troublesome in wet seasons and 
particularly in damp or sheltered situations. While this disease at- 
tacks the twigs and leaves, it is most conspicuous and injurious on the 
fruit, where it appears as dark spots or blotches. In severe attacks 
