278 



the time of the last picking. Cotton seed (other than that for sowing) 

 and seed cotton stored after the middle of January should be kept in 

 moth-proof stores, and cotton seed intended for sowing should be 

 fumigated or treated by heat before distribution. All other seed 

 should be crushed or exported before 1st April, unless treated in a 

 similar way. 



Jack (R. W.). Rhodesian Citrus 1?ests.— Rhodesia Agric. Jl, Salisbury, 

 xiii, no. 2, April 1916, pp. 215-233, 6 plates. 



Aphis tavaresi (black orange aphis) is generally distributed 

 throughout South Africa and attacks young citrus trees especially 

 ditring the spring months before the rains. Reproduction during the 

 warm season is mainly parthenogenetic. Both winged and wingless 

 females occur and the young produced are capable of parthenogenetic 

 reproduction within a few days. The natural enemies include several 

 Coccinelhds, of which Chilomenes lunata is the commonest, Syrphid 

 larvae, lacewing flies and Hymenopterous parasites. Chmatic con- 

 ditions probably form the most effective natural check on these insects. 

 The best artificial method of control is the use of a contact insecticide, 

 such as dilute paraffin emulsion, resin wash, nicotine solution, etc. 

 A species of Trioza occurs in several widely separated locahties in 

 Southern Rhodesia. It attacks the young f oUage of all varieties of citrus, 

 causing a characteristic wrinkled appearance. An internal parasite 

 has been detected in insects obtained in Umtah, and in Cape Colony a 

 Syrphid enemy has been recorded. Remedial measures include hand- 

 picking or spraying with washes used against scale-insects. In addition 

 to C. lunata, Aphids and scale-insects in Rhodesia are attacked by the 

 following Coccinelhds :• — Noviu^ cardinalis, Aulis foedata, Chilocorus 

 distigma, Exochomus auritus, Lotis neglecta and Alesia hohemani. 

 Papilio demodocus (citrus butterfly) sometimes causes defohation of 

 young trees, but as a rule is not a serious pest. The larvae can be 

 controlled by hand-picking, while the adults, which are attracted to 

 beds of bright flowers, can be captured in such situations. Argyroploce 

 leucotreta (citrus codling moth) is sometimes abundant in neglected 

 orchards, where as much as 70 per cent, of the fruit may be rendered 

 useless. The eggs are laid singly on the fruit. The larva, upon 

 hatching, bores into the pulp, emerging only to pupate in the soil. 

 The duration of the developmental periods in acorns in South Africa 

 is as follows : — Egg-stage, from 9 to 10 days ; larval stage, from 84 

 to 90 days; pupal stage, from 14 to 18 days ; there are probably three 

 generations during the year. On citrus fruits the larval stage is prob- 

 ably shorter. There are no definite broods in Rhodesia, adults having 

 been bred during every month, except December. Infested fruit 

 ripens prematurely and falls from the tree. Injury also allows the 

 entrance of moulds and bacteria which hasten decay. This species 

 has been bred from orange, naartje, lemon, guava and pomegranate 

 and also from the wild fruits of Zizyphus mucronatus and Sclerocarya 

 caffra. In South Africa additional hosts are acorns, apricots, peaches, 

 plums and the wild plum. Repressive measures include the 

 destruction of infested fruit, the ehmination of alternative hosts and 

 the discontinuance of the production of citrus fruits out of season. 

 Three species of fruit-piercing moths, namely, Oihreis materna, 



