http://uvalde.tamu.edu/STAFF/Black/PDNCR06Text.htm#SEED_AND_SEEDLING_DISEASES

Abiotic Stress

Ozone

Temporary high concentrations of ozone can cause "atmospheric scorch" on peanut leaflets. Nitrogen dioxide and hydrocarbons emitted from automobiles, industrial combustion, oil refineries and other sources react with sunlight to form ozone. Lightning during electrical storms produces ozone which can damage the surface of peanut leaflets. A scorched area appears primarily on the upper leaf surface of the youngest peanut leaflets. Pepper spot caused by a species of the fungus Leptosphaerulina may develop in these scorched leaves. Regular use of a foliar fungicide helps minimize injury by this weak pathogen in damaged tissue.

Salts

Low peanut yields, marginal leaflet burn, and severe pod rots are potential problems in soils with a high sodium adsorption ratio (SAR). The foliar symptoms that develop after irrigation with saline irrigation water vary from a brown marginal leaflet burn to death of the leaflet. Pod rot often increases when sodium (Na), potassium (K), and perhaps other cations accumulate in soil in the fruiting zone. Excess cations compete with calcium for position on soil particles and allow the Ca to move below the pod zone. Calcium is a nutrient absorbed in large quantities by the developing pods and essential for high kernel quality. Calcium deficiency in pods may be associated with increased susceptibility to pod rot fungi. Supplements of gypsum (land plaster) can decrease pod rot under high SAR conditions. Water infiltration into soil is decreased in soils with high SAR. Furrow diking can reduce runoff after rainfall and irrigation and increase flushing of sodium from soil.

Boron

Boron is required in very small amounts for peanut kernel quality. However, toxicity is a problem in some soils in West Texas, decreasing plant growth and yields. Yield decrease occurs with few foliar symptoms (reduced canopy size). Soil and irrigation water should be tested at least annually in areas at risk for high Boron. Test results should be considered when selecting fields for planting.

Alkalinity

Alkaline (high pH) soils are a challenge for optimal peanut production. Canopy symptoms may include yellowing and reduced leaflet and canopy size. Supplementation may be necessary for minor elements that are less available at high pH. Nodulation and nodule activity should be monitored because some fields may need Bradyrhizobium inoculant every time peanut is planted. Nitrogen fertilizer may be needed if nodule numbers and activity are not high.