Diuron Injury: A faint loss of chlorophyll from the main veins is 

 the first distinguishing characteristic of diuron injury to EM VII 

 rootstocks. As the condition worsens, the interveinal areas adja- 

 cent to the main vein become yellowish-green, being most severe on 

 the basal portion of the leaf. The fading of chlorophyll (chloro- 

 sis) in the affected area results in a striking contrast in colora- 

 tion since the remainder of the leaf remains dark green. The leaves 

 on the lower branches are affected first. Chlorosis is followed by 

 marginal browning (necrosis) of the leaves. Severe injury causes 

 interveinal necrosis and abscission. 



Paraquat injury : Injury from 

 paraquat results when tree fol- 

 iage or fruit is hit by spray; 

 injury does not result from 

 root absorption. Varying de- 

 grees of chlorosis and necrot- 

 ic spotting occur on apple fol- 

 iage with no distinctive pat- 

 tern. The older chlorotic tis- 

 sue breaks down and necrotic 

 spots appear. Abscission of 

 severely injured leaves occurs. 

 The skin of young apple fruits 

 hit by paraquat spray may show 

 burn spots or russet. The skin 

 and flesh in the severely 

 burned areas cracks (Figure 1) 

 and many badly injured fruits 

 drop prematurely. 



,*«# 



:^^ 



Fig. 1 



Dal apon i njury : The dis- 

 tinguishing symptom of dala- 

 pon injury is marginal leaf 

 necrosis (Figure 2.) Dala- 

 pon is readily translocated 

 in the plant and new growth 

 following spraying may devel- 

 op severe injury symptoms. Dalapon 

 sist through the growing season. 



Injury to Mcintosh apple from 

 paraquat spray. Skin and 

 flesh of areas burned by para- 

 quat cracked and then healed. 



injury has the tendency to per- 



Dichlobenil injury : Symptoms of dichlobenil injury are characterized 

 by yellowing of the leaf margin (Figure 3), which generally appears 

 in early August or later and persists throughout the growing season. 

 The injury is found on spur leaves and/or current season growth, 

 and on terminal growth the basal leaves are the first to be affected. 

 In case of slight injury, only a few of the serrations on a leaf 

 will be yellowed. More severe damage may be expressed by interveinal 

 yellowing extending from leaf margins. Late in the season, necrotic 

 areas develop on the leaf margins and the margins may become tattered 



Several researchers have reported that fruit trees are quite tol- 

 erant to dichlobenil and it has been used successfully in nurseries 



