Phtjfophtliora Rot of Tomato 



301 



gled threads embedded in the epidermis of the fruit. This develops 

 rapidly into a dark water-soaked spot, and in a few days may increase 

 to 20 to 30 mm. in diameter. Several spots often occur on the same 

 fruit and later coalesce into one large spot. (Fig. 1, B). As the rot 

 pi"ogresses dark-brown concentric rings or zones are formed in the dis- 

 eased area, giving it the buckeye appearance. (Fig. 1, C). The fungus 



Fiff. 1. Phijtophthora tcrrestris on tomato fiuit. .1. Incipient infection showing 

 the dai-k brown web- or lace-like early stage of the lesion (X3). B. Lesions three to 

 four days older than the lesion in ,1. C. A later stage showing the concentric brown 

 markings in the diseased area. 



does not cause a marked disintegration of the tissues. The host cells 

 are killed, but the tissue involved is firm until a later stage of the dis- 

 ease, by which time saphrophytic bacterial invaders have entered and 

 caused a soft rot of the fruit. 



On mature tomato fruits, the disease causes a premature ripening 

 and decay. No young lesions were observed on ripe fruits, but young 

 lesions were observed on green fruits of all sizes. From these observa- 



