Diagnosing Leaf Injury Symptoms 



Karen I. Hauschild 



University of Massachusetts, West Springfield, MA 



Growers often are faced with individual trees or 

 gi'oups of trees that show unusual leaf symptoms -- 

 either color changes, shape or size differences, or in 

 some situations, leaves "just don't look right." It is 

 relatively easy to rule out insect and disease problems, 

 but often it is much more difficult to diagnose nutri- 

 tional or weather- related foliar damage. The purpose 

 of this aiticle is to help gi'owers determine the cause of 

 non-pest related foliar damage. 



Herbicide injuiy is often confused with, or hard to 

 distinguish from, nutritional deficiency symptoms. 

 The best clue to herbicide injuiy is your knowledge of 

 application - how and when each herbicide was ap- 

 plied. Proper sprayer calibration, attention to label 

 directions, and attention to weather conditions when 

 applying materials all will help to minimize herbicide 

 damage. 



Common Herbicide Injuries and 

 Their Symptoms 



Terbicil (Sinbar^*^) -- Injury results in pronounced 

 differentiation of green and yellow areas of leaves. 

 Leaves also may appear deformed. Leaf veins may be 

 greener than normal. 



Dichlobenil (Casoron^"^) - Injuiy results in yellow- 

 ing of the leaf margins. Leaves may be deformed. 



Diuron (Karmex^*^) - Injury is similar to calcium 

 chloride injury and moisture stress. It is characterized 

 by browning of leaf margins that eventually progi-esses 

 throughout the leaf. 



Simazine (Princep^") - Injury develops as necrosis of 

 the leaf margins, wdth a quick onset of necrosis of the 

 entireleaf. Leaves also may appear blotchy. With more 

 severe damage, leaves tear and veins become more 

 pronounced. 



Weather-related Injuries 



Drought - Symptoms originate at leaf tips, and mar- 

 gins then become necrotic. These symptoms usually 

 follow a period of dry weather. 



Frost injury - Injury shows as a whitening of leaves. 

 Leaves become parchment-like in appearance. Symp- 

 toms are often confined to lower limbs. 



Nutritional Deficiency Symptoms 



Nitrogen (N) - The primaiy expression of deficiency 

 is the yellowing of leaves. Leaves also may be tinged 

 with red and the coloration may progi-ess to orange-red 

 with time. Leaves also can be small and deformed and 

 may abscise. 



Potassium (K) - Deficiency is most often a problem 

 on young, fruiting trees. It starts as a loss of green color 

 followed by a water-soaked appearance in the older 

 leaves and progresses to leaf scorch. 



Magnesium (Mg) - Older leaves are affected first. 

 Areas between leaf veins become yellow, and with time 

 become necrotic. By late summer, shoots may defoli- 

 ate, leaving tufts of green leaves at tips. 



Manganese (Mn) - Deficiency appears first on older 

 leaves and is seen as fading of leaf margins. This fading 

 is inward progi-essing toward the leaf midrib. Green 

 veins may be sharply defined with white-yellow colora- 

 tion between them. 



Zinc (Zn) - Deficiency may appear as rosettes of leaves 

 in early spring (dense cluster of narrow leaves above, or 

 at the end of, an othei-wise leafless twig). It also may 

 show as short, lateral spurs, or marginal intei-veinal 

 yellowing. 



Although it often is difficult to diagnose the cause 

 of leaf injuries, knowledge of local weather patterns 

 and accurate, up-to-date herbicide and fertilizer appli- 

 cation records will help you make an accurate diagno- 

 sis. Where one or more nutritional deficiencies is 

 suspected, foliar tissue analysis can confirm your diag- 

 nosis. When leaf symptoms occur, the above symptom 

 descriptions should help you determine the tree's par- 

 ticular problem. Remember, however, that more than 

 one problem could be present, and that often one 

 symptom can mask another. 



•i» ai* «£a «{• •!« 



•J» »J» •J* ^g» Bj* 



12 



Fruit Notes, Spring, 1989 



