CONTROL OF EELWORM IN TOMATO-HOUSES.

New Zealand Journal of Agriculture, Volume XXIII, Issue 4, 20 October 1921, Page 224

CONTROL OF EELWORM IN TOMATO-HOUSES.

EXPERIMENTS AT LOWER HUTT.

Eelworm infestation is becoming a serious menace to various crops grown both in the open ground and in glasshouses. • Until recently the chief means of control was carbolic acid, but this remedy is expensive, as well as having some further drawbacks. For example, plants cannot be grown in soil treated with carbolic acid until the latter has evaporated, which takes some weeks. Carbon bisulphide is being increasingly used in eel worm control in other countries, and has several advantages over carbolic acid. Last year arrangements were made with Mr. C. W. Howard, Lower Hutt, to conduct some experiments in his tomato-houses, which were infested with eelworm. The tests were carried out entirely by Mr. Howard, who furnishes a report as under.

Horticulture Division.

MR. HOWARD’S REPORT. During the 1920-21 season a series of experiments was undertaken to test the efficacy of carbon bisulphide as a means of controlling eelworm in tomato-houses, a glasshouse measuring 200 ft. by 40 ft. by 14 ft., and having a single-span roof, being set aside for this purpose.

The soil of the house was a made —rotten rock, clay turf, roadscrapings, weeds, hay, green grass, green clover, green oats, and stable manure all entering into its composition. Previous crops grown in the house had been fourteen of tomatoes and ten of French beans, also some experimental vegetable plants. Each of these crops had received heavy applications of artificial manures —phosphates, potash, nitrogen, copper, iron, and sulphur —and also of burnt lime. All crops had been good with the exception of the last two crops of tomatoes, which were poor on account of eelworm infestation. .The first of these poor crops was from seed grown in eel worm-infested soil, and served to introduce the pest into the soil of the tomato-house. The following crop also failed, leaving the soil very badly infested with eelworms at the time the experiments. commenced. , For the purpose of the experiments the glasshouse was divided into four plots, each of which received different soil-treatment. Two of the plots were used to test different methods of applying carbon bisulphide, a third was treated with carbolic acid for purposes of comparison, while the fourth,' the control plot, received no special soil-treatment. On ist April, 1920, the following treatments were given to the plots : Plot 1 (80 ft. by 40 ft.) : Holes were made in the soil 20 in. apart, and | gram of carbon bisulphide was poured into each hole, which was. then plugged. The soil was then watered all over. Plot 2 (80 ft. by 40 ft.) : The soil of this plot was loose, and was sprayed in strips measuring 3 ft. by 40 ft. with the'same aggregate quantity of carbon bisulphide as was used on plot 1. The ground was then flooded with water and afterwards rolled with a heavy roller. Plot 3 (36 ft. by 40 ft.) : Carbolic acid was sprayed on the soil, which was then heavily watered. Plot 4 (4 ft. by 40 ft.) : This was the control plot, and no soiltreatment was given. It was situated at the end cf the house, and was boarded off from the treated portions. , : In order to ascertain the effect of these treatments on newly-set-out plants and- on the germination of seeds, plantings were made on each of plots 1,2, and 3of ten bean-seeds and ten tomato-plants on the day following treatment. Similar plantings were also made each day for a further twelve days. On plots 1 and 2 normal growth took place, except that of the beans sown on the third day only three sickly plants came up. On these two plots the tomato-plants at first appeared sickly, but afterwards recovered and grew strongly. On plot 3, treated with carbolic acid, both beans and tomatoes failed entirely. A further treatment of the soil of the three plots on 15th April, followed by similar plantings of beans and tomatoes, confirmed the results of the first test. When carrying out the second spraying of plot 2 some of the bisulphide used got on to the tomatoes already planted and caused a certain amount of damage to the foliage. - Tomato-plants were set 'out on plot 4 on ist May and ist June respectively, but as eelworm-galls soon developed on their roots they were pulled out. ■ ■ , After these tests the plants remaining were rolled in, the plots cultivated, and the ground then left fallow. On 14th July the interior

of the house was bastard-trenched to a depth of 2 ft. 6 in., and applications of potash, phosphates, nitrogen, and 'lime made. The house was also fumigated with cyanide of potassium. In addition to the work on the plots, several kerosene-tins were obtained, cut lengthwise into halves, and each half filled with untreated eelworm-infested soil. ’ A quantity of carbon bisulphide, proportionately four times as great ,as that used on the plots, was then poured into each tin, and four bean-seeds and one tomato-plant were immediately planted in each. All came away well, but the beans, after setting flowers and showing promise of a good crop, had to be removed to make room for the tomatoes. These latter grew to a height of 6 ft. and set five and six bunches of well-grown fruit, only lack of room preventing further growth. For the purpose of the main experiment tomato-seed of the Chemin Rouge variety was sown early in June. On 14th June some of the plants were pricked out into boxes'containing soil which had been treated with carbolic acid in April and held in readiness for this purpose. Others were transferred to boxes of soil which had recently been treated with carbon bisulphide. Planting-out was done on Ist August, when the four plots in the tomato-house were filled. Owing to the plants in the boxes of ’ bisulphide-treated soil having suffered severely from frost on 26th June, it was necessary to set out in plots 1 and 2 plants which would otherwise have been rejected. In all treated plots the plants. made good growth and produced an exceptionally fine crop, picking commencing on sth November and continuing until the following July. The plants were unusually free from disease, except for a rather heavy infection of black - stripe, and on examining all roots for traces of eelworm-gall the percentage of infection was found to be only 1-2, or 12 in 1,000. Even these infected plants bore a good crop. On plot 4, as indicated, no soil-treatment had been given, but otherwise the plants were grown as bn plots 1,2, and 3. Here the eelworm took complete control, resulting in an absolute failure of the tomato crop. t ' CONCLUSIONS. ‘ These experiments demonstrated that both carbon bisulphide and carbolic acid are effective as a medium for soil-treatment, in control of eelworm, but that at least two years are required to effect a complete clearance. Of these two remedies the bisulphide treatment should prove more suitable for the commercial grower, owing to the fact that plants cannot be grown in soil treated with carbolic acid until’ some ten or twelve weeks after the application has been made. Both methods of using —spraying the, surface of the soil, and saturating it by means of holes —are suitable, and are equally effective, but with a hollow rod and two valves the holes can be done quicker. In both cases the house should be closed during and for some hours after treatment, and care should be taken to prevent the highly inflammable gas given off from becoming ignited, no smoking being allowable. ■ '' Carbon bisulphide apparently does the plants no harm, and even has a fertilizing effect, it being noted in all cases where it was used that plants at first showed a forced growth as though from an excess of nitrogen; but afterwards hardened off in a normal manner.