Dr. Stuart has suggested that many fertilizer practices may be of greater benefit to the Fusarium than to the narcissus. Organic manures also were found to increase the amount of basal rot. Many organic manures contain purine ring compounds, such as uric acid, allantoin, guanidine, and adenine.

Some of the synthetic growth regulators have been recommended for use in fertilizers for bulbs to stimulate root growth. Stuart and I dipped narcissus bulbs in water solutions, or in tale,containing indolebutyric acid, naphthalene acetic acid, naphthalene acetamide, allantoin, guanidine, uric acid, and nucleic acid (which on hydrolysis yields a pentose, three pyrimidines, and two purines, guanine, and adenine) before planting in the field. Those bulbs had a much higher percentage of basal rot when dug the following year than did similar bulbs dipped in water or untreated. Furthermore, greater growth of the Fusarium occurred in nutrient solutions to which the materials had been added.

Temperature markedly influences the amount of basal rot. In the Netherlands and England losses due to basal rot in the field are not nearly so extensive as those along our east coast. Also, losses from basal rot are much less in the Pacific Northwest than on the east coast.

We have grown King Alfred narcissus at Beltsville, in soil temperature tanks at temperatures of 45 to 70 F. and learned that uninoculated plants grow best with soil temperatures of 55 to 60 . When inoculated plants were grown in the tanks, Fusarium infection was most rapid at the higher temperatures. There seemed to be a sharp break in the rate of infection between 55 and 60 . That correlates well with experience in the Northwest and the East. King Alfred narcissus bulbs grown in Beltsville in 1947 and 1949 had 26.6 and 25.8 percent of rot, compared with 5.1 and 6.7 percent of rot in similar lots of bulbs shipped to Puyallup, Wash., and grown there. Late spring and summer temperatures at Puyallup average 8 to 12 lower than at Beltsville. The lower temperatures are believed to account for the lower incidence of basal rot at Puyallup. Attempts to reduce soil temperatures by mulching practices at Beltsville did not reduce the severity of basal rot.

CONTROL OF BASAL ROT involves attention to a number of details. Rotation to avoid infested soil is one of the prime requisites. Bulbs should be harvested before soil temperatures get too high. In fact, a sacrifice in bulb size in order to dig early often is advocated. In handling the bulbs during digging, grading, and storage, injuries should be avoided, and bulbs should not be allowed to overheat. They should be stored in shallow layers in cool, well-ventilated storage houses. The rotted bulbs should be culled before and after storage. Quick drying of the bulbs immediately after they are dug helps reduce losses.

Soon after Weiss began the study of basal rot in 1926 he sought methods for controlling the disease. He demonstrated that the hot-water treatment for nematodes resulted in contamination of healthy bulbs and he added fungicides to the water to kill the spores. He found that formaldehyde or mercurials were effective, and the use of 5 percent formaldehyde in the water bath is now a regular practice.

Since nematodes are not always present, the hot-water treatment is not always used each year. Consequently some other treatment was needed to control the Fusarium. Chemical treatments are feasible at two different periods in the control of narcissus in early summer, between harvest and storage, or in the fall, before the bulbs are planted.

In the first tests, various mercurials proved superior. Mercuric chloride, calomel, Semesan, 2 percent Ceresan, and New Improved Ceresan were effective in reducing rot, but all caused some injury. Two standard treatments were developed a dip for 5 minutes in New Improved Ceresan (1 pound in 40 gallons of water) for the eastern sections, and a dip for 15 minutes in 2 percent Ceresan (1 pound in 8 gallons of water) for the Northwest. Such treatments have been credited with saving the narcissus industry in the East.

Treated bulbs far outyielded untreated bulbs. For instance, in a test at Beltsville, 200 King Alfred bulbs were treated with New Improved Ceresan in 1946. The bulbs were given the same treatments in 1947, 1948, and 1949. After harvest and storage in 1950, there were 821 healthy bulbs.

Although growers were reluctant to use treatments before storage because of the danger of severe injury to flowers produced the next season from treated bulbs, heavy losses from basal rot in storage turned the attention of workers to such treatments. They developed the double dip (before storage and before planting) with New Improved Ceresan. Treatments applied 3 days after the bulbs were dug gave best protection against storage rot but also induced maximum flower injury. Late treatment, 15 days after digging, caused no flower injury but gave little rot control.

A 5-MINUTE DIP in Mersolite 8 (phenyl mercury acetate) or in Puratized Agricultural Spray (phenyl mercury triethanol ammonium lactate) is as effective in controlling basal rot as the Ceresans but does not cause flower injury. Mersolite P, a phenyl mercury acetate dust, also has been effective. Arasan dust or Arasan SFX have been fairly effective when a low amount of Fusarium was present in the stock. The organic mercurials, Mersolite 8 and Puratized Agricultural Spray, have come into commercial use as pre-storage and preplanting treatments in North Carolina and other bulb-growing areas. Bulbs have been treated with Mersolite 8 immediately after digging and have been kept wet for 10 days with no detrimental effect on flowering. Furthermore, bulbs dug immature were not injured by treatment with Mersolite 8, although there was a reduction in bulb yield the following year because of the immaturity.

W. D. MCCLELLAN was trained in plant pathology at the University of California and Cornell University. He was on the staff of the University of Maryland in 1940 and 1941, and was an employee of the the Bureau of Plant Industry, Soils, and Agricultural Engineering from 1941 to 1951, when he became director of research for Mid-State Chemical Supply Co., Lindsay, Calif.