One grower, unable to get a dependable steam boiler, substituted two Propane-gas burners in two watertight flues, which looped along the bottom from the propeller end of the tank, down and back again and exhausted through a joint chamber. A fan in the chamber maintained a constant outward draft. Both burners are activated from a pilot light, but one is controlled by a thermostat and the other is manually operated as a booster heater.

Because high temperatures harm bulbs and low temperatures do not control nematodes, great care is needed in the operation of the equipment. The growers who do custom treating for other growers have installed recording thermometers so that a permanent record is made of each lot.

The present methods fora complete control of nematodes in bulbs consist of the presoak bath and the treating bath. The presoak bath is water maintained at 75 F., with Vatsol O. S. added at the rate of 8 ounces to 100 gallons of water. Infected bulbs are soaked in this bath for 2 hours immediately before treatment. Its purpose is to revive dried or inactive nematodes, which are more difficult to kill than active ones. Vatsol O. S. is a wetting agent that assures the thorough wetting of all bulbs immersed in the treating bath by removing air pockets from parts of individual bulbs or from between the bulbs. Newer wetting agents have not been tested in bulb treatments and should be avoided until it is definitely known that they will cause no injury. Vatsol O. S. has been used with good results and no apparent injury to the treated bulbs.

The treating bath consists of water with 1 pint of commercial formaldehyde solution U. S. P. to each 25 gallons of water. The bath is maintained at 110 F. for different periods in the treatment of narcissi, bulbous irises, and Croft Easter lilies.

An efficient treating bath must meet several requirements. Agitation or circulation must be adequate to insure a rapid and constant flow of the bath to all parts of the tank. That is accomplished by electrically driven propellers and by properly placed baffle plates in the tank, which assure an even temperature throughout the bath.

It is necessary to have the correct amount of treating bath to maintain the ratio of 4 to 5 parts of liquid by weight to 1 part of bulbs. In order to maintain the correct amount of formaldehyde solution, the tank is calibrated to determine the number of gallons required to fill it to its working level and the amount of water necessary to raise this level of the bath 1 inch. With that information at hand, the operator can add the correct amount of commercial formaldehyde when the bath is first prepared and can also determine the correct number of gallons of water and amount of formaldehyde solution to add between runs. If steam is discharged into the bath as a heat source, the bath is measured before the valves are opened because it is necessary to know how much water is added by condensation of steam.

The concentration of 1 pint of commercial formaldehyde solution U. S. P. to 25 gallons of water must be maintained so as to complete the nematode kill and prevent the dispersal of rot organisms from one bulb to another during treatment. Exact amounts must be added to compensate for any water added to the bath, either by steam or other methods. The commercial formaldehyde solution should be clear and free of any waxy sediment or thickening. If it has been stored in a cool place such a condition may exist and is likely to result in an unreliable concentration. The bath solution should he replaced when it has an excess amount of discoloration, sediment, or both from the soil brought in with the bulbs, which usually occurs after 6 to 8 uses.

The proper temperature is 110 F. for narcissi, bulbous irises, and Croft Easter lilies. The bath temperature must not fall below 110 nor rise above 111 for the entire treatment period, if results are to be satisfactory. In order to maintain this exact control, a reliable mercury-type thermometer, checked for variation with the one used by the State horticultural inspector, is a necessity. The cheap, spirit type of thermometer is not reliable enough to risk with a tank of bulbs which may be worth several hundred dollars. Growers doing custom treating should also use a recording thermometer and keep the records.

Duration of treatment is determined in hours after the bath has been stabilized at 110 F.

Bulbous irises are treated for 3 hours. Bulbs must be harvested early (about the same time as King Alfred narcissi) and treated within 3 to 4 weeks, or before any evidence of root development or basal swellings start.

Narcissi are treated for 4 hours. Bulbs should be harvested early, when about one-third of the foliage is yet greenish. Planting stock should be treated within 3 weeks after harvest.

Post-treatment care of irises and narcissi should consist of immediate cooling followed by planting or drying. Bulbs must be placed in shallow, sterilized containers and located where adequate air movement will dissipate the stored heat and excess moisture.

THE BUD AND LEAF NEMATODE, Aphelenchoides olesistus, was reported by me in 1945 as a serious pest of Croft Easter lilies in the Pacific Northwest. I later found that the infection can be controlled by a 1-hour treatment in the bath and temperature as used for irises and narcissi. Best results were obtained when bulbs were harvested 8 to 10 weeks following full bloom and their bulblets treated within 3 weeks. Only bulblets were treated, because we found that older stock may produce an excess of basal bulblets as a result of treatment, especially in late season. Treated bulblets are cooled immediately after treatment and planted in the field. If that is not feasible, they are kept moist and cool in well-ventilated storage.

WILBUR D. COURTNEY, a Hematologist in the Bureau of Plant Industry, Soils, and Agricultural Engineering, is stationed at Puyallup, Wash.