Disease guide

Contact herbicides, those that affect only the tissues they contact, typically will cause chlorotic or necrotic spots on all parts of the plant. Multiple spots can result in deformation of the affected tissues. Systemic herbicides, those that are translocated in the plant, tend to cause a variety of symptoms, including stunting. These range from a general yellowing of the foliage to yellowing or necrosis of tissues in the center of the leaf, to a yellowing or necrosis of the leaf veins that may expand to the interveinal tissues. Systemic herbicides may also cause necrotic spots, leaf margin necrosis, twisting and upward or downward leaf cupping, as well as mild or severe deformation and swelling of the stem and petiole. Root growth may be inhibited and the roots may become stubby. Fruit symptoms range from the development of excessively large or small irregular-shaped fruit to the development of flat or nippled blossom-ends or internal deformations. Insecticides typically cause a leaf margin necrosis or necrotic lesions on the foliage.

Generally, foliar damage occurs when the herbicides and insecticides are applied at excessive rates, at the wrong stage of plant growth or during unfavorable weather conditions. Damage often occurs from herbicide drift when crops or weeds adjacent to the tomatoes have been sprayed. Damage from drift is usually most severe at the edge of the field closest to where the herbicide was applied, with the damage decreasing with increasing distance from the source.

Use herbicides and insecticides as directed and apply during the appropriate weather conditions.