CIRCULAR WHITE PATCH IN TOMATOES.

New Zealand Journal of Agriculture, Volume XII, Issue 5, 20 May 1916, Page 388

CIRCULAR WHITE PATCH IN TOMATOES.

In the March issue of the Journal (page 200) a description and illustration were given of a somewhat common affection of tomatoes designated “ circular white patch.” Weather-conditions, and especially excessive sun-heat, were the reasons given for the appearance of this trouble, and correspondence was invited from any growers who had had any experience of the disorder. In response several letters have been received containing useful corroborative observations on this subject. Mr. H. J. Fowler, of Marton,, states that he is of opinion that the trouble is due solely to the scorching effects of the sun, because it is always seen on the sunny side of the rows and upon the same side of the fruit; also because the affected fruits on trained plants are generally upon the lowest trusses, which are subjected not only to the direct rays but also more especially to reflected heat from the ground. When the affection occurs higher up it was noted that the damage was probably originated by the separation in such fruit of the pulp and seeds from the casing, leaving a hollow, and thus preventing the inner part from exerting its cooling effects on the outer. Mr. ■ L. Shearman, Christchurch, writes that he is perfectly sure the affection is sun-scald, because the patches are always on the upper surfaces facing the sun—never underneath or on .the shady side of the rows. After a glaring hot day, and after the plants have been severely pruned, affected fruits were found along the exposed sides of pathways and along the eaves of the houses close to the glass. As a preventive he lightly sprayed the roof with whitewash, after which there was no further damage. When tender fruits were exposed to the full glare of the sun by picking and by the removal of the previously sheltering leaves, the injury in question was observed.

Mr. Christie, Burnside, has come to the conclusion that the affection is caused entirely by excessive heat. He has witnessed similar appearances upon apples and potatoes exposed to the sun.

Mr. W. J. Best, Auckland, says that he concludes the trouble is sunburn. He took healthy green fruits from different plants, exposed them to the sun in January, and produced the same effect.A. Waters, Biological Assistant. . ■ .