Departmental activities. 303 



Tomato Erinose. — This is a disease of the tomato plant often 

 mistaken for an attack of mildew. In bad cases of attack the stems 

 and leaves, and even parts of the green fruits, become covered with 

 white patches, and before long the plant is seen to be thoroughly 

 diseased and collapses more or less rapidly. The mildewed-like 

 appearance is due to abnormal growth of plant hairs, and this again 

 is due to the presence of a multitude of minute mites, which shelter in 

 the protection of the hairs and can only be detected with a microscope. 

 Tomato erinose usually starts in a small way as whitish patches on 

 the main stems, but, as the mites breed with great rapidity, it does 

 not take long for them to spread over the greater part of the plant, 

 carrying destruction with them. Badly diseased plants may not die 

 outright, but linger on in a withered, useless condition for quite 

 a while. 



This seems to be a summer trouble and to be more in evidence 

 from the middle of summer onwards. It is reasonably supposed to be 

 the main cause leading to the failure of summer crops of tomatoes in 

 some parts where winter crops are quite successfully grown. 



It has not yet been found possible to conduct experiments for its 

 control, but the application of nicotine extract or greatly diluted lime 

 sulphur, in the early stages of the disease, may arrest its progress. 



Potato-stem Borer. — -A new pest in the shape of a potato-stem 

 borer from Lyndhurst, near Johannesburg, has recently come under 

 notice. This is the larva of a moth (Euzophera villora) which bores 

 in the stems and tubers, riddling them with galleries. It belongs to 

 a genus with several species of a harmful nature. One (E. osseatella) 

 has been reported as a potato-stem borer in Egypt; a second {E, 

 aglaeella) as a borer and girdler of walnuts in the United States ; a 

 third {E. semiftimeralis) as a borer in plums in the United States 

 and Canada. 



Borer in Wheat. — When at Selborne, Sundays River Valley, 

 in November last. Entomologist Gunn found a considerable 

 amount of damage being done to wheat by a moth larva somewhat 

 like the maize-stalk borer, but smaller. The borers were in different 

 stages of development and located in the internodes. All the infested 

 plants were found to ripen prematurely, but the grain, although 

 yellow, remained quite soft. Similar borers were also found in 

 barley and oats. The moths bred at Port Elizabeth from these borers 

 have been identified as Sesamia calamistris, Hmpsn. This insect is 

 believed by Senior Entomologist Mally to be the same as that observed 

 by him throughout the coast-belt, especially at Alexandria, 1908. It 

 has been reported as attacking maize in Zanzibar and Southern 

 Nigeria. 



Tobacco Slug at Middelhurg, Transvaal. — The tobacco slug 

 {Lema hilineata) has already been the subject of several notices in 

 the Journal. Its presence at Middelburg, Transvaal, is now to be 

 recorded. Writing to the Division under date of the 20th January, 

 1920, Mr. L. Watermeyer stated he had that day seen for the first 

 time at his farm, Hammarkop, insects on his tobacco plants which he 

 took to be the same as those described in the Journal for January. 

 Later, Mr. Watermeyer was good enough to send the Division 

 specimens confirming his observation. 



