440 MAIZE 



CHAP, cutworm. Mr. Mally finds that two distinct insects with 

 similar habits are known by the name stalk-borer, one of 

 which is the larva of the moth Sesamia fusca Hampson (Fig. 

 165) which was ably described by Mr. Mally and beautifully 

 illustrated by Mr. McManus, in the Cape Agricultural Journal, 

 August, 1905, pages 159-68. This pest is well known to all 

 South African maize-growers, and is responsible for the loss of 

 anywhere from 25 to over 50 per cent of the maize crop, ac- 

 cording to estimates made by Mr. Mally and Mr. Claude Fuller. 



According to Mr. Mally the first evidence of the presence 

 of the borers is the withering of the top of the young plant, 

 which turns a brownish-red colour, as if scorched, due to the 

 fact that the centre or " heart " has been eaten away. Although 

 the centre of the plant has been destroyed, the outer leaves and 

 roots do not always perish, but make an effort to recover. The 

 leaves may become somewhat darker than in surrounding plants 

 and in some cases "suckers" are thrown out later, so that in 

 time the plant fills its place in the field. All such plants must 

 be counted as loss, for they seldom or never produce ears ; their 

 only value is for ensiling or for feeding to stock as green fodder. 

 The second brood of stalk-borers does not exert such a decided 

 influence, because the plant is then strong enough to resist the 

 attack, for the burrows of the insect (Fig. 165, 3) are not suf- 

 ficiently large to prevent the flow of sap. 



405. Life History of the Stalk-borer. — There are two 

 broods of Sesamia fusca and three of the other species of stalk- 

 borer, during the season. The last brood passes the winter as 

 larvae within the stalks or in the cob, and in late-harvested 

 ears they are often found wrapped up between the husk and 

 the ear. These larvae pupate and then change into moths, 

 which emerge between October and December. If maize plants 

 are available, the female moths begin to lay their eggs almost 

 immediately, but always at night, hiding during the day. These 

 eggs are deposited in clusters under the edges of the leaf- 

 sheaths, and hence are protected from destroying agents ; they 

 are faintly visible through the sheaths, and vary in number 

 from 5 or 10 to over 100. The eggs hatch in seven to nine 

 days. The young larvae begin feeding on the maize-stalk at 

 once, quickly eating their way towards the centre; "they are 

 very careful to remain under the sheath all the while, and it 



