Grape Fruit Physiological Disorders

A Lecture To ToT trainees

( FFS) By

Mr. Allah Dad Khan Provincial Coordinator IPM

KPK MINFAL Pakistan

Frost

Identification tip:  Frost dieback Brown dead leaves remain

attached to trees damaged by cold weather, giving plants a scorched appearance. Certain other leaf and twig diseases and disorderscause similar damage. With cold injury, damage is most prevalent on outer, exposed branches. Young trees are especially susceptible to cold.

Sunburn discoloring

Identification tip:  Exposure to hot sun can kill

parts of leaves and fruit, resulting in yellow-to-brown blotches. Sunburn also causes bark cankers (not shown). Injury is most prevalent on the south and west sides of the tree if sun exposure is the cause of damage.

Fruit Splitting: Identification tip:

  Rinds split at the bottom of fruit after tree stress, such as extreme weather, inappropriate irrigation, and potassium deficiency. Decay fungi such as Alternaria rot or blue and green mold often invade wounded fruit.

Puff and crease

Identification tip:

  An uneven appearance develops on the outer surface of rinds when the outer rind has separated from inner fruit. The apparent cause is different growth rates between the inner fruit (endocarp) and the white layer (albedo) under the peel

Puff and crease

Peteca of lemon

Identification tip:

This lemon malady causes depressions in the rind, which become discolored or brownish

Rind disorder

Identification tip:  Brown, water-soaked

blotches or dark, sunken areas develop on the rind after rainy weather and as fruit matures and turns orange. Secondary fungi may colonize affected areas as the fruit breaks down. This physiological problem (abiotic disorder) is a problem in California on Satsuma mandarins.

Hail damage

Identification tip: 

Hail impact causes discolored scars on fruit and twigs and tears or shreds leaves. Damage occurs on the exposed side of fruit, including locations not likely to have been impacted by equipment.

Wind scarring

Identification tip: During persistent winds, fruit may rub against twigs or thorns and develop scars.

Shallow, discolored scars on the rind occur when fruit rub against twigs or thorns, especially on lemon trees at exposed locations

Chimera

Identification tip: 

A raised section in fruit, typically in a wedge-shape, is usually from  chimera. This genetic mutation is of minor importance.

Fruit Drop

Summer Drop During the late spring and

early summer, most citrus trees will naturally drop tiny, marble-sized fruit. Citrus trees lose some of the developing fruits to prevent the tree from being weighed down by an excessive amount of ripening fruit. Unless your citrus tree has another problem and you are losing fruit in May, June or July, the cause is likely natural and unavoidable..

Pruning

Symptoms Too much pruning may cause a

loss of young fruit from your tree. Citrus trees rarely need heavy pruning. For the best results from your tree, prune it to remove branches that are dead, diseased, decaying or in danger of harming other branches by contact. The best time to prune is after the last frost in the spring or during the summer before August, to prevent cold damage on any new growth that appears after pruning.

Drought Stress

Symptoms Inadequate watering of a

citrus tree tends to put the tree under stress. A drought-stressed tree may jettison its fruit to ensure the survival of the food-making leaves, branches and remaining fruit. Make sure the tree is well watered. Mulch around the base of the tree to help conserve water in the soil.

Temperature Changes

Symptoms Sudden, drastic temperature

swings, especially right after fruit set, could cause the tree to drop immature fruit. High temperatures helps to sweeten citrus fruit, but they should be later in the summer, after the young fruit has begun to grow. During periods of high heat, you will also need to pay attention to the amount and frequency of watering. If the citrus trees are in pots, they may need daily watering during warm weather.

leocellosis:

leocellosis::  It is caused by rind oil release when

oil cells get ruptured during harvesting or during handling from the field to the pack house. It is more common in crop taken in 'Mrig' bahar and harvested during February- March. Careful harvesting and handling reduces incidence of oleocellosis. Rind oil from ruptured cells discolours the skin making the fruit unmarketable.

