Chloropicrin for Nematode Control hl. 0. JOHNSONAND G. H. GODFHEY Experiment Station, Association of Hawaiian Pineapple Canners, University of Hawaii, flonolulu, Hawaii
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IT27 the scriior aiitlior about 20 months after plantChloropicrin treatrnenf of rool-knot (Heleroderu ing, manifested itself by striktreated soil from bad failure radicicola) infested soils in pineapple fields of areas in p i n e a p p l c fields ing i n c r e a s e s in yields. I n Ifauuii ha.ce brought about striking reductions with chloriipicrin and obtaiiied fact, the increase in vigor was in infestdiou and eqnully striking increases in remarkably increased vigor of restill manifest in some plots a t vigor of plant growth and in yield of pineapples. sulting pineapple-plant growth, first ratoon-crop stage, 1 year later. as compa.red with untreated conWhereas no claim is made that nematode control Comnletelv satisfactorv trols. The soils were in root obis the only fuctor inuolved i n the improved plant quantititive data on effects o n servation boxes, and it was evigrowlh, this paper deals wilh that faetor alone, dent that the increased vigor plants are lacking, hut observaand includes actual measurements, by means of was due to a direct effect on the t i o n s on o n e o r t w o of t h e cowpea indicator crops, of extent of nematode roots. Among the results was a experiments are r e c o r d e d for what they may be worth. In notable decrease in the amount reduction. The most efleclive trealrnenk were of nematode root knot in the one test that showed, by striking those which consisted of the introduction of treated boxes. This was verified differences in p l a n t g r o w t h , chloropirrin in liquidform into holes 5 to 6 inches r e p e a t e d l y by similar experio u t s t a n d i n g value from the deep, spaced I8 inches apart and covered imtreatment, chloropicrin had hew merits without, however, any mediately with mulching puper, the rates of apactual measurements being taken applied a t the rate of 180 pounds of the a m o u n t of d e c r e a s e . per acre. Three adjacent pineplication being I63 pounds or more per acre. These preliminary tests led to apple plants selected as reprecarefnllv c o n d u c t e d field exsentative were removed intact. periments tlie same year (1'327) and subsequent years by roots and all, from this plot, and three from a compathe senior author, wliich showed striking increases in gr0wt.h rable control plot, just following harvesting the fruit when the and yield of fruit. This paper discusses in detail certain plants were approximately 20 months old. Greater extent of the field tests wliicii were st.ndied by tlie junior author, of root growth, including abundance of fine feeding-branch primarily from the point of view of nematode control. Re- rootlets in the treated plots, was strikingly evident. Tlie sults are reported in terms of actual nematode reduction, three control plants showed Ileterodera radicicola infestation measurements being by means of indicator crops.' in 90 pcr cent of all roots, while treated plants showed only While chloropicrin has been used more or less extensively 30 per cent infestation. These differences in root systems for fumigation, its use for soil treatment has been very limited, were jrnraileled by very obvious diffrrences in the aerial parts as indicated by the chloropicrin bibliographies prepared by of the plants. The untreated plants had an average lateral Roark (9) and Gersdorff (1). The present authors bare not spread or total width of 45 inches and a height of 35 inches; been able to review thc original papers cited by these men, the t.reatcd plants showed 55 inches spread, and 45 inches but refer to their annotations on the work of Piutti and height, a difference of well over 20 per cent in both measureBernardini, Spencer, Matthem, Russel, Hasson, Dingier, ments. I'ineapple-yield differences were striking. The 180Fryer, Parker, Feytaud, and Anuie Matthews, ~rartieulltrlyto pound cliloriipicrin bed yielded in plant crop 11.8 tons more Matthem (8) who appears to have included nematodes in than the control, ib difference of 57.0 per cent. Figure 1 lier studies. None of this work seems to have been followed illustrates the condition of these two rows at first ratoon-crop stage, the third summer after planting. by practical field applications. In another experiment chloropicrin applications were made P~EI,I?.~INARY EXPERI~LIENTS ON PINEAPPLE by means of the Vermorel applicator, at rates varying between 45 and 185 pounds uer acre, Most of the preliminary field tests referred to above, in which chloropicrin was introduced into nematode-infested soil in measured doses by mems of a Vermorel injector, demonstrated remarkable increase of plant growth over the untreated controls within 2 or 3 months after p l a n t i n g . This increased vigor p e r s i s t e d throughout the growth of t h e p l a n t , a n d a t p l a n t - c r o p stage, 2 Tim iunior author is preim.rin4 B paper on t h e indiaiitor-crop method
of determining effeots of v ~ i i o umil ~ treatments on nematode inleststion of t h e mil, pointing out its useluloess nnd its iimitntions.
