The first visible sign of late blight rot in tomatoes is a small, greenish-brown, water-soaked place, usually at the edge of the stem scar. As the decayed spot gets larger, it changes from greenish brown to brown. Often a rusty-brown irregular line develops between the diseased and healthy tissue.

The fungus penetrates the walls into the seed cavity of the tomato and causes a complete breakdown of the fruit. Usually there is no visible surface growth of the fungus unless the weather is very humid. Then a white mold may appear over some of the larger lesions and in the stem cavity. The rate the decay develops varies with the temperature, but in the usual shipping conditions the fungus can make good growth. Tomatoes that reveal no decay when harvested may show decayed spots, one-half inch to 1 1/2 inches in diameter, after only 6 days in transit. The only way to avoid the development of late blight rot in tomatoes in transit is to stop harvesting fruit from blighted plants during wet weather. Satisfactory control of late blight in tomato fields may be had by thorough spray programs; that in turn will reduce the losses in transit and in the ripening rooms.

IN THE WATERMELON PRODUCING regions of the Southern States, stem-end rot often causes more decay of the fruit during transit and marketing than all other diseases combined. It is caused by a fungus, Diplodia, which lives on decaying plant debris and affects many crops in the Southern States.

It may be inconspicuous on melons during the growing season. Often no trouble is suspected until a report is received from the market that shows that a number of melons have decayed during transit. Nearly all of the decay occurs at the stem end because the fungus requires some kind of a wound, such as the cut stem, to enable it to enter the fruit. When melons are harvested, the cut stem bleeds rather freely; consequently when airborne spores alight on the moist tissue, germination and infection take place. The fungus passes quickly through the stem into the flesh of the fruit, and the decay progresses rapidly throughout the melon.

The first indication of stem-end rot is a brownish discoloration, shriveling, and softening of the stem. After decay progresses to the flesh, the rind tissues about the stem become water-soaked, greenish brown, and somewhat soft. In advanced stages of decay, the affected tissues of the melon become dark brown, sometimes almost black, and there is a surface growth of dark-gray mold. With age, the area about the stem attachment becomes wrinkled. There is an extensive development of black pustules, the spore-bearing bodies of the fungus.

Melons that seem free of infection when harvested may show stem-end rot extending 3 to 5 inches into the end of the fruits by the time they reach the market. It is impossible to grade out all contaminated fruits at the time of shipment because the decay is not evident then. An effective control of stem-end rot is obtained by leaving long stems on the melons when they are harvested in the fields, then recutting the stem when the melons are placed in the car, and painting the cut surface immediately with a copper sulfate paste. Before this treatment was developed, as many as half of the melons in some cars were lost on account of stem-end rot.

WATERY SOFT ROT, caused by the fungus Sclerotinia sclerotiorum, is a destructive disease of practically all kinds of vegetable crops. The fungus inhabits the soil to some extent in all vegetable-growing regions.

Watery soft rot is likely to be prevalent in crops grown in damp soils during moderately cool seasons. Plants that become infected in the field may survive and produce a marketable crop, but they harbor the fungus and serious decay often develops while the plants are in transit, storage, and at the market.

The causal organism is particularly damaging because it can grow at the temperatures ordinarily used during transit. It may continue to grow in cold storage at temperatures as low as 32 F. Wounds are not necessary for infection by it and consequently, when a few infected vegetables are enclosed in a package for shipping, it may spread from one plant to another.

All vegetables in the package may decay. In green beans and peas the fungus frequently spreads from one pod to another, so that by the time the commodity reaches the market there may be a large nest of decayed pods, held together by the prolific growth of the white, cottony mold characteristic of the fungus. This type of spread of watery soft rot also occurs commonly in crates of celery.

The decay is typically a soft, watery breakdown, which has no definite odor other than the characteristic odor of the juices that have been liberated from the plant tissue. In green vegetables like beans, peas, lettuce, celery, and cabbage, the decay is tan or brown, water-soaked, and soft. In root crops like carrots, turnips, parsnips, and sweetpotatoes, the decay is yellow or brown, water-soaked, and moderately soft. In advanced stages hard, black, oval resting bodies, the sclerotic, are produced.

No satisfactory control measure is known other than carefully sorting the diseased vegetables at the time of packing and shipping. Commodities harvested from fields known to be severely infected should be marketed as soon as possible. Vegetables known to be slightly infected may be held in cold storage at 32 for a few weeks, but even then the disease will continue to make some progress. They should therefore be marketed promptly.

G. B. RAMSEY is s a pathologist in charge of the Market Disease Laboratory in Chicago. He holds degrees from Indiana University and the University of Chicago. Dr. Ramsey joined the Department of Agriculture in 1919 after serving as assistant pathologist and extension pathologist in Maine.

M. A. SMITH holds degrees from Kansas State College, Iowa State College, and the University of Illinois. He joined the Department of Agriculture in 1931, and has conducted research on the storage, transit, and market diseases of fruits and vegetables at the Market Disease Laboratory since 1942.