548 



Garden and Forest. 



[November 12, 1890. 



The Black Peach Aphis. 



Tj*OR many years Peach-trees in New Jersey, especially those 

 -^ in the sandy districts, have been in an unhealthy, thriftless 

 condition. "They are badly dwarfed, and make only a feeble, 

 sickly growth. The leaves are light green or yellowish, more 

 or less rolled at the margins, and red or purple spotted from 

 the attacks of Fungi." The trouble is not caused by the yel- 

 lows, nor does it seem to be due to a particular fungoid 

 disease. Fertilizers have been used to stimulate the trees, and 

 kainit of potash has gradually come to be looked upon as a 

 specific. This substance is undoubtedly a valuable stimulant 

 and fertilizer, but it has another quality, to which, in the light of 

 recent developments, most of its success is probably due. It 

 is an insecticide of no mean value, and to this quality it owes 

 the specific effect in a majority of cases. Dr. E. F. Smith, who 

 has for many years studied the diseases of the Peach, has 

 found that a plant-louse attacks the roots of the trees, and so 

 devitalizes them as to check growth and give the well known 

 yellow appearance. 



This aphid {Aphis Persicce niger, E. F. Smith) was very 

 abundant in New Jersey during the season of 1890, not only 

 on the roots, but on the leaves. During the month of May, 

 at Vineland, the young shoots of several Peach-trees were 

 attacked so that they were curled and dwarfed and all 

 but destroyed. There was a similar experience in other 



some curious differences. The antennas in many of the 

 plant-lice are furnished with sensory organs, the exact use of 

 which is still unknown. In this species these sensory pits are 

 most remarkably developed ; not only are they very numer- 

 ous, but they are on every joint, and are also very large. 

 The figure brings out the structure fairly well. 



Fig. 70. — Peach Aphid {Aphis Persicce niger) ; Winged Viviparous Female. 



localities. The forms of this insect seen on the leaves and 

 branches are principally wingless, viviparous females, deep 

 black and shining, smooth, with a well marked margin or se- 

 ries of lateral depressions on the abdomen. The young are 

 paler, more brown in color, and sometimes with a green shade 

 in newly born individuals. Among these are found a few 

 winged forms, of which the annexed figure gives a fair 

 idea. 



They are of the same shining black color as are the wingless 

 forms, but the body is not so stout and the antennae are longer. 

 It is by these winged forms that the species is distributed. 

 They fly to neighboring orchards, especially favoring young 

 or nursery trees, and plant colonies which rapidly increase ; 

 and about midsummer make their way into the ground. At 

 this time the leaves are comparatively deserted, but the roots 

 are swarming with wingless forms. Nursery-trees now begin 

 to sicken, and many die off. Dr. Smith mentions several cases 

 of thousands of trees entirely killed, while one instance at least 

 has come under my own notice in which the seedlings were 

 rapidly succumbing to the attacks of this insect. Other failures 

 reported to me are almost certainly referable to the same 

 cause. On the root system the development continues, only 

 wingless forms being produced, and this goes on until winter. 

 In the mild winter of 1889-90 they continued nearly through 

 the season. In the spring they come to the surface, and the 

 life cycle begins afresh. There seems no place in this exist- 

 ence for the egg state, and true, sexed individuals are not 

 known. There seems to be a continuous, agamic reproduc- 

 tion. 



In general appearance this Peach-louse is very like the spe- 

 cies infesting the Cherry {Myzus cerasi, Fabr.) ; but there are 



Antennal Joints of Peach Aphid. 



a, antenna of young louse ; i, first long joint of winged form ; c, second 

 long joint; d, third long joint; e, whip joint; f, sensory pit from top ; 

 g, same from side. 



In the Cherry-louse these sensory pits, though still of good 

 size, are very much reduced in number, and they are entirely 

 wanting on the second long joint. On the third joint there 

 is but a single pit near the tip, 

 and only on the whip joint are the 

 two species at all alike. Another 

 curious fact in these antennas is, 

 that the joints are imbricated, or 

 with scale-like markings, as rather 

 roughly indicated in the figures. 

 The injury is done by sucking the 

 sap of the tree and thus diverting 

 the nourishment. 



While the insects are above ground 

 they are quite readily dealt with. The 

 ordinary whale-oil soap — Leggett's 

 Anchor Brand — is as good a remedy 

 as any; it should be used at the rate 

 of one pound in six gallons of water; 

 this will kill the lice without injury 

 to the foliage. 



This insect in its underground 

 state is the most destructive and the 

 most difficult to deal with, as it 

 cannot be treated with insecticides. 

 The kerosene oil emulsion might 

 reach it, but it would have to be 

 very thoroughly applied. We have 

 a much better remedy in the potash 

 salts, and of these the kainit is best, 

 perhaps because it contains more 

 salt than the muriate. This has the 

 advantage of being stimulant as well 

 as insecticide, and the entire cost of 

 the application is retained in the 

 vigor of 'the tree. The insecticide 

 is therefore "thrown in," for only 

 the fertilizer is paid for. The salt's 

 should be scattered broadcast, in good 

 fertilizing quantity, and preferably 

 before a rain, so that the salt water may reach the roots in 

 the quickest possible time. Never hill up the trees with 

 potash. The chances are that by doing so you will kill the 

 trees as well as the insects. 



Rutgers College. John B. Smith, 



^iX ^Z> 



Fig. 72. — Antennal Joints 



of Cherry Aphid. 



[Myzus cerasi, Fabr.) 



a, first long joint ; b, third 

 long joint ; c, whip joint ; all 

 of the winged viviparous 

 female. 