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(1) of the twelve plants examined, the two from the bed of the paper snd in the three spaces between pineapple rows receiving the heaviest application of chloropicrin (bed 17, through the paper. On March 26 to 31, 1931, the indicator 180 pounds per acre) ranked first in vigor of top and root plants, being approximately 30 days old from seeding, were growth, and ranked lowest in amount of nematode root knot removed from the soil by means of trowels with the root and of root-lesion nematode infestatioii (Z'ylenchta bracl~yz~rus systems as complete as possible. These plants were tied in Godfrey); (8 plants from beds 2 and 16 (controls) ranked last bundles and laheled as to source. There were in all some in vigor of growth and among the highest in amount of rooL Lfiuteen thousand of them from the two locations. The knot and T?ilenehus: other treatments examined, ranging from plants were taken to the laboratory, and height to the growing 120 to 145 pounds per acre, variously applied as regards point was measured; tops were removed, and plants, still in spacing, etr:., gnvr intermediate results; and (3) yield records labeled bundles, were immersed in 2 per cent (commercial) formaldehyde. The roots were then available for examination at leisure as to degree of nematode infestation. H e i g h t of p l a n t s in each bed and average degree of infestation of the cowpea roots sere recorded. Readin@ on infestation were obtained in the form of numbers of plants in each of several different classes as to degree of infestation, ranging from 0, through trace (1 to 10 galls per plant), slight (10 to 50 galls), medium (50 to 1W galls), and heavy (100 galls up per plant.). This was an arbitrary classification which appeared to meet the needs of this particular experiment satisfactorily. The figures from these F I G U S E 2. I I e L E a A N o TEST No. 1 tabulations were used in the preparaChart ehows peiceiitnaea of planta with diffeient tion of the charts shown in Figures 2 to degrees of iieinz+tode iniestatioa ioi each of the Same order oftreptmente a Figure 2. but aevemI diKcioilf oliioropicrin traatmente. 5, which show much more clearly than additional %ppliaatron of cbloropicnn at mle oi 110 pounds per sore between beds. do tabulations the results of the exrmrirnrnk
showed a difference in plant crop US T.1 tons per acre over the average of controls, a difference of 21.8 per cent in Ea,wr of the best treatment.
The charts are self-explanatory. They show eleuriy the benefits, in the way of enhanced plant growth and decreased nematode infestation derived from the applications of chloropicrin, partieolarly the applications of 163 pounds or
EXPERIMENTS WITH COWPEA INDICATOR I'ursuant to these continuously favorable results, further experiments were initiated and an effort was made to measure inon: exactly the effects of treatments on nematodes. Treatments were applied in two different localities in the leading pineapple section in the vincinity of Wahiawa, on Oahu. Applications were made by means of the usual Vermorel injector in various dosages in a series of standard plant beds through wide (54-inch) mulching paper. Two weeks after treatment, pineapples were planted according to the four-line system. I n this planting system, four lines of plants were set through the one line of Winch paper, the lines of plants being 16 inches apart and the plants 16 inches apart in the row, plants and spaces alternating in adjacent lines. Actual applications were made according to the plan indicated in Table I, the term "bed" applying to the plant bed of four rows of plants under paper. In eases in which more than one bed received the same application, samples were taken only from the middle one of three or frolo tile one of two which lay adjacent to a bed wit11 a higher rate of application, in order to eliminate in so far as possible contaminations from controls or inadequate lower treatments. Of such cases in Table I, beds 1, 4, 6, 8, 10, 13, 16, 18, 20, 22, 35, and 37 were selected for sampling. In February, 1S31, 4 months after planting, d8crences in pineapple growth in dXerent plots were already stribingly evident. At this t.ime, in an effort to get an early determination on effects of the treatments on nematode infestation, an indicator crop, rather than pineapple plants which would have to be destroyed, was employed for root examination. For this purpose, Pihippoorwill cowpeas were seeded at the edges
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FIGURE4. K r r ~ rTEsr ~ No. 1 more per acre. Without attempting a detailed statistical analysis of results, certain conclusions that would appear to be obvious because of numbers concerned are specified. CONCLUSIQNS 1. The control plots (untreated) cunsistently show the lowest percentages of roots free from nematode root h o t , and correspondingly the highest percentages with heavy infestation. 2. The curves for freedom from infratation correlate directly to a fair degree with quantities of chloropicrin a p plied. Certain seeming inconsistencies in this respect are to be explained in part by differences in met.hod of application,
I S D U S T 11 1.4 L