Control : Best way to reduce its incidence is to cure the fruit overnight at a temperature of 18-20 C for 12-24 hrs, before the fruit is moved from the field to the pack house

Nutrient Disorders

Identification tip: Iron deficiency symptoms on young citrus leaves.

 Leaf discoloring occurs between distinctly greener veins when nutrient disorders such as a deficiency of iron (shown here), potassium, or zinc are the cause

Nitrogen deficiency

Identification tip:

 Foliage is pale overall when nitrogen is deficient. The causes include a true deficiency of nitrogen, adverse soil conditions, or unhealthy roots

Phosphorus Deficiency

SymptomsFigure 4.  Phosphorus deficiency[Click thumbnail to enlarge.]

Fruit are rather coarse with thick rinds (Fig. 4) and have lower juice content which is higher in acid. Although rarely observed, foliage may exhibit a bronze appearance. Phosphorus deficiency is unlikely to occur in groves that have received regular P applications in the past. However, new plantings on previously uncropped land usually require substantial initial phosphorus applications

Potassium Deficiency

Symptoms Figure 5.  Potassium deficiency (3 levels of K deficiency with the smallest fruit being the most deficient.)

Fruit are smaller, have smoother, thinner rinds and may be subject to splitting and/or drop (Fig. 5). Potassium deficiency is likely to occur on calcareous soils due to elemental antagonism, and where large crops of fruit are produced with high nitrogen rates. A rarely observed bronzing of foliage may sometimes be observed, particularly on lemons.

Manganese Deficiency

Symptoms Figure 7.  Manganese deficiency

Deficiency appears as dark green bands along the midrib and main veins surrounded by light green interveinal areas giving a mottled appearance (Fig. 7). As severity increases, the light green interveinal areas give way to a yellow-bronze coloration. Both manganese and zinc deficiencies may occur on calcareous soil and may be more severe on trees with highly pH-sensitive rootstocks. Incipient manganese symptoms may sometimes disappear as the season progresses, so leaves should be observed several times before remedial action is taken. Soil and foliar applications may be effective in correction of manganese deficiency

Role of Soil pH

Symptoms Lemon trees perform best in a soil with a pH

level more acidic than many plants require, between 5.5 and 6.2. Yellowing among the veins on a leaf that signals an iron deficiency may not arise because the soil lacks iron. The true reason might be that the soil tends toward the alkaline side and cannot put the iron into a usable form for the plant. A home soil test or a test sent to a soil-testing laboratory will report your soil's current pH level. If the soil tests too high for a lemon's acidic preference, add elemental sulfur. To lower the pH by one point, for example, from 6.5 to 5.5, use 2 1/2 pounds per 100 square feet in loamy soil. If your soil is sandy, reduce the application by one-third. For clays, increase the amount of sulfur added by 50 percent. Work it thoroughly into the top 6 inches of the soil.

Sunscald

Foliage Symptoms

Symptoms

Since similar symptoms, such as yellowing of leaves, can indicate too little of a number of different nutrients or micronutrients, you should submit or take a take home soil test before supplementing. Insufficient water contributes to nutrient deficiencies, as can soil pH imbalance. Nitrogen inadequacy, the most common deficiency, results in foliage turning yellow from the lower leaves up. Iron, manganese and zinc deficiencies often appear together as lighter splotches between the veins of a leaf. If this abnormality only shows up on the south side of the tree, it may signal a shortage of zinc. Occurring on the north side, a manganese deficiency is the likeliest culprit. In overwatered, poorly drained soil, yellow splotches probably indicate that the tree does not receive enough iron. A symptom of magnesium deficiency is a yellow spot that begins at a leaf's base and gradually spreads over most of its surface.

Zinc Deficiency

Symptoms Figure 8. Zinc deficiency

Early stages appear as small blotches of yellow between green veins on the leaf. With severe deficiency, leaves may become increasingly yellow except for the green veinal areas (Fig. 8). Under severe deficiency conditions, leaves will also be small with narrow pointed tips on terminal growth. Foliar fertilizer applications are usually recommended for correcting zinc deficiency. Trees with citrus blight will also show leaf symptoms of zinc deficiency.

