Diseases & Disorders

Blotchy, uneven mottling and overall decline are stronger clues than a perfectly mirrored nutrient pattern.

Look for raised corky lesions with a distinct yellow halo on leaves, twigs or fruit.

Look for leaf chlorosis and tip/marginal scorch associated with fertilizer-grade urea containing too much biuret.

Look for dieback, misshapen growth and coarse or gummy symptoms on shoots/fruit rather than a simple uniform yellow leaf.

Look for herbicide injury expressed as irregular chlorotic or necrotic leaf areas rather than a tidy nutrient pattern.

Look for distorted, narrow or strap-like new growth with chlorosis after herbicide contact.

Look at the newest leaves: the tissue turns yellow while the veins remain sharply green.

Look at older leaves for yellowing on both sides of the midrib that leaves a green inverted-V or arrowhead area near the base.

Look for a light-green/yellow leaf with a network of greener veins, usually less sharply contrasted than iron deficiency.

Look for broadly uniform pale green-to-yellow foliage, commonly beginning on older leaves.

Look for brown necrotic tips and leaf margins, often with a sharp boundary between healthy and burned tissue.

Look for small, narrow leaves with interveinal yellow mottling and shortened internodes/rosetting.

Look for dark brown necrotic lesions with yellow halos on young leaves and fruit, often with irregular expansion along veins.

Look for dark leaf spots that may enlarge or merge and are often surrounded by yellow tissue.

Look for firm brown leathery fruit decay, often beginning on fruit low in the canopy after wet conditions.

Look for chronic decline with bark symptoms such as gum impregnation, pitting or discoloration in susceptible mandarin/tangelo tissues.

Look for dark fruit lesions that can appear as hard spots, freckles or larger necrotic areas, often with contrasting orange/yellow tissue.

Look for an established tree with thinning canopy, wilt, twig dieback and chronic decline despite apparently adequate soil moisture.

Look for asymmetrical blotchy mottling that does not mirror across the leaf midrib; fruit may be lopsided or unevenly colored.

Look for raised corky, wart-like lesions that distort young leaves and fruit.

Look for scaling, shelling or cracking bark on susceptible rootstock tissue below the bud union, often with dwarfing.

Look at the trunk base for dark water-soaked bark, gum exudation, cracking and decay near the soil line.

Look for yellowish leaf spots above and dark, greasy-looking raised lesions on the underside of mature leaves.

Look on grapefruit rind for numerous small dark specks or pits that can create a pink-pitted or rind-blotch appearance.

Look for postharvest fruit decay that starts soft/watery and quickly develops white mold followed by blue-green spores.

Look for many tiny raised dark specks that feel like sandpaper; on fruit they may run in tear-stain streaks.

Look for sharply defined translucent or water-soaked-looking patches between veins that later turn tan or necrotic.

Look for orange-brown lesions on flower petals followed by dropped young fruit and persistent enlarged green calyx 'buttons.'

Look for scaling/flaking bark on trunk or scaffold limbs; young leaves may show temporary flecking patterns.

Look for brown decayed feeder roots together with a thinning, yellowing canopy and poor vigor.

Look for a black soot-like coating on leaves or fruit that sits on the surface over insect honeydew.

Look for very soft, watery postharvest fruit decay with a sour odor and pale fungal growth.

Look for decay beginning at the stem/button end and spreading downward through the fruit.

Look for decline or quick decline on susceptible rootstocks; stem pitting and vein symptoms may occur in some hosts.

Look for superficial corky/russet scarring on fruit where leaves or twigs rubbed the rind during growth.