CITEUS DISEASES. 



(ii) 



This form of disease is due to the work of a eominoii fungus Di- 

 plodia natalensis. The fruiting bodies appear in great numbers on 



the surface of the dead liark, as small 

 1)1 ack carbonaceous, slightly i-oughened, 

 hemispherical to flattened ])ycnidia, with 

 in which are borne the reproductive bod- 

 ies or conidia. These latter are distrib- 

 uted by wind, water, and probably in- 

 sects, as well as I)y various insti'unients 

 (Muployed in gi-o^'e work. 



I n attacking 

 the twigs, Diplo- 

 (lia p r o d u c .- s 

 symptoms ver; 

 similar to tlios' 

 of withertip, and 

 in fact till' injury 

 caused has been 

 called Diplod^a 

 withertip, or di''- 

 back. T h e r e is 

 usually a slight 

 production of 

 g u m t o distin- 

 guish this malady 

 from true withertip. In cases where this is 

 not produced the disease may spread back 

 into the larger limbs, or even the trunk, the 

 gum apparently serving to check the growth 

 of the fungus. The presence in advanced 

 stages of the very characteristic fruiting bod- 

 ies also helps to distinguish it from Colleto- 

 IricJnoii. The latter, however, will also gen- 

 erally be present. In addition to the con- 

 trol measures outlined below, the general discussion under witliertip 

 will be applicable. 



Fig. 4. — D i jj 1 o d i a cauker. 

 Showing black fruiting 

 bodies of the fungus on 

 dead grapefruit branch. 



Fig. u. — Diplodia die- 

 back. Note the sharp 

 transition between 

 dead and living tis- 

 sues. 



Control. 



Pruning of all diseased branches or twigs, and cutting out of 

 lesions on the trunk, or main limbs will serve to control the malady 

 if all precautions are taken. Exactly the same steps are necessary 

 as have already been described for other bark diseases, but witli 



