F. M. Blodgett

Relative effects of calcium and acidity of the soil on the occurrence of potato scab

ConclusionsIn these rather simple exploratory tests, no reason was found for believing that lime has any effect on potato scab other than through its effect on the alkalinity of the soil.The general relation of acidity of the soil to scab was similar to that previously reported from a field survey.The amount of scab was reduced by extremely heavy applications of lime giving pH values of the soil (about 9.0) higher than those found on the survey (8.0–8.3) where scab was not troublesome.

A second report on the effect of agronomic practices on the incidence of rhizoctonia and scab of potatoes

SummaryThe results obtained in three rotation experiments in New York State in 1939, confirm the report made in 1938. They are as follows:More potato tubers bore sclerotia ofRhisoctonia where potatoes were grown continuously than where they were grown in longer rotations.Where potatoes were grown continuously, the largest percentage of tubers were affected withRhizoctonia where they were grown without commercial fertilizer, manure or cover crop. The addition of fertilizing material in any of these forms reduced the percentage of tubers affected, and the greatest reduction was secured on plots where all of these fertilizing materials Were used together.At the only location where the pH of the soil was such as to favor scab, the largest amount occurred on plots which received no fertilizer, manure or cover crop. At the other locations small increases in scab occurred on plots Which had been previously limed for clover. The largest increases were obtained on plots which received both manure and lime. Manure alone has caused a small increase at Malone.

The effects of some agronomic practices on the incidence of Rhizoctonia

SummaryMoreRhizoctonia occurred on potato tubers where potatoes were grown on the same plots for three successive years than during the longer rotations.On plots where potatoes were grown for three years in succession, the use of 1000 pounds of 5-10-5 fertilizer reduced the number of tubers showingRhizoctonia in the two locations where the rotations were such that this point was tested.The application of stable manure reduced the amount ofRhizoctonia on the tubers at all of the places.A rye cover crop also reduced the amount ofRhizoctonia in two of the three places.The best results in controllingRhizoctonia where potatoes were grown repeatedly on the same plots were obtained by combining all of these practices, that is the use of commercial fertilizer, stable manure and cover crops.

Three years’ results using bordeaux mixture with reduced amounts of lime as a potato spray

SummaryThe results both in upstate New York with Rural potatoes and un Long Island with Green Mountains seem to consistently favor a Bordeaux mixture with less lime than copper sulfate.In one experiment at Pittsford in which the amount applied was also varied, there seemed to be a clear indication that with mixture, not so much copper per acre is necessary to give maximum yields as with mixtures containing larger proportions of lime.So far as our experience goes in these three years in the three localities, it appears safe and desirable to reduce the lime in the mixture, either stone or hydrated, at least to half as much as the amount of copper sulfate.

Potato spraying and potato scab

ConclusionsFor the past two years marked reduction in the percentages of potato scab have been obtained in certain fields by spraying potatoes with bordeaux mixture.Several ways in which spraying might cause such results are suggested. The delay in tuber-setting and enlargement caused by spraying, might throw these phenomena into a period when higher soil moisture prevails, thus reducing the amount of infection. Tubers from sprayed plants have a higher total nitrogen and copper content, either of which may have some influence on infection. Reduction in the population of flea-beetles may reduce inoculation. Sprayed plants wilt more in hot weather and this may bring about changes which make the tubers more scab-resistant.

Effects of bordeaux mixture and pyrethrum dust on leafhopper control and yields of potatoes

A t the t ime it was r epor ted [ M a d e r and Blodget t , ( 2 ) ] that 75 to 80 pounds of copper sul fa te in the fo rm of b o r d e a u x m i x t u r e to the acre du r ing the season gave m a x i m u m yields of pota toes , some evidence was at hand to indicate that the increase in yield, in large par t was independen t of l ea fhopper control . I n o r d e r to obta in fu r the r i n fo rma t ion on this poin t expe r imen t s were conduc ted in which increases due to the effect of copper on the p lants could be sepa r a t ed f rom increases due to insect control. I n one case p y r e t h r u m dus t was appl ied for l ea fhoppe r control to a sect ion across the var ious b o r d e a u x sprayed plots and checks. In this way it was hoped to obta in a compar i son of the action, of d i f ferent amoun t s of copper app l ied as b o r d e a u x m~xture in the presence of few insects as compa red with the same b o r d e a u x mix tu re s and checks in a reas on both sides where the insects were not cont ro l led independen t of the bor d e a u x mix tures .