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tests of which were an important part of the experiment. In bed 6 throughout, for example, chloropicrin a t the rate of 204 pounds per acre in the plant bed was applied in holes 24 inches apart; in bed 4,receiving only 178 pounds per acre, points of application were 18 inches apart. Figures 3 and 4 show better control with the lighter of the two applications. It would appear that in these two soils the better distribution of the chemical through the soil with the closer points of application more than balanced the benefit derived from the larger quantity. The same relationship existed between the 125- and the 110-pound applications, and Figures 2 and 5 show a distinct advantage for the lighter and closer application. Both applications, however, were irregular in effectiveness, and it was evident that many spots were not reached effectively by the chemical. 3. Curves for higher degrees of infestation are roughly parallel throughout with the curve for freedom from infestation. It should be noted that the differences between lightly and heavily infested plots would be much more accentuated if each figure for percentage were appropriately “weighted” by multiplying by a factor representing average number of galls per plant in its class. For example, the horizontal-lined shading, if assigned the value 5 for each per cent of total number of plants examined, would call for a factor of 30 (average of 10 and 50) for the diagonal shading; of 75 for the cross hatching; and of 150 for the solid black. These figures are arbitrary of course, since they represent not actual but theoretical means. The picture of comparisons would be very much the same, however, if minimum instead of theoretical mean figures were used in each class. On the selected basis the total infection portion of column 1, Figure 2, would be approximately 3600, as compared with 534 for column 2 and 768 for column 3. These figures obviously present a truer picture of relative amounts of infestation left alive than do the total lengths of all shaded portions in the charts. The benefit derived from the heavier applications of chloropicrin in the xay of reduced nematode infestation is therefore considerably greater than is a t first apparent. TABI.~ I. 1 ’ 1 - 4 ~
OF
CHLOHOPICRIX APPLIC~TION USED
IN
EXPERIMEYTS 1 .4ND 11
CHLOROBEDE 1, 2 3. 4 5, 6 , i
8, 9
10, 11 12. 13, 14 15, 16, 17 18, 19 20,21 22, 23 21, 26 26
27, 28 29 30 31 32 33 34 35, 36 37.38
PICBIK UNDER
PAPER Lb. per acre 0
178 204 163 136 0 125
110 91
83 0 0
178 204 163 136 125 110
94
83 0
SPACIIVG OF POINTE OF APPLICATION
Inehea Controls 18 (12 frqm edge) 24 (in 3 lines. center and either edge) 18 (in 3 lines) 24 (in 2 lines) Controls 24 (in 3 lines) 18 (in 2 lines) 36 (in 2 lines) 24 (in 2 lines) Controls Control
18 (in 2 lines) 24 (in 3 lines) 18 (in 3 ljnes) 24 (in 2 lines) 24 (in 2 lines) 18 (in 2 lines) 36 (in 2 lines) 24 (in 2 lines) Control
REMARKS
Subsequent beds given additional application of 110 Ib. per acre in ”middles,” between plant beds Total per acre, 288 lb. Total per aore, 314 Ib. Total per aore 273 Ib. Total per acre: 246 lb. Total per acre, 235 Ib. Total per acre, 220 Ib. Total per aore, 204 lb. Total per acre, 193 Ib.
4. An expected advantage in favor of those areas receiving an extra application of chloropicrin in the “middles” between beds did not materialize, a t least not to an extent commensurate with the quantities involved. Figure 3, as compared with Figure 2, appears to show such advantage, but the control plots show equivalent or greater differences; therefore the better control in Figure 3 cannot be considered as significant.
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Figure 5 shows no such advantage whatever over 4 in the heavier applications, but a seeming advantage in the lighter, in which the bed-application was inadequate of itself. 5 . Measurements of growth of indicator crops mere made on all the experimental areas, and results are recorded in the form of graphs a t the bottoms of Figures 2 to 5 . I t is to be noted that a line drawn through the points for height of check plants will almost without exception orient the higher applications with consequent increased growth well above it. Cost considerations are of course important in connection with any chemical treatment of the soil. .1Pacific Coast firm has quoted a tentative price of 65 cents per pound for chloropicrin in large quantities laid down in Honolulu. The agent of an eastern firm is selling locally for 84 c t d s per pound. At the lower figure an application of 140 pounds per acre, which appeared t o give highly satisfactory results in recent field tests, would make the cost something like $90.00 per acre. Improved methods of application which are being developed may lower the quantity required per acre. Likewise increased consumption will probably lower the costs. Cost of applica-
FIGURE 5. KUNIATESTNo. 2 Same order of treatments as Figure 4, but additional ap lication of chloropicrin at rate of 110 poun& per acre between beds.
tion, even with hand applicators, will probably be less than $5.00 per acre, and can be lowered by machine methods. The cost figures given, when compared with yield increases, would appear to justify extensive use of the material on badly infested land. Experimental work on chloropicrin for nematode control is continuing a t the Pineapple Experiment Station and a t various pineapple plantations.
ACKNOWLEDGMENT dcknowledgment is due Helene M. Hoshino and Holoaumoku Gittel for their extensive routine examinations of plants from these experiments.
LITERATURE CITED (1) Gersdorff, W. A, U. S. Dept. Agr., Bur. Chemistry and Soils,
Supplement to Chloropicrin Bibliography, Oct., 1930 (mimeographed). (2) Matthews, D. J., Mrs., Exptl. Research Sta., Siirsery Market Garden Industries’ Devel. SOC.,Ltd., Turner‘s Hill, Cheuhunt, Herts. 6 t h Ann. R e p t . , 18-21 (1929); l b i d . , 6th A r m . Rept., 45-51 (1930). (3) Roark, R. C., U. S. Dept. Agr., Bur. Chemistry. C h r m Bihli. ography 1 (1926). RECEIVED October 3, 1931. Published with the approval of the Director as Technical Paper 31 of the Experiment Station of the Association of Hawaiian Pineapple Canners, University of Hawaii.
