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, 8-8-50, to which 2 lb. 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 distorted 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 Jose scale.

Black-spot or scab often proves troublesome in wet seasons and particularly in damp or sheltered situations. While this disease attacks the twigs and leaves, it is most conspicuous and injurious on the fruit, where it appears as dark spots or blotches. In severe attacks the fruit cracks. In the treatment of this disease it is of prime importance to secure a free circulation of air about the fruit. Accomplish this by avoiding low sites, by pruning, and by removal of windbreaks. Spray as for brown-rot, with lime-sulfur, 8-8-50.

Yellows is a so-called "physiological disease." Cause unknown. Contagious, and serious in some localities. Known by the premature ripening of the fruit, by red streaks and spots in the flesh, and by the peculiar clusters of sickly, yellowish shoots that appear on the limbs here and there (Fig. 215). Dig out and burn diseased trees as soon as discovered.

Pear Diseases

Fire-blight kills the twigs and branches, on which the leaves suddenly blacken and die but do not fall. It also produces cankers on the trunk and large limbs. Prune out blighted branches as soon as discovered, cutting 6 to 8 in. below the lowest evidences of the disease. Clean out limb and body cankers. Disinfect all large wounds with corrosive sublimate solution, 1 to 1000, and cover with coat of paint. Avoid forcing a rapid, succulent growth. Plant the varieties least affected.

Pear scab is very similar to apple scab. It is very destructive to some varieties, as, for example, Flemish Beauty and Seckel. Spray three times with lime-sulfur, 1-50, or bordeaux, 3-3-50, following the general methods employed for apple scab.

Plum And Cherry Diseases

Black-knot is a fungous disease. The spores of the fungus are carried from tree to tree by the wind and thus spread the infection. Cut out and burn all knots as soon as discovered. See that the knots are removed from all plum and cherry trees in the neighborhood.

Leaf-spot is a disease in which the leaves become covered with reddish or brown spots and fall prematurely (Fig. 211) ; badly affected trees winterkill. Often, the dead spots drop out, leaving clear-cut holes. Bordeaux, 5-5-50, or lime-sulfur, 1-40. For cherries, four applications : first, just before blossoms open; second, when fruit is free from calyx; third, two weeks later; fourth, two weeks after third. In plums it may be controlled by two or three applications of bordeaux, 3-3-50, or self-boiled lime-sulfur. Make the first one about ten days after the blossoms fall and the others at intervals of about three weeks. This applies to European varieties. Japan plums should not be sprayed with bordeaux.

Potato Diseases

There are different kinds of potato blight and rot. The most important are early blight and late blight - both fungous diseases. Early blight affects only the foliage. Late blight kills the foliage and often rots the tubers. Two serious troubles often mistaken for blight are: (1) Tip burn, the browning of the tips and margins of the leaves due to dry weather; and (2) flea-beetle injury, in which the leaves show numerous small holes and then dry up. The loss from blight and flea-beetles is enormous - often, one-fourth to one-half the crop. For blight-rot and flea-beetles spray with bordeaux, 5-5-50. Begin when the plants are 6 to 8 in. high and repeat every 10 to 14 days during the season, making 5 to 7 applications in all. Use 40 to 100 gal. per acre at each application. Under conditions exceptionally favorable to blight it will pay to spray as often as once a week.

Scab is caused by a fungus that attacks the surface of the tubers. It is carried over on diseased tubers and in the soil. In general, when land becomes badly infested with scab, it is best to plant it with other crops for several years. (See page 190).

Raspberry Diseases

Anthracnose is very destructive to black raspberries, but not often injurious to the red varieties. It is detected by the circular or elliptical gray scab-like spots on the canes. Avoid taking young plants from diseased plantations. Remove all old canes and badly diseased new ones as soon as the fruit is gathered. Although spraying with bordeaux, 5-5-50, will control the malady, the treatment may not be profitable. If spraying seems advisable, make the first application when the new canes are 6 to 8 in. high and follow with two more at intervals of 10 to 14 days.

Cane-blight or wilt is a destructive disease affecting both red and black varieties. Fruiting canes suddenly wilt and die.' It is caused by a fungus which attacks the cane at some point and kills the bark and wood, thereby causing the parts above to die. No successful treatment is known. In making new settings, use only plants from healthy plantations. Remove the fruiting canes as soon as the fruit is gathered.

Red-rust is often serious on black varieties, but does not affect red ones. It is the same as red rust of blackberry. Dig up and destroy affected plants*

Rose Diseases

Black leaf-spot is one of the commonest diseases of the rose. It causes the leaves to fall prematurely. Spray with bordeaux, 5-5-50, beginning as soon as the first spots appear on the leaves. Two or three applications at intervals of ten days will very largely control the disease. Ammoniacal copper carbonate may be used on roses grown under glass. Apply once a week until disease is under control.

For mildew on greenhouse roses, keep the steam pipes painted with a paste made of equal parts lime and sulfur mixed up with water. The mildew is a surface-feeding fungus and is killed by the fumes of the sulfur. Outdoor roses that become infested with the mildew may be dusted with sulfur, or sprayed with a solution of potassium sulfide, 1 oz. to 3 gal. water. Spray or dust with the sulfur two or three times at intervals of a week or ten days.

Strawberry Leaf-Spot

The most common and serious fungous disease of the strawberry; also called rust and leaf-blight. The leaves show spots which at first are of a deep purple color, but later enlarge and the center becomes gray or nearly white. The fungus passes the winter in the old diseased leaves that fall to the ground. In setting new plantations, remove all diseased leaves from the plants before they are taken to the field. Soon after growth begins, spray the newly set plants with bordeaux, 5-5-50. Make three or four additional sprayings during the season. The following spring, spray just before blossoming and again 10 to 14 days later. If the bed is to be fruited a second time, mow the plants and burn over the beds as soon as the fruit is gathered. Plant resistant varieties.

Tomato Leaf-Spot

The distinguishing character of this disease is that it begins on the lower leaves and works towards the top, killing the foliage as it goes. It is controlled with difficulty because it is carried over winter in the diseased leaves and tops that fall to the ground. When setting out plants, pinch off all the lower leaves that touch the ground; also any leaves that show suspicious-looking dead-spots. The trouble often starts in the seed-bed. Spray plants very thoroughly with bordeaux, 5-5-50, beginning as soon as the plants are set out. Stake and tie up for greater convenience in spraying. Spray under side of the leaves. Spray every week or ten days.