PEST
Aphids: These are those dense clusters of tiny insects you may see on the stems or new growth of your tomato plants. While small numbers are not a problem — don’t be afraid to crush them with your thumb — large infestations can gradually injure or even kill plants. Pinch off foliage where aphids are densely concentrated, and throw these discarded bits into the garbage, not on the ground. If the problem then seems manageable, release beneficial insects such as ladybugs or lacewings
Flea Beetles: A potentially devastating visitor, the flea beetle (so-named because it resembles and jumps like a flea) attacks from both sides: adults eat foliage, leaving numerous small holes, while larvae feed on roots. They’re not picky, these beetles; they’ll go for corn, cabbage, lettuce, and all members of the Solanaceae family: peppers, eggplant, potatoes, and tomatoes. Unless levels are very high, damage can be minimized and controlled by using preventative measures.
• Clear away or plow under weeds and debris, in which adults over-winter.
• Place yellow sticky-traps to monitor levels and capture adults.
• Use row covers. Young plants are more vulnerable to damage, so cover them to keep beetles off.
• Dusting plants with diatomaceous earth (a chalky stone composed of marine fossils, ground to powder) helps control adults feeding on foliage.
• Clear away or plow under weeds and debris, in which adults over-winter.
• Place yellow sticky-traps to monitor levels and capture adults.
• Use row covers. Young plants are more vulnerable to damage, so cover them to keep beetles off.
• Dusting plants with diatomaceous earth (a chalky stone composed of marine fossils, ground to powder) helps control adults feeding on foliage.
Hornworms: These destructive caterpillars are so big — three inches long or more — that it would seem to be easy to control them just by picking them off. And so it is, sometimes. The problem is that their pale green color provides excellent camouflage, and the nymph and larval stages are far smaller and less obvious. If there are only a few, picking them off works well. (One site suggests spraying the plant with water, causing the caterpillars to, and I quote, “thrash around,” giving themselves away.) If there are more than a few, other measures may be called for. One of these is Bt, or Bacillus thuringiensis, an organic treatment that can control numerous other problems as well.
DISEASE
Damping Off: Caused by any of several viruses, damping off disease is a tomato problem that affects young, seemingly healthy seedlings that suddenly develop a dark lesion at the soil line, then quickly wilt and die. Cool, damp soil, overwatering, and overcrowding all increase probability of infection. Use clean potting soil and germination trays and tools to reduce incidence, avoid crowded seed beds, and monitor watering carefully during the first two weeks after sprouting.
Fusarium Wilt: Caused by a soil-borne fungus that targets Solanaceous plants (tomato, pepper, potato, eggplant), fusarium wilt often causes no symptoms until plants are mature and green fruit begins to reach its full size. At that point foliage, sometimes on only one side of the plant, turns yellow, and a sliced stem will show brownish, discolored tissue. Control includes crop rotation, so that the wilt organisms, deprived of a host, will die down in affected soils where it winters. Since cool, damp conditions favor infection, avoid spraying leaves, especially in cool weather. Use resistant varieties. use copper oxycholride @3g/liter of water with [email protected]/liter of water.
Mosaic Virus: There are actually several closely related viruses (the tobamoviruses) that cause the wilted, mottled, and underdeveloped fern-like leaves characteristic of the tobacco mosaic virus. All are spread by what are termed mechanical means: something or something that’s been in contact with the virus touches an uninfected plant, and voila — you’ve got an infected plant. Sanitation is therefore of the utmost importance, starting with never smoking near tomato plants, as tobacco can carry the virus. Infected plants should be destroyed. Back-yard plants purchased from a reliable nursery or grown from certified disease-free seed and handled in a tobacco-free environment by only one or two people, are unlikely to develop this disease.