398 INSECTICIDES, FUNGICIDES, AND WEED KILLERS. 



.ieprived of dilon)i)hyll. The sc.mU only 

 fjeriiiiuate in coiiUi't with tln' v.iits (if the 

 nurse plants. They plant tlnm^ h r^ thire, 

 and their root which is a nicri' ^in krr |Mue- 

 trates, whilst it ramifies as fur as t lie v.is nhir 

 l)unilles. These root suckers arc perennial if 

 the orobanehe is Hxed on a perennial plant, 

 anil the multiplication of this parasitic plant 

 may take place without the intervention of 

 its seed, lliis is especially the ease witli 

 the orobanehe of clover. 



Okyctes nasicornis. JViiiiocfrds.— The 

 larva of this lar{j;e insect rcsemliles an enor- 

 mous white-worm. Generally it lives almost 

 exclusively on decomposing vegetable matter, 

 in melon beds, and in dung in gardens. Per- 

 Toncito regards it as being the cause of 

 damages done in Italy to the roots of vines. 



Pk.\r Leaf Cluster Cups, see Gymnos- 



PORANGIDM SaBIN'.E. 



Pentatoma olerace.t; (cabbage bug). — 

 Green bug with red marks on the female, 

 white marks on the male, 6 millimetres long. 



Pextatoma ORNata (the decorated bug). 

 — Piebald bug, red and black, 1 centimetre 

 long. The female lays its eggs on the lower 

 surface of the leaves, they are placed so as 

 to form bauds. The larvae, like the adults, 

 .suck the juice of the leaves. 



Pent.\tomides (V)ugs).— Several species of 

 pentatomides, kiniwii viilu.irly as bugs, live at 

 the expense of the rruritiis. Owing to their 

 large number tin y iiniy r:inse great damage 

 in caljliage field< ii\' sik kin.; tlieiv juice. 



Pentodon ri \« rATr>. -'I'his mleoptera, 

 injurious to vines, II 1 1 I'll r,> -mljles thebousier. 

 Its larva, which when full ^rown is twice 

 the size of the white-worm, lives in the soil 

 to the detriment of the new plantations of 

 grafteil American vines, for which it has a 

 marked preference, of which it gnaws the 

 young wooil for two to three years. 



Peritelus griseus.— This little weevil 

 nightly attacks in hundreds the buds of the 

 vine anil fruit trees. It preferably hides 

 during the day in the buds or in the soil at 

 the foot of the vine. 



Peronospora (mildew and white rust). — 

 Fun'.'i of which the mycelium lives in the 

 interior of the tissues and which produce on 

 the surlace of the attacked organs whitish 

 tufts resembling blights. They are chiefly 

 distinguished by tlie fact that their mycelium 

 lives in the interior of the tissues whilst the 

 blights crawl on the surface nt the cir,i,'iuis 

 attacked. 



Peronospora arborescens (mildew of 

 the poppy). — It attacks the leaves and the 

 inflorescences and may cause great damage. 

 The conidiophora are on the lower part of 

 the organs attacked and form a white, tlien 

 yellow velvety coating. This Peronnspora 

 attacks different species of poppies. 



Peronospora gangijformis (lettuce mil- 

 dew).— The lettuce mildew does not attack 

 lettuces alone but different other com- 

 posite plants. It often attacks artichokes, 

 chicories, and cinerarias. There are annu- 

 ally grown by market gardeners (French) 

 about 2,000,000 lettuces, of which the Pero- 



/iiispimi i/itii'jh'nir/nis sometimes destroys a 

 third, it app-ars diiefly on the salads 

 forced in beds to sell as early vegetables. 

 The leaves are covered, especially l)elow, with 

 white efflorescences tbrnied by the conidio- 

 phora. The conidia germinate very easily, 

 without, however, forming zoospores hke the 

 Peniaiispora I'l'tim/a, by issuing directly a 

 germinative tube which penetrates the leaf 

 and creates in the cells a new mycelium. 

 The leaves invaded commence by yellowing, 

 they then dry or rot. In the atmosphere, 

 continually moist and warm, which reigns 

 under the frames, it will be seen that nothing 

 is opposed to the rapid progress of this dis- 

 ease, and that the ravages miy become con- 

 siderable. The organs of propagation from 

 one year to another are the oosjjores which 

 are formed in the debris of the dead leaves. 

 It is therefore necessary n^ver to thmw them 

 with the dung which will form the mould of 

 the following crop, but to destroy all the 

 diseased plants. To avoid invasion, it is 

 well to select new soil into which to trans- 

 plant the lettuce. 



Peronospora Schachtii (mildew of the 

 beet). — -Beet crops are sometimes ravaged 

 by beet mildew. The imrasitie fungus which 

 produced this disease |iirtei':ilily attai'ks the 

 young leaves, thus liemniin^' in many cases 

 one of the causes of the rot of the heart of 

 the beet. Amongst beets, the leaves of 

 which have been attacked, the amount of 

 sugar contained in the routs is always con- 

 siderably diminished. Like tii.il ni the mil- 

 dew of the vine tlie niyecliuiii ni /'•,,,,/, i-<j)iira 

 Srhrirhfif crawls between the eelU ,if the 

 plant aui] pushes the grey lilac eonilinphora 

 thniujli the st'iiiiata, especially to the lower 

 surfa-e nl llie leaves. Till- deta-heil ronidia 



geriniiiale ll-crly I 

 tion tlllie |)i.T.'e^ I 

 instal itselftllrre. 



are fm-ne'il in .int i 



This. Use;, sr is, til 



leaves (it (lis-asei 



ir :^'ernuna- 

 tlie leaf to 

 <(nosp(ires) 

 ke,| leaves. 

 fe-1 l,v the 

 le vear to 



another. When the disease exists in a field 

 the leaves must be destroyed and not carried 

 to the stable nor the dungliill. They are 

 buried on the spot. Rotations greatly j^re- 

 vent the spread of this disease by oospores. 



Peronospora Schleii>eni (mUdew of the 

 onion). — This mildew eauses -i-eat damage to 

 onion crops. In wi t weal In i it may assume 

 such an extension thai Ike whole of the 

 plant is invaded and all the .mions ])erish 

 rapidly. Like all Pi'mnns/iuni the mveclium 

 lives in the interior of the le,i\cs, espi'cially 

 the young ones, ami discharges enniiliophora 

 through tin' stoniata. The conidia winch 

 are detached therefrom are the organs of dis- 

 semination during summer, and the oospores 

 formed in the dead leaves transmit the dis- 

 ease from year to year. The stocks attacked 

 by this parasite have leaves with yellow zones 

 which wither ; the plants become yellow and 

 finally die. 



Peronospora trifouoru.m (mildew of 

 clover). — This fungus attacks clover, lucerne, 

 and a great many leguminous plants. When 



