1<)0 expp:riment station record. 



DISEASES OF PLANTS. 



Report of the botanists. <;. K. Stonic and R. 1']. SMirii ( Miisr.nclnixi-tlx Sta. li/il. 

 ]90..', }yp. J7--i<s'). — A review is ifivcn of tiie plant disea.ses under nhservation during 

 the .season of 1902 and discu.ssion.s given of some of the more inij)ortant ones. Among 

 the diseases more extensively described are the encumber mildew ( I'hu^mopimt ruhen- 

 sin), nuiskmelon blight, a})j)le leaf spot due to frost injury, a strawberry disease, plum 

 yellows, etc. 



The cucumber mildew, which Avas lirst reported at the ^ra.«sachusetts Station in 

 1889, has since become very ])revalent throughout the Southern and Middle States, 

 and since 1900 has reai)peared in ^Massachusetts, being found on greenhouse cucum- 

 bers in different loctalities. Experiments in spraying for the prevention of this tlisease 

 have shown but little gain attributed to the use of fungicides. When occurring in 

 fields the fungus does not seem to seriously diminish the yield, V)ut when appearing 

 ujion greenhouse cucumbers great damage may be occasitmed. The disease is more 

 ])revalent upon the early started plants, an<l on this account 'the authors reconmiend 

 starting the jilants in October ami keeping the atmospliere of the house in as dry 

 condition as possible. By the removal of the affected leaves the disease may be kej)t 

 in check and where an early crop has been planted si)raying with Bordeaux mixture 

 is recommentled. 



The chief injury to umskmelons reported was from the downy mil<lew which 

 occurred in connection witli the anthracno.se and an Alternaria disea.se. On acccmnt 

 of the serious outbreak of the mildew tlie growing of nuiskuielons has been almost 

 a coniplete failure. An experiment has been conducted in cooperation with local 

 growers to test the efficiency of spraying for the prevention of this disease. The 

 details of the work and the results of the exj)eriment are reserved for a future 

 publication. 



The apple leaf spot was due to frost injury and resulted in the early defoliation of 

 some of the orchards. Those orchards which were in good condition were less 

 seriously affected than neglected trees grow'n under unfavorable conditions. Xo 

 fungus was ob.served and the spotting of the leaves is attributed to the injury caused 

 by the h)W temjjerature occurring during the earh' part of the sea.son. 



The strawberry disease mentioned appears to be a new one. It was first ol)served 

 in the withering and dying of the fruit stalks, followed by the .^ame effect upon the 

 leaves. An examination of these parts showed no fungus, Imt the roots were found 

 in all cases to Vje in poor condition. Further examination showed a fungus growth 

 present in nearly all roots of affected plants, Init attempts to ol)tain cultures in order 

 to determine definitely the tn-ganisni faile<l, as did attempted inoculation experiments. 



The authors report the occurrence on plums, particularly the Japanese varieties, 

 of a disease very similar to the yellows of the peach. This trouble is characterized 

 by the i)roduction of wiry, yellow shoots, just as in ])eacli yellow's. 



A brief account is given of spraying ejcperiments for the control of the linden leaf 

 spot ( Crrcospord ndcrosora) and elm leaf spot {DotlddeUa iihiwa). These trees were 

 sprayed with Bordeaux mixture. The si)rayed trees retained their foliage much 

 longer than those not so treated. It is estimated that in the case of linden trees 

 sprayed twice during the season a gain of from 2 to 5 per cent in growth and devel- 

 opment would be obtained at an almost insignificant cost. 



A brief accoimt is given of the growing of various crops under tent cloth, Ihe 

 experiment being suggested by the success -attained in growing Sumatra tobacco. 

 Cucumbers, watermelons, tomatoes, etc., were grown under cloth shade and, so far 

 as the vegetative growth and freedom from disease were concerned, the experiment 

 was very successful ; but the plants did not set fruit as well as those grown in the 

 o])en. This was due i>T-obably to a lack of insect visitors. 



Experiments in heating- soils, O. E. Stoxe and R. E. Smith {Mdnfi/irJiiisdts Sta. 

 Rpt. 1902, pp. 38-40). — On account of the widespread interest taken in the problems 



