395 



Dry (F. W). Flax Caterpillars in Kenya Colony, with special reference 

 to the Limitations of the Roping Method of combating them. — 



Bull. Ent. Res., London, xii, pt. 1, June 1921, pp. 99-102. 



Caterpillars on flax are serious pests in Kenya Colony. They belong 

 to more than one species, the most common being Phytometra orichalcea, 

 F. ; Heliothis obsoleta, F., is also met with. They have a wide range 

 of food-plants, including beans, potatoes and rape. Serious damage 

 to flax was reported in 1918, 1919 and particularly 1920. In its 

 early stages the crop may be completely consumed. In the later 

 stages the seed-bolls are especially attacked. When the caterpillars 

 are less numerous, the growing point of the plant is often damaged 

 at the apex. Most of the damage is done from May to August, 

 following the long rains, but outbreaks have occurred after the short 

 rains, which are due from October to December. The life-cycle of 

 P. orichalcea occupies about 12 weeks. Eggs are laid two days 

 after the emergence of the moths and hatch in about 10 days. Forty- 

 one days are spent as a larva and 30 days in the cocoon. 



Eight species of parasites, both Hymenopterous and Dipterous, 

 have been reared from this moth. 



Spraying is not very effective, though in one case some success was 

 obtained with strong Paris green against small caterpillars. Control 

 by means of roping [R.A.E.,K, viii, 432] has been attempted by several 

 flax-growers, but accounts of the success obtained were conflicting, 

 and a number of experiments were undertaken to test the efficacy of 

 this method. The' conditions involved in success or failure seemed to 

 be the kind of rope, the frequency of roping and the size and number 

 of the caterpillars. A heavy rope has more effect than a light one. 

 On small caterpillars the effect is both direct, by injury, and indirect, 

 by placing them at the mercy of ants. On large ones there is little 

 effect by either means. If the caterpillars are very numerous, 

 roping would probably have to be clone more often than is feasible. 

 Very little success has been reported against bad outbreaks, and it 

 appears that roping produces its effect by bringing about the death of 

 only a small percentage of caterpillars each time the rope passes. Thus, 

 though roping will be successful in favourable circumstances, it will 

 probably be replaced by something more effective in the future. 



Dry (F. W.). The Red Scale, Chrysomphaliis aurantii, Mask., in 

 Kenya Colony. — Bull. Ent. Res., London, xii, pt. 1, June 1921, 

 pp. 103-104. 



The eradication of Chrysomphalus aurantii. Mask, (red scale) in 

 Kenya Colony has proved impracticable. The life-cycle occupies a 

 total of 120 days ; larvae placed on plants in November moulted 

 for the first time after 18 days, the females moulted again after 50 daj's, 

 the first males emerged on the 65th day, and the first larvae of the 

 next generation were observed after 110 days. The average daily 

 temperatures during this time showed a minimum of 54 • 5° F. and a 

 maximum of 80-5° F. Contrary to expectation, coffee appears to be 

 immvme to the attacks of this scale, but, besides Citrus, it has been 

 found on rose, apple, plum and sisal. 



Selenaspidus articulatus, Morg. (West Indian red scale) has frequently 

 been mistaken for C. aurantii. It occurs both on Citrus dind coffee, but 

 is apparently not of any great economic importance. 



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