The tomato, in most regions, is not one of our most "pestered" crops. Although over thirty diseases of tomatoes are discussed in books and bulletins, most of them are only occasionally serious or are subject to definite control methods. Enemies are generally worse in the warmer climates.

Most home garden tomatoes and many commercial crops are grown without benefit of spray or dust. If trouble arises, county agent or college specialist can usually advise, suggesting methods suitable for local conditions.

Experience must, of necessity, be the guide in shaping a program and costs must be carefully balanced against results.

The principal measures that are widely used are seed treatment against damping off, use of resistant strains against fusarium wilt and application of bordeaux mixture against leaf blights.

As with all plants, thoroughness must be the watchword in spraying or dusting. Timeliness, choice of weather conditions so far as possible, and covering all surface lightly rather than throwing on heavy blotches of spray or dust all require careful attention.

Fusarium Wilt (Fusarium lycopersici) is perhaps the most serious of all the tomato diseases although it occasions little trouble in the more northerly states. It is troublesome as far north as New Jersey to Iowa.

The fungus winters in the soil, enters through the roots and blocks the water passages of the plant causing wilting, yellowing, and finally, death. Water vessels in the stem are discolored,—another means of identifying the disease.

Spraying or dusting are of no service since the fungus is within. Long time rotation and use of the many resistant strains are effective means of control.

Leaf Spot, Septoria Blight (Septoria lycopersici) causes heavy loss by destroying the foliage and so the fruit-making power of the plant. It also opens the fruits to sunscald. The spots appear as small dark water soaked areas which enlarge but little though they increase in number and turn brown. Tiny black dots, the fruiting bodies of the fungus, appear. The spores germinate only on moist leaves and the disease is spread by wind, rain, workers and the like. It winters on refuse of the tomato and related plants.

Fall plowing helps to control. Bordeaux spraying beginning in the seed bed and carried faithfully through the season will usually hold the trouble in check.

Late Blight (Phytophthora infestans) is the same fungus as the late blight of potatoes, affecting both foliage and fruit. It is often troublesome the first few weeks after plants are set out-of-doors. Clean soil in seed bed and bordeaux spraying are helpful.

Western Blight, Yellows, Curly Top,—cause unknown,—is prevalent in California. Leaves roll and become thickened and brittle, later turning a sulfury yellow. Veins become purplish. The trouble prevails in hot weather. The cause is likely a virus, similar to or identical with the curly top of beets. It is apparently spread by leaf hoppers. No satisfactory control has been devised though there is some promise in resistant strains.

Mosaic.—No organism has been definitely connected with the mosaic diseases of tomatoes, but they are highly infectious, being spread by means of what is called a "virus," which passes the finest filters. It is spread by insects, notably aphids, which carry plant juice, and in the handling of plants, but it does not persist in seeds or in litter. It is wintered on horse nettles and three species of ground cherries. Control suggestions include roguing affected plants, eliminating weeds, and controlling carrying insects. The symptoms are widely various, the most common being mottling of leaves, stunting and malformation of leaflets, which sometimes become fine ribbons or threads, curling, appearance of small brown dead areas, and spots and cracks on fruits.

Damping off is caused by various fungi in the seed bed which attack the stem near the surface of the soil and cause the plant to drop over and die. Clean soil, heating of soil, commonly called sterilization, and care in watering are all helpful. It is now common practice to dust seed with formaldehyde dust, or with red copper oxid or with an organic mercury disinfectant. If trouble is serious, a watering with semesan just before seedlings emerge may be helpful.

A government bulletin on "Market Diseases of Tomatoes" (Miscellaneous Publication 121, 1932) is an excellent summary with colored plates to help in recognizing the various troubles.

Insects

The Fruit Worm (Chloridea obsoleta) is probably the worst of the tomato insects, but is not prevalent in the North. It is the same as the corn ear-worm or the cotton boll-worm, and bores into green or ripening fruits. It winters in the soil and fall plowing is recommended for its control. Planting corn as a trap crop is also suggested. The Virginia Truck Experiment Station finds that the addition of two pounds of calcium arsenate to 50 gallons of the Bordeaux used for disease control helps materially.

Cut-worms (various species of the family Noctuidae) cause severe losses at the time of field setting. They winter in the soil and are worse when sod has been plowed under, or following other host plants. Poison bran mash is commonly used to combat them, using a spoonful to each plant. Hand picking and the use of paper collars are resorted to on a small scale. Well-hardened plants seem less subject to injury by these pests than tender plants.

Colorado Potato Beetle (Leptinotarsa decemlineata) can cause a world of damage to young plants. Arsenical spray or dust will ordinarily control them. The old-fashioned potato bug (family Meloidae), is reported as troublesome in Missouri. When they appear in droves, the only control is to drive them with brush. Arsenical spray or dust is of some value.

Flea Beetles (family Chrysomelidae) are the little black jumping fellows that perforate leaves in plant beds and in the field. They are also accused of injuring blossoms and reducing the set of fruit. Their attacks upon young plants are sometimes ruinous. Bordeaux with arsenical serves as a repellant. Dusting with nicotine sulphate dust is also suggested.

Green Tomato Worms, or Horn Worms (Phlegethontius sexta) are big, green fellows and have a great capacity for tomato foliage. Hand-picking and arsenical spray or dust are usual means of combat.

The stalk-borer (Papaipema nitela) is a slender caterpillar which is reported as serious in Indiana. No satisfactory control is suggested except clean culture around fields and pinching the stems to destroy the pest.