WOOLLY APHIS.

New Zealand Journal of Agriculture, Volume VI, Issue 5, 15 May 1913, Page 520

WOOLLY APHIS.

SALT FOR THE CONTROL OF THE DISEASE

T. W. KIRK, F.L.S.

F.L.S

At the Conference of Orchard Instructors held in August, 1911, it was mentioned that several growers believed they had succeeded in controlling American blight by the use of , salt. It was therefore arranged that the Instructors should endeavour to secure the cooperation of one or more growers in each district in order to carry out experiments in this direction. I suggested they should spray one tree with salt solution, and leave one untreated near it; take another tree and apply a dressing of salt to the soil; and a fourth tree which- should be sprayed with the salt solution, and also have an application of agricultural salt •' to the soil. It was arranged that from lb. to 4 lb. of salt should be used for the soil-dressing’ according to the size of the tree.

The co-operation of the Fields and Experimental Farms Division was also solicited. Following are the reports received, from which it will be seen that the tests do not support the belief that dressings of salt will control the woolly aphis

Summary or Reports op Experiments carried out at the Experimental Farms AND UNDER THE DIRECTION OP. ORCHARD INSTRUCTORS IN PRIVATE ORCHARDS. J. W. Collard, Orchard Instructor, Whangar ci.

W. R. L. Williams, Orchard Instructor, Auckland.

Acting on your instructions, I treated three affected trees with salt for the control of woolly aphis. There were a number of other trees similarly affected adjoining them, and which were not treated for comparative purposes. (a.) Sprayed with salt at the rate of 1 lb. to 4 gallons water. (6.) Sprayed with salt at the rate of 1 lb. to 4 gallons water and the soil top-dressed around with .3 lb. salt, (c.) Soil around top-dressed with 3 lb. salt. '

An examination was made on the 26th January, 1912, with the following results : (a.) Showed a considerable amount of live woolly aphis, although probably a slight

improvement. (b.) Woolly aphis still pretty bad, but shows a slight improvement, although doubtful if it will be maintained. . (c.) This tree has the least infection, and shows a great improvement. This, however, is anything but conclusive, as other trees of the same sort untreated also have much less woolly aphis infection this season than might have been expected. ./ J. A. Campbell,-Orchard Instructor, Hastings.. No definite experiments were carried out by me last season when stationed in the Waikato, but I recommended several growers to treat affected trees with dressings of salt applied to the soil round the roots. No beneficial results were noticed by those who r tried the treatment. I know of some Jonathan apple-trees which are growing half in an asparagus-bed which is dressed each season with salt, but the trees, which are now about- five years old, were badly affected with the aphis last summer. J. H. Thorp, Orchard Instructor, Nelson. When stationed at Timaru I carried out experiments with salt on some very badly affected trees. - The treatment, however, was useless, the trees being simply white with aphis when examined at the end of the season. W. J. Courtier, Orchard Instructor, Canterbury District. I have given the salt method a trial by dressing the soil round the trees and lightly working it in, also by spraying with a strong solution when the trees were dormant. The result has not been very satisfactory, only a very slight, improvement being noticeable. ' E. A. Reid, Orchard Instructor, Christchurch City and Suburbs. Two six-year-old Dougherty trees badly infected with woolly aphis were selected and treated during the winter of 1911. A dressing of salt 2| lb. per tree was lightly worked into the soil during latter end of June. At. end .of July the trees were sprayed with salt solution, in the proportion of 15 lb. salt to 60 gallons water. When examined in March, 1912 (end of the season), the trees were a mass of woolly aphis, a marked contrast to trees of same age and variety growing in the same patch and treated with Montauk spray in July and infected parts painted with the undiluted solution during growing season. On these trees .it was a hard matter to find woolly aphis. These experiments showed that salt was quite useless in controlling the aphis. Waerenga Experimental Farm. . • The following trials were carried out on the 16th September, 1911: (1.) Four appletrees were sprayed with a solution of 5 lb. salt to 20 gallons water. (2.) Four trees were treated with salt as a fertilizer 3 lb. of salt per tree. (3.) Four trees were sprayed with the same solution as No. 1, and were treated with a root-dressing the same as No. 2. (4.) Three trees were left untreated. Up to the present time there is no visible difference in any of the trees. The aphis has not been checked in any way. Variety tested, Reinette du Canada. ■ Rualcura Experimental Farm. \ - Three experiments were carried out on the 15th September, 1911. The varieties of apples chosen for the expcrim nt were : Cox’s Orange Pippin, Byhill Pippin, Scarlet Pearmain, Rhodes Island Greening, Allington Pippin. In all cases trees of each were treated as follows : (a.) Sprayed, with a plain solution of salt in the proportion of 15 lb. to 50 gallons, (b ) Root-dressing of 3 lb. of salt per tree, (c.) Untreated. Neither of the treatments (a) and (b) gave any beneficial effects over (c). This applies to all varieties above mentioned. With the variety Cox’s Orange Pippin, trees that had received the root-dressing were worse with woolly aphis the following season than those trees left untreated. Tauranga Experimental Farm. About two dozen apple-trees were treated with salt, (a.) One-third of these had 41b. salt scattered round them within a circle cf 9 ft. (d.) Another third had the same amount of salt scattered around them, and also were sprayed with a solution of salt water, 1 lb. salt to 1 gallon of water, (c.). The other third were sprayed with the same salt and water, but had no salt round the trees. Results.— (a.) Did not seem to be any freer from disease than trees untreated. (6.) Appeared to be freer from aphis for a longer period than those only sprayed, (c.) These trees were freed from aphis, but it did not appear to kill the eggs, as they were again affected by the end of December.

Arataki Experimental Farm.

On the 9th September, 1911, fourteen rows of apples were treated with agricultural salt at the rate of 3 lb. per tree, each row having a check row of same variety untreated to determine results, which were as follows : The treatment had no effect on the few trees that were slightly attacked with woolly aphis, but the trees treated showed a better development of growth than those untreated. The soil round the treated trees also held the moisture up to the surface all through dry summer, and no doubt this accounted for the extra growth. Another point worthy of notice in this experiment is that the treated rows only had to be hoed round once at later end of season, the salt keeping the weeds in check, while those untreated had to be hoed round every two or three weeks.

Moumahaki Experimental Farm.

On the 19th September, 1912, a line of cordons, sixty-two in number, were selected, and of these fifty were sprayed with a solution of. salt, the balance, twelve trees, being unsprayed. The solution used was 2 lb. salt to 3 gallons of water. The fifty trees were also treated to a mulching of salt at the rate of 5 lb. to twelve trees. There is no apparent difference between the condition of those treated and the untreated ones. • ■ -j

Weraroa Experimental Farm.

Experiments were duly carried out in accordance with instructions. The spray was found to be more effective against the aphis than any; other spray used, but the same difficulty of reaching all the affection exists, and, though the work was carefully carried out, aphis soon showed on the trees. Further, this spray had not the slightest effect on scale, and would therefore be impracticable where both pests existed. The grounddressing had no effect on the aphis whatever, although the application was repeated at a- later date, about two months after the first.

Quantity. Variety. Date applied. Result. 4 lb. Whang ar ei. 1 Warren’s King .. 1 20/9/12 hangarei. 20/9/12 Nothing noticeable by way of iniNothing noticeable by way of ini6 lb. 1 20/9/12 provement. Ditto. 10 lb. Northern Wairoa. 1 Reinette du Canada 1 30/9/12 No improvement. 8 lb. 1 Ohinemuri 30/9/12 99 ’ .

Following are the results of experiment :-