A2606 omato disorders: Early blight and Septoria leaf spot T KAREN DELAHAUT a n d WALT STEVENSON Both early blight and Septoria Symptoms and effects Septoria leaf spot is first notice- leaf spot are potentially serious dis- Early blight is primarily a able by the small, circular spots on eases that affect the leaves, stems, foliage disease, but may also cause the upper surface of the lower leaves. and fruit of tomatoes. Early blight, fruit to rot near the stem in late fall. There is often a corresponding water- caused by the solani, Symptoms of early blight first appear soaked spot on the lower leaf surface. can also infect . Septoria leaf on older leaves and are characterized These spots are smaller and more spot is caused by Septoria lycopersici by irregularly shaped brown spots numerous than those of early blight. and can infect ground cherries, jim- with concentric rings. Usually the They are 1/16–1/4 inch in diameter sonweed, and nightshade as well. tissue surrounding each spot turns and have a tan or light-colored center. Both diseases thrive during periods yellow. The spots enlarge to Tiny black fruiting bodies may be of moderate temperatures and abun- 1/4–1/2 inch in diameter and coalesce, found in the center of these lesions. dant rainfall. They may occur on causing the leaf to turn brown and Infected leaves may drop from the plants of any age, but they usually drop. As the plant loses its leaves, the plant. Spotting of the stem and blos- become evident after the plants begin fruit become exposed to the sun and soms may also occur. to set fruit. susceptible to sunscald. Infected fruit Both diseases can be identified have dark, leathery, sunken spots with reasonable accuracy in the field. near the stem end. Only green fruit Laboratory examination, if necessary, are infected. will confirm the field diagnosis. For more information about submitting a specimen, consult your county Extension office.

Early blight on tomato. Note the yellow halos surrounding large, irregularly shaped lesions.

Early blight Septoria leaf spot

To identify the diseases in the field, look at the size and shape of the spots: Large, irregular spots and yellowing leaves are indicative of early blight; Septoria leaf spot causes small, round spots with light centers. TOMATO DISORDERS: EARLY BLIGHT AND SEPTORIA LEAF SPOT

Disease cycle Staking or caging plants also helps It may be necessary to treat The early blight pathogen over- speed drying of plants after wetting tomatoes with protectant fungicides winters on infected plant debris and keeps fruit and leaves off the soil. to control Septoria and early blight. where it can survive for 1 year, on Do not water late in the day unless Begin treatment when the first fruit seed, or in the soil. Septoria can you are using trickle irrigation. Mulch clusters start to develop or when the survive for up to 3 years in infested will act as a barrier between the soil first symptoms are observed. Some debris, but it can also survive on and foliage to prevent spores from growers find that a few well-timed weedy hosts such as jimsonweed, splashing onto the leaves and fruit. sprays control the diseases while horsenettle, groundcherry, and night- Carefully monitor plants weekly other growers treat more frequently shade. Initial infection occurs on the once they begin to flower for early and still find that control is difficult. lower leaves and spreads upward symptoms of these diseases. Pruning Applications of fungicide may be in the plant as spores from infected and destroying the lowest leaves will needed every 7–10 days when the leaves are splashed onto clean foliage improve air circulation and hasten weather is wet and warm. Observe by rain or irrigation water. Spores can drying of the foliage after wetting. the new foliage regularly to be sure also be spread if field work occurs Removing leaves at the first sign that the sprays are effective. while plants are wet. of infection will also help slow the spread of the disease. Control At the end of the season remove Rotate out of solanaceous or thoroughly incorporate all crop (tomato family) crops for 3–4 years refuse. If the remains are buried and control solanaceous weeds such deeply and decay, the fungi have as jimsonweed, horsenettle, ground- less chance of overwintering. Do cherry, and nightshade to reduce the not compost infected vines unless build up of spores of both diseases you practice stringent composting in the soil. Use disease-free seed and practices that will assure prolonged inspect purchased transplants for leaf heating to kill the disease organisms. spots before transplanting into the There are presently no tomato field. varieties resistant to Septoria leaf Select a well-drained site with spot. A few tomato varieties are good exposure to the sun and wind reported to be tolerant to early blight, to promote drying of the foliage after but they have not proven to perform rain or dew. Space plants far enough well in Wisconsin. apart to allow good air movement.

Copyright © 2004 by the Board of Regents of the University of Wisconsin System doing business as the division of Cooperative Extension of the University of Wisconsin-Extension. All rights reserved. Send copyright inquiries to: Manager, Cooperative Extension Publishing, 432 N. Lake St., Rm. 103, Madison, WI 53706. Authors: Karen Delahaut is senior outreach specialist with the fresh market vegetable program, Walt Stevenson is professor of , College of Agricultural and Life Sciences, University of Wisconsin-Madison and University of Wisconsin- Extension, Cooperative Extension. Produced by Cooperative Extension Publications, University of Wisconsin-Extension. University of Wisconsin-Extension, Cooperative Extension, an EEO/AA employer, provides equal opportunities in employment and programming, including Title IX and American with Disabilities (ADA) requirements. This publication is available from your Wisconsin county Extension office or from Cooperative Extension Publishing. To order, call toll-free: 1-877-947-7827 (WIS-PUBS ) or visit our web site: cecommerce.uwex.edu.

A2606 Tomato Disorders: Early Blight and Septoria Leaf Spot R-05-04