[Illustration: Figure 1. Scab lesions on leaves and nuts of Delmas variety. Note concave lesions and overall scabby appearance of severely infected nuts.] [Illustration: Figure 1. Infected nuts.] Pecan varieties vary in their susceptibility to scab disease. Among the highly susceptible varieties are: Burkett, Delmas, Schley, Moore, Halbert and most western varieties. Moneymaker, Success and Curtis are moderately resistant. Mahan, Stuart and Desirable varieties are highly resistant to the scab fungus. However, this character of resistance varies, depending on the area of the state, local environmental conditions and the particular strain of the scab fungus present. Scab disease development is favored by rainy periods and cloudy days when the humidity remains high and leaf surfaces are wet. Under these conditions, spores of the fungus in contact with the wet leaf surface of a pecan leaflet or nut germinate rapidly, invade the tender tissues and initiate infection within 6 hours. Lesions resulting from these infection sites, become visible to the naked eye within 7 to 14 days, depending on environmental conditions. A period of warm dry weather after infection occurs may retard lesion development. _Control._—The control of pecan scab disease depends primarily on the protection of tender leaf, nut and shoot surfaces with proper application of an effective fungicide. A protective film of fungicide chemical prevents scab fungus infections by killing the spores immediately after their germination, thereby preventing invasion of susceptible tissues. Unfortunately, once the fungus has invaded the tissues it becomes protected from chemical attack and produces spores in great abundance. Therefore, thorough coverage of leaf, nut and shoot surfaces with a fungicide chemical must be maintained to prevent secondary infections, ([6], [10], [11]). Sanitation measures, such as removal of old attached shucks and leaf stems in trees and plowing or disk harrowing under fallen leaves and shucks help reduce primary infections. See spray schedule, page 4, for scab disease control. BROWN LEAF SPOT The brown leaf spot disease fungus _Cercospora fusca_ (Heald and Walf) Rand affects only mature leaves and usually does not appear until the latter part of May or mid-June. Primary lesions develop on the lower leaf surfaces as small dots, which gradually enlarge and become reddish brown with a grayish cast. The shape of the lesions may be circular or irregular, especially where two or more lesions develop adjacent to one another, Figure 2. In seasons favorable for brown leaf spot development pecan trees may be completely defoliated within 3 to 4 months if the disease is not controlled. Most pecan varieties which are maintained in a vigorous state of growth are resistant to brown spot disease. _Control._—See spray schedule, page 4. VEIN SPOT