53G 



application of remedial measures have now succeeded in checking the 

 pests to such an extent that the fruit industry is again rapidly 

 developing. 



It is obvious that the introduction of the natural enemies of imported 

 pests from their original habitat would be an invaluable factor in the 

 control of injurious species, perhaps more so than in their native 

 country where they themselves are subject to controlling influences. 

 When a phytophagous insect attacks one species of plant more than 

 another, efficient results may be obtained by a thorough system of 

 crop rotation, while attention should be paid at the same time to 

 places suitable for hibernation, such as the rank grass usually fringing 

 cultivated fields. In this way, by breaking the continuity of the 

 food-supply, the life-cycle of the insect is interrupted, and the 

 removal of hibernation quarters will destroy a large proportion of the 

 over- wintering stages, with a consec^uent reduction of the spring brood. 



Jack (R. W.). Cutworms. — Rhodesia Ag-ric. Jl., Salisbury, xv, nos. 3-4. 

 June-August 1918, pp. 225-237 ; 344-348, 2 plates, 1 fig. 



Cutworms constitute one of the most destructive plant pests in 

 Southern Rhodesia on account of the variety of crops they damage. 

 They are frequently confused with Elaterids (wireworms), of which 

 the most familiar in Southern Rhodesia are Psaniniodes spp., which 

 live in the ground and feed upon the underground portions of plants, 

 being particularly injurious to tobacco, and with white grubs 

 [Lamellicorn larvae] which feed upon the roots of maize, small 

 cereals and grasses. 



Four species of cutworms have been recorded in southern Rhodesia. 

 Euxoa segehmi is the commonest and is well-known in Europe ; 

 E. longidentifera, Hmps., is a purely African species, only found in 

 company with E. segelum, and has not as yet proved very dangerous ; 

 E. spinifera, Hb., extends from southern Europe to the Cape and 

 India. It is scarcely considered a pest in Rhodesia and is usually 

 found in company with E. segelum. Agrotis ypsilon, Rott. , sometimes 

 occurrs in overwhelming numbers, but is sporadic in its outbreaks. 

 The adults of all these species are nocturnal and lie hidden in sheltered 

 places during the day. Oviposition begins about four days after 

 emergence, the eggs being laid among low-growing vegetation, attached 

 to the stems of plants, to stones, lumps of earth, etc. As many as 

 1,766 eggs were laid by a single female of E. segelum in confinement. 

 There are six larval instars ; the young cutworms feed chiefly upon 

 leaves and other soft tissue within their reach, keeping mainly under 

 shelter during the dayhght ; later they develop the habit of burying 

 themselves in the soil during the day, and feeding at night. The 

 chief damage is done by eating tlirough the stems of plants at the 

 ground level. The larval period, under summer conditions with 

 unlimited food, lasts about 29 days, the average time being a few 

 days longer ; in cold weather the growth may occupy several months. 

 In temperate climates attacks on young crops in the spring are due 

 to cutworms that have hibernated in a partly developed condition, 

 the low temperatures having suspended the vital processes in the 

 caterpillars so as to prevent starvation. In Rhodesia starvation 

 supervenes very quickly during winter if no food is available and the 