Further field experiments on potato scab control in Western New York

SummaryAll data have been obtained from experiments in a region characterized by soils of rather alkaline reaction, usually at least pH 6.0.Formalin seed treatments have consistently given small reductions in potato scab when compared with the untreated check plots.Mercurial seed treatments have given small but significant increases in scab over the checks and formalin treatments.Mercurials added to the soil have, in all cases, increased scab.In Western New York tuber defects are markedly decreased by the use of sulfate of ammonia in the fertilizer.In limited trials tetrachloroethane and hexamethylenetetramine showed no promise of scab control.Netted Gem possesses a rather high degree of resistance to serious injury by potato scab.Slight differences in scab resistance apparently exist within the Smooth Rural group of varieties.White Blossom Cobbler is considerably more resistant than is the Irish Cobbler variety.

Reduced toxicity of cuprous oxide toPhytophthora Infestans (Mont.) DeBary by the addition of certain insecticides

A dust combination that would give effective insect and disease control in one operation would be of definite advantage to potato growers. Experimental work along this line has now been conducted for four years on Long Island where, for various reasons, there is a particular need for such a program. These trials to date have centered largely in various combinations of pyrethrum, rotenone, sulfur, and cuprous oxide. Information on insect control has been obtained every year, but this past season gave us the first opportunity to study the effect of some of these dust combinations on late blight control. The data obtained appear to be rather clear cut and of sufficient importance to present at this time. The results to be presented were obtained from a large-scalo field experiment in which the 6-row plots were dusted six times during the growing season with power dusting equipment. The experiment was one of factorial design involving all possible combinations of pyrethrum, rotenone, sulfur, and cuprous oxide*. The dust mixtures were prepared just prior to the start of the experiment and were used throughout the season. Blight counts were made on two separate dates on the plots dusted with the copper-containing dusts (Table I ) . I t is evident from

Program of the twenty-eighth annual meeting of the potato association of america December 29–31, 1941

PROGRAM OF THE TWENTY.EIGHTH ANNUAL MEETING OF THE POTATO ASSOCIATION OF AMERICA December 29-31, 1941 P,esident, F. M. BLODGETT, Cornel/ University, Ithaca, New York. Secretary, WILLIAM H. MARTIN, Rutgers University, New Brunswick, N. 1. M~onday Afternoon, Joint Session with American Society for Horticultural Science, December 29, 2:o0 P. }r Room 212, Hyer Hall, Southern Methodist University. JULIAN C. MILL~, Chairman I. Importance and Prevention of Potato Seed Piece Decay. (15 rain.) O . H . ELMER, Kansas State College, Manhattan, Kansas. 2. Non-virus Leaf Roll of Irish Potatoes. (I2 rain., lantern.) E. L. LECLERG, U. S. Department of Agriculture, Baton Rouge, Louisiana.

The response of different varieties of potatoes to different amounts of copper in a modified spray program

SummaryWorking with the Irish Cobbler, Rural Russet and Green Mountain varieties of potatoes at Pittsford, N. Y., it was found that all these varieties respond to copper treatments in the form of bordeaux mixture to approximately the same extent in final increases in yields. Using a Bordeaux mixture composed of the equivalent of half as much quick lime as copper sulfate, and applying most of the copper early in the season, there appeared to be no advantage in using more than a total of 60 pounds of copper sulfate per acre during the season.All copper-sprayed plants retained more tubers per plant than unsprayed plants of the same variety.All varieties showed evidence of a retardation in tuber development due to spraying. The retardation was less pronounced with the Cobblers and most pronounced with the Green Mountains. In the Green Mountains, the unsprayed plants yielded more than the sprayed until after September 21.