Iron Deficiency

Symptoms Figure 9. Iron deficiency

In mild cases, leaf veins are slightly darker green than interveinal areas with symptoms appearing first on new foliage (Fig. 9). In severe cases, interveinal areas become increasingly yellow with entire area eventually becoming ivory in color with emerging foliage, which is smaller. Trees may become partially defoliated with eventual twig and canopy dieback. Iron deficiency is usually an indication of calcareous soil condition and is more likely to be expressed on high pH-sensitive rootstocks like Swingle citrumelo. An early expression of flooding damage to roots and of copper toxicity may be iron deficiency symptoms.

Copper Deficiency

Symptoms Figure 10. Copper deficiency (ammoniation)

Mild copper deficiency is usually associated with large, dark green leaves on long soft angular shoots. Young shoots may develop into branches which appear curved or “S-shaped," referred to as “ammoniation” usually resulting from excessive nitrogen fertilization (Fig. 10). Twigs can develop blister-like pockets of clear gum at nodes (Fig. 11). As twigs mature, reddish brown eruptions may occur in the outer portion of the wood. Severely affected twigs commonly die back from the tip with new growth appearing as multiple buds or “witches broom”. Necrotic-corky areas on the fruit surface may sometimes occur in extreme situations. Copper deficiency is more likely to occur in new plantings on previously uncropped soils, which are usually deficient or totally lacking in copper

Boron Deficiency

Symptoms Figure 12.  Boron deficiency

Fruit symptoms most indicative of boron deficiency include darkish-colored spots in the white albedo of fruit and sometimes in the central core (Fig. 12). Fruit may be somewhat misshapen with a lumpy surface. Unlike other micronutrient deficiencies, boron can impact fruit quality and should therefore not be allowed to occur. Slight excess can cause toxicity, so maintenance or correctional applications should involve ground or foliage applications, but not both.

Molybdenum Deficiency

Symptoms Figure 14.  Molybdenum deficiency

Rarely observed, it can occur under acidic soil conditions. The most characteristic field symptoms are large yellow spots on the leaves that appear first as less defined water-soaked areas in spring (Fig. 14), later developing into distinct larger interveinal yellow spots.

Phytotoxicity from diuron

Identification tip:  When citrus roots take up too much diuron, major leaf veins turn yellow

Leaf veins can turn yellow or white (vein clearing) after herbicide application due to citrus root uptake of bromacil or diuron. After simazine exposure, leaves yellow between veins with the chlorosis increasing in severity in proportion to the amount of herbicide exposure.

Phytotoxicity from simazine

Identification tip:  Range of damage from simazine on citrus

Pale blotches develop in leaves after exposure to simazine herbicide. Interveinal chlorosis can range from relatively mild to severe depending on the amount of herbicide absorbed.

Mesophyll collapse

Identification tip:  Mesophyll collapse of leaves caused by water stress.

Soft tissue between leaf veins becomes sunken and translucent or pale due to moisture stress when trees are unable to provide leaves with enough water; affected leaf tissue then becomes tan-colored or necrotic.

Salt Injury

Symptoms Figure 16. Salt injury Many salinity-induced symptoms are similar

to drought stress symptoms, including reduced root growth, decreased flowering, smaller leaf size, and impaired shoot growth. These can occur prior to more easily observed ion toxicity symptoms on foliage. Chloride toxicity, consisting of burned necrotic or dry appearing edges of leaves, is one of the most common visible salt injury symptoms. Actual sodium toxicity symptoms can seldom be identified, but may be associated with the overall leaf “bronzing” (Fig. 16) and leaf drop characteristic of salt injury. Slightly different symptomology may occur depending on whether injury is due to root uptake or foliage contact. Excessive fertilizer applications, highly saline irrigation water, and storm-driven ocean sprays can all result in salinity-induced phytotoxic symptoms.