TH E AG RICU LTl • 1 1 \ I . N E W - 



February 13, 191-">. 



FUNGUS NOTES. 



MORE ABOUT CITRUS CANKER. 



The Florida Agricultural Experiment Station 



I lletin l_i. H4, three papers 



on the iiiw citrus disease, wl iummarizcd below. 



I. HISTORY OJ CITRUS I WM.l:. E. W. BERG i 



The realization thai a new citrus disease was presenl in 

 Florida lace in Jul} 1913, when it was found in 



oursery. Specimens 

 bad been reci i I pear earlier, but 



apposed al th tt time to sh >w merely an um 



The infections were traced partly to 

 imporl ■ m Texas, parti} to stock 



I i from Japan. Il transp that the 

 disease was present in Alabama, Mississippi, and L* 



An order was issued prohibiting importations of citrus 

 plants into Florida; a fund was raised to which the Florida 

 Growers' and Shippers' Association contributed $2,000, 

 unci the Governor of Florida §1,000; and a campaign was 

 started against the disease. 



II STUDIES OF CITRt s I INKER, n. E. 3 n-:\ ENS. 



Grapefruit is most severely attacked, the infection 

 ing 'hi leaves, twigs, branches and fruits; then in order 

 of susi ptibili trifoliata, and the navel and 



some of thi ■ ■• i : ' ies, \\ hich are affected on 



twigs, and fruit Scattered infections bave been 

 found on the leaves and twigs of Satsuma, tangerine, lime, 

 and rough lemon. 



'The distinguishing feature of citi r, as observed 



in the field, is the characteristic spotting produced on the 



fruit and foliage. As usually seen, the infectio 



as small light-brown spots, from less than -fa to | i 



in diameter. The spots are usuall} round, and maj 



occur singly, or several may run together, forming an 



irregular are;.. This last usually occurs on fruits. The 



spots project above the surrounding healthy tissue, and are 



composed of a spongy mass of dead cells covered by a thin 



white or greyish membrane. The membrane finally ruptures 



and turns outward, forming a lacerated or ragged margin 



and the spot. 



'On the leaves, infections first appear as small, watery 



dots, with raised convex surface These dots are usually of 



i darkei green than the surrounding tissue. Sometimes, 



however, the surface of the spots' is broken as soon as the} 



appear. Spots may appear on either surface of the leaf, but 



it ;ii first penetrate through the leaf tissue. They 



in a light brown, and 



■ visible on both sides of the leaf. In the oldet 



both surfaces may be bulged or raised, and such spots 



iinmonlj A irrow yellowish hand or 



In the • adva bh< the spots 



becomes white or greyish, a ruptures, exposing 



.i light brown spongy central mas Old spots soon become 



ovi a by saprophyl ii < > md ma} appeal pink or 



ro v ths 

 •( ii i lie i ruit s, the very similar to those formed 



i.ii the i i They project and retain a circular outline. 



The} do not | I be rind The} may be 



scattered over eyeral ma} occut toj 



forming an irregular ma is sometimes asso- 



.i'Ii the pots formed o tin fruits. < anker, appar 

 < nth. i fruits directly, but 



I ca tits' to 



rot. Tip i young twigs are like those on the leaves 



and fruit. On the older twigs they are more prominent, 

 and more ot less i regular in shape. This is especially true 

 • I old spots. The> show tie tissue as is found 



in the spots on the feaves, but assume i cankerous appear 



mbrane completely disappe 

 The formed in 1 1 layers of the 



bark tissue, and d trate to or kill the wood. The 



spots once fornn and not 



readibj I mghed off. Th :, and 



Qtres fr which infections ma} readily spread. This 



is confirmed 1 i | luced on pot ted 



trees in the greenhouse, and tnth s;ro i byartificial in 



So) i I ider o >n foi 



over a yeat , and show no h off. 



•( (ther citrus di leases n il h ■■■ , confused 



are Seal., Scaly hark, and possibl} Anthracnose. It can, 

 however, readih ' distinguished from any of tl oting 



the following point s; 



'1. It differ; ft >m scab in the typical round spots pro- 

 duced; the size of the spots, and the fact that the spots 

 penetrate through the leaf tissue. It does not distort the 



leaves. There are no wart-like projections. Canker occurs 



Ider wood, Si al does not. 



'2. Canker differs, from Seal} Bark in the size of the 

 spots, which are much smaller and mure circular than those 



of Scaly Bark; and the sj gy nature of the spots Scaly 



hark spots are h ml and glazed. < tanker is e. minion on grape 

 fruit, Seal} Bark is not. Canker forms spots on leaves, 

 Scaly Hark does not. 



'.'?. Canker differs material!} from Anthracnose in the size 

 of the spots, which are much smaller than those of Anthracnose. 

 Canker spots are raised, Anthracnose spots are sunken. 

 Canker has spots ol pong} character, those of Anthracnose 



hard. Canker occurs on young shoots and older twig 

 Anthracnose does Qol 



periments in which dry infected material was pinned 

 to } Lth} foliage showed that the disease was infec- 



tious. Small watery spots appeared in one month, and th 

 had developed in two months into the spots typical ol the 

 disease A fungus was isolated from the young spots, and 

 afterwards identified an| present on the older spots. 



Infection experiments from ] dtures gave positive results 



in two out of many instan 



The fruiting bodies of the fungus are small globular 

 pyenidia, which exude the colourless spores in thread-like 



tendrils. The pyenidia are - ivhal difficult to distinguish 



from the tissues of the spots. 



The disease spreads with great rapidit} in rainy weather: 

 infection proceeds from the old spots even after these have 



d through a winter. 



111. ERADH \ I i"\ of CITRUS ' INKER, FRANK STIRLING 



Mr. Stirling was employed b} the Growers League to 



try 1. 1 clear up the disease first of all in Dade County, a 

 district in which the grape fruit industry is developing very 

 rapidly. He tells his stor} very dramatically. 



At the outset some 200,000 nursery trees and over 50Q 

 acres of grove tree- were cut hack, defoliated, and the trunks 

 painted with Bordeaux mixture or carbolineum. 'At this 

 juncl i to breathe a littli easier. A- the 



inspection proceeded, more and more infection ».i~ found, and 

 more and more was treated. The number of infected proper- 

 tips rose to nearl} i hundred Tien with the new growth 

 ..ii the trees came the -hock of finding that the work had h 

 carried bul in vain ; that instead the 



activity of the worl I ! .\ contributed to its spread, 



