Through the use of a dye solution, evidence was obtained that a liquid disinfectant may be forced into the narcissus bulb parts invaded by nematodes and fly larvae by immersion in vacuo.An investigation of the lethal properties of solutions against nematodes and their influence upon bulb growth led to the selection of a silver nitrate solution as a promising disinfectant, but owing to instability of silver nitrate in the presence of chlorides and other substances in tap water and in dirt clinging to bulbs, its use had no commercial possibilities. However when silver salt was combined with potassium cyanide in the ratio of 1 to 3 by weight, an effective solution of satisfactory stability was obtained.A solution of silver nitrate 0.05% and potassium cyanide 0.15% by weight, forced into narcissus bulbs by an evacuation process, effectively destroyed bulb nematodes and bulb fly larvae without significant injury to bulb growth under greenhouse conditions.Field tests with bulbs treated in silver nitrate-potassium cyanide solutions resulted in the reduction of infection from 26.8 to 1%, a 96% control, and no evidence of injury in the foliage or bloom was detected.
Out of 26 strawberry varieties, only Sierra was resistant to Verticillium albo-atrum R & B. Climax, Marshall, Magoon, and Auchincruive No. 6, however were tolerant. Climax, Marshall, Northwest, Oberschlesien, Perle de Prague, Red Crop, Sierra, and Temple, when selfed, yielded a high percentage of resistant seedlings, suggesting that these varieties have promise as parent material in the breeding of commercial varieties for Verticillium wilt resistance. Fragaria chiloensis from two geographical areas yielded resistant seedlings in contrast with F. vesca americana which produced neither resistant nor tolerant seedlings. F. virginiana yielded tolerant but no resistant seedlings.
The meadow nematode Pratylenchus pratensis has been isolated from root lesions of narcissus, strawberry, apple, cherry, and raspberry in British Columbia. When apparently freed from associated fungi, this species reduced the growth of potato, carrot, red clover, tomato, spinach, and violet seedlings by 50 to 75%, and oat seedlings by less than 4%. In parallel experiments, the commonly associated fungus Cylindrocarpon radicicola as a pure culture reduced growth by only 6 to 11%. The inhibition of growth by the fungus and nematode as a mixed culture was usually greater than the sum of the reductions as pure cultures.The nematodes were separated from associated fungi by planting segments of infested oat roots in plate cultures of powdered peat moistened with a 0.1% solution of malachite green. When the oats planted in this medium had germinated, the nematodes moved from the root segments through the fungicidal medium into the roots of the oat seedlings. These nematode-infested roots proved to be free from the fungi and bacteria naturally associated with the nematode in field infestations.The adult and all the larval stages of P. pratensis proved to be capable of entering the roots of oat seedlings.
The immersion of iris bulbs in water at 110 to 112° F. for 60 min. effectively destroys the bulb nematode.The safe period for nematode destruction in iris by hot water lies between July 26 and August 9. Thereafter injury to the bulbs occurs and is progressively greater as the immersion dates are delayed.
Barley is suggested as a detector crop for the presence of living nematodes, Tylenchus dipsaci, in soil, owing to rapid development of nematode disease symptoms on barley.A satisfactory source of inoculum consists of the white masses of coiled nematodes that can be seen when the basal plate is removed from badly diseased narcissus bulbs. These masses remain viable for six months or longer when removed from the bulbs.Low temperatures and high light conditions favor the development of the nematode disease symptoms in barley seedlings, after nematodes are transferred from narcissus bulb to autoclaved soil planted with barley. Such barley seedlings were broad-leaved and stocky. Under low light and high temperatures, conditions that favor the development of spindly seedlings, the nematode disease symptoms are inconspicuous or absent.Few chemicals appear to be lethal to the bulb nematode. Of 100 tested only phenol, silver nitrate, and potassium or sodium bisulphite were lethal at dilute concentrations.
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