Tomatoes also usually need some irrigation in late summer to keep them growing actively until cool weather arrives. Because of the very wet weather of late spring, tomatoes that were planted early were soon infected by early blight or other leaf diseases. If no controls were used, damage can be fairly severe at this time as leaves gradually yellow and die from the base of the plants upward.
If plants are not too far gone, the use of a fungicide as well as cleaning out dead and badly damaged leaves may help continue some production into the fall. Several fungicides can be beneficial for its control. Maneb is one commonly available and effective but if infection is fairly extensive, weekly applications may be necessary. Where this disease has been extensive, clean up as much of the fallen dead leaf pieces and be sure to dig or plow the soil in the area in fall.
Blossom end rot always seems to appear on tomato fruits in some gardens at this time of year. It is usually a result of moisture stress tied to low calcium in the soil, or to low calcium absorption brought on by acid soils with ammonium nitrogen fertilization. There is also some variation in varieties as to their tendency to develop it. It is not at all related to disease organisms as sometimes suspected. Increased irrigation or fertilization with a calcium nitrate fertilizer can help reduce the problem for the remainder of the season. If the problem is severe and these techniques do not seem to help, have the soil tested this fall. It may be that the soil acidity or calcium content needs to be adjusted for next season.
Tomato fruit rots are also often abundant this late in the season. The best control for these is quick removal of any fruits as soon as spotted fruits are seen. Prompt harvest of ripe fruit will also slow development of this problem. Cloudy spot is a condition in which numerous, small, whitish areas develop just under the skin of the tomato and can be seen on the surface. This is caused by the stink bug feeding on the young tomatoes. The insects are often not apparent, but may be hiding nearby and move quickly out of sight if disturbed. The bugs are shield-shaped and may be green or brownish. Tomatoes are still usable, but less attractive and may need to be peeled. Garden insecticides that kill sucking types of insects will be effective in controlling them. Control can still benefit the tomatoes currently forming, but those already damaged will not improve.
Virus diseases may also sometimes attack tomatoes. They might have been apparent earlier in the season, but may still be found. Mosaics cause curled, crinkled or narrow, spindly leaves. Growth may be stunted or yellowed. In some cases leaves become thickened and plants are excessively, bushy and compact while fruits are reduced or have excessive amounts of greening on the shoulders. In some cases, fruits will have green streaking throughout the fruits. Viruses are generally spread by insects, but can be spread by people working on the plants. Once plants are infected, there is no control and plants should be pulled and eliminated so the problem does hot spread.
If viruses have been detected, it is a good idea to check for weeds in the area. Some viruses, or the insects that harbor them, may be hiding in weeds nearby. Keep down nearby weeds to reduce this convenience for the insects. Avoid using tobacco products while working on tomatoes, tobacco carries some of the same viruses that infect tomatoes and it can be transferred. If the presence of virus is suspected, dip hands in whole or skim milk while working on tomatoes and keep hands moist at all times during planting or pruning.
Hot weather can prevent fruit set in many tomato varieties. If fruit formation has been reduced, this may be a cause. Set will gradually improve as days and nights become slightly cooler. If tomato wilts attacked the tomato planting earlier, there most likely is no longer a tomato planting to be tending. For next season, be sure to select varieties known to be wilt resistant and, if at all possible, plant tomatoes in a new location for several years before returning them to the wilt-infected area of the garden.