August 29, 1908 



HORTICULTURE 



281 



The Chestnut Disease 



The disease affecting the chestnut trees, first noted 

 about New York State two or three years ago by Dr. 

 \V. A. Murrill of the New York Botanical Gardens, has 

 become a very serious one in that locality. Dr. Murrill 

 has studied this disease and published the results in 

 various numbers of the Journal of the New York Bo- 

 tanical Gardens, and finds associated with it a fungus 

 which he has named Diaporthe parasitica, Murr. He 

 carried on some inoculation experiments showing that 

 this fungus is capable of producing the disease when 

 inoculated into healthy trees. The recent reports con- 

 cerning the disease seem to indicate that it is spread- 

 ing widely and rapidly, and mention is made of its oc- 

 currence in southern Connecticut in 1907 by Dr. G. P. 

 Clinton. 



Those who are well acquainted with the disease take 

 alarming views of it and maintain that unless some- 

 thing unforeseen occurs to check its spread the chestnut 

 is doomed to extinction in the Atlantic States. 



There appears to have been no remedy discovered as 

 yet for its control. When a tree is once badly affected 

 it is doomed, and the only treatment recommended at 

 the present time is to prune back the affected parts, a 

 method of treatment which can only be effectual on 

 trees slightly affected. The disease is spread by minute 

 spores which are produced by the fungus. These are 

 formed continually and abundantly throughout the 

 growing season and are easily distributed by wind and 

 other agencies. , 



It is reported that the European, Japanese and na- 

 tive Chinquapin chestnuts are also subject to attacks 

 from this fungus. From the first we have been on the 

 lookout for this fungus in Massachusetts and have ex- 

 amined a great many chestnut trees which showed con- 

 siderable dead wood, and it has been reported inci- 

 dentally that the disease has been found in Massachu- 

 setts but we have not been able to substantiate this 

 report. It is possible that in the western or southern 

 part of the State it may be found but it is safe to say 

 the most of the State is probably free from it at the 

 present time. 



In Dr. Murrill's first paper he states that "it is pos- 

 sible that the conspicuous ravages of the disease about 

 New York State are largely due to the severe winter of 

 1903-'04 during which many trees of various kinds were 

 killed or injured." This statement is rather signifi- 

 cant inasmuch as in our own State a great many of 

 our native trees have deteriorated and died since this 

 period, and this is due not only to root killing but to 

 killing above ground. Among these troubles may be 

 mentioned the so-called "pine blight'' or sun scorch of 

 the pine which is associated with the severe winter 

 killing of roots. The decline of the ash, swamp 

 maple, oak, butternut, and in some cases the elm and 

 rock maple as well as white maple, together with the 

 cherry, apple, plum and peach, dates back to this 

 period. There has also been a large amount of dead 

 wood found in our native chestnuts showing that they 

 have not been in the best condition. 



Dr. G. P. Clinton, of New Haven, refers to a serious 

 trouble which affected the chestnut trees in the South 

 in 1825. at which time a large number of chestnut trees 

 died very suddenly, and more recent observations have 

 shown that the chestnut does not maintain its former 

 importance in that region. 



Thrips in Greenhouses 



Amherst, Mass. 



7!^ *Ju<r>iJL> 



A very valuable bulletin, the result of long and care- 

 ful investigation, 1- being prepared by Prof. A. C. Beal 

 and will soon be ready for distribution by the Illinois 

 Agricultural Experiment Station at Urbana. Follow- 

 ing 1- a summary of the contents. 



Thrips injur} to cut flowers in greenhouses is a 

 recent trouble. 



Thrips are very small winged, sucking insects which 

 lay their eggs in the green parts of plants. 



The "hothouse species" were not found, but a closely 

 related species is widely distributed. 



The great damage to roses and carnations is due to 

 the work of two common out-door species — Wheat 

 Thrips and Onion Thrips. (Euthrips tritici and T. 

 tabaci.) 



Cucumbers are injured by Onion Thrips, Thrips 

 tabaci-Lind. 



Observations made show T. tabaci to be the most 

 abundant species in greenhouses in autumn and winter, 

 but that Euthrips tritici becomes the most abundant 

 species in rose houses in summer. Thrips tabaci ap- 

 pear to prefer the carnation to the rose. 



Eggs are laid inside the calyx of carnations, on the 

 outside of the calyx of the rose, and in the tissues of the 

 lower side of the leaf of cucumbers and callas. 



Injury is caused by withdrawal of the sap from the 

 cells of the petals and leaves of plants, leaving white 

 blotches on colored flowers, causing a browning of petals 

 of white or light pink flowers, and a gray hoary appear- 

 ance to leaves. 



All species are more or less sensitive to bright sun- 

 light and generally seek shaded positions. 



Temperatures at night above 60 degrees are favor- 

 able to thrips and their appearance and worst injury 

 may be expected in the warmest parts of the house. 

 Conditions favorable to red spider are favorable to 

 thrips. 



Thrips injury is greatest in autumn and spring and 

 least in midwinter. 



Some varieties of carnations are more subject to at- 

 tack from thrips. 



Fumigation is slightly more effective than sprays. 



Hydrocyanic acid gas, one ounce to each 1000 cubic 

 feet of space is dangerous to young cucumber plants but 

 sufficient to destroy an average of 93 per cent, of the 

 thrips. 



Hydrocyanic acid gas, one ounce to each 3000 cubic 

 feet of space destroyed alcyrodes (whitefly) but only 

 eleven per cent, of thrips, while it did not injure the 

 plants. , 



Daily sprayings with nicotine insecticide on the 

 upper surfaces of the leaves and the spray syringed off 

 gave good practical results. Spraying thoroughly will 

 clean out thrips provided the plants will stand the hard 

 syringing necessary to remove the spray. 



Tobacco smoke is not a very efficient insecticide for 

 thrips. 



Sprays made with two-thirds of an ounce of any of 

 the stronger nicotine insecticides per gallon of water 

 gave promising results. 



Nicotine is the poisonous principle in the insecticides 

 used. Pure nicotine in very dilute solutions kills thrips 

 almost instantly when sprayed on them. 



The nicotine content is the factor determining the 

 value of a reputed tobacco extract or nicotine compound. 



