492 



unsafe to use on the foliage of stone fruits except under favourable 

 weather conditions, damp weather causing decomposition of the 

 arsenate. The basic type of lead arsenate, usually labelled " tri- 

 plumbic " or " neutral " is a safer arsenical to use on these fruit trees, 

 as it is not decomposed by unfavourable weather conditions. It is, 

 however, a slower poison than the acid type and would not be as 

 effective unless applied when the canlver worms are very young. 

 Banding the trees with tanglefoot is also recommended for combating 

 both the spring [Palaeacrita rernata] and the autumn species 

 [Also])JnIa j^omeiaria]. 



BoxcQUET (P. A.) k Stahl (C. F.). Wild Vegetation as a Source of 

 Curly-Top Infection of Sugar Beets. — Jl. Econ. Enfom., Con- 

 cord, N.H., X, no. 4, August 1917, pp. 392-397, 2 plates. 



The identity of the specific organism responsible for the curly-top 

 condition of sugar beets has long been an unsolved problem. It was 

 known that the Jassid leaf-hopper, EuteUix tenella, Baker, played 

 some part in the dissemination of the virus, and experiment showed 

 that a single leaf-hopper in any stage was capable of producing the 

 curly-top condition by feeding on a healthy beet for two minutes. 

 Insects reared from the egg on healthy beets were unable to produce 

 the characteristic condition ; the ability to cause the symptoms was 

 accjuired only by feeding on affected beets, and this ability was lost in 

 from 15 to 35 days, if the insects were transferred daily to healthy 

 beets. A period of incubation, dependent on temperature and lasting 

 at least two days, was recjuired. The spasmodic occurrence of curly-top 

 outbreaks in isolated desert regions, where beets had never before 

 been gio\m, suggested that the virulent factor resided in food-plants 

 other than beet and was perpetuated by these plants. Recent 

 investigation and experiment have shown that Malva rotundifolia 

 (mallow), which is a common weed in beet fields, is at least a symbiotic 

 host of the virulent factor of curly-top in sugar beets. 



Tucker (E. S.). Relation of the Common Root Maggot {Pegomyia 

 fusckeps, Zett.) to certain Crops in Louisiana.— J^. Econ. Entom., 

 Concord, N.H., x, no. 4, pp. 397-106. 



CJwrfophila {Pegomyia) fiisciceps, Zett., was first found injuring the 

 stems of young tomato plants in 1914, the larvae piercing the stems 

 and burrowing in them until the plant was too weakened to stand 

 upright. A great many tomato plants were destroyed as a result of 

 this damage. Garden peas were also attacked, but seemed able to 

 "\\nthstand the injuries. Seed potato tubers were found badly infested 

 M-ith the maggots, and this was explained by the fact that the ground 

 had been prepared for the potatoes by a fertiliser composed of decaying 

 cotton seed, which in all probability was infested before use. Young 

 maize and onions have also been attacked. 



In the case of tomato plants, tobacco powder scattered on the beds 

 was a promising method of control and this material is said to act as 

 a fertiliser as well as being a repellent. The use of a trade preparation 

 called Pyrox seemed to afford almost complete protection to the 

 growth. The seed potatoes might have been protected by spraying 



