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Septoria Leaf Spot

Septoria Leaf Spot

Septoria lycopersici

fungi

In a Nutshell

    Small grey circular spots with dark-brown margins appear on the undersides of older leavesBlack dots appear in their centersLeaves turn slightly yellow, wither, and fall off

Hosts: %1$s

· Tomato

Symptoms

Symptoms spread upwards from oldest to youngest growth. Small, water-soaked grey circular spots with dark-brown margins appear on the undersides of older leaves. At later stages of the disease, the spots enlarge and coalesce, and black dots appear in their centers. The same pattern may also be observed on stems and blossoms, but rarely on fruit. Heavily infected leaves will turn slightly yellow, wither, and fall off. The defoliation leads to sun scalding of fruit.

Trigger

Septoria leaf spot occurs worldwide and is caused by the fungus Septoria lycopersici. The fungus infects only plants of the family of potato and tomato. The temperature range for the development of the fungus varies between 15° and 27°C, with optimal growth at 25°C. Spores might be spread by overhead water, splashing rain, hands and clothing of pickers, insects such as beetles, and cultivation equipment. It overwinters on solanaceous weeds and for short periods in soils or soil debris.

Biological Control

Copper-based fungicides, such as Bordeaux mixture, copper hydroxide, copper sulfate, or copper oxychloride sulfate might help control the pathogen.

Chemical Control

Always consider an integrated approach with preventive measures together with biological treatments if available. Fungicides containing maneb, mancozeb, chlorothalonil, and benomyl effectively control Septoria leaf spot.

Preventive Measures

    Acquire certified disease-free seedsIf available, use resistant varietiesRemove infected leaves and destroy themImprove air circulation with stakeKeep plants off the groundRotate with non-solanaceous plantsMake sure that production areas are free of susceptible weedsApply organic or plastic mulch to avoid transmission from soilDo not use sprinklers or other overhead irrigationKeep your equipment and tools cleanRemove or destroy plant debris by deep plowing immediately after harvest