Peach Aphid Research Articles

Magnesium silicate in virus transmission

Magnesium trisilicate (Mg 2Si 3O 8·5H 2O, here abbreviated as MgSi) functioned as an abrasive in the transmission of cucumber mosaic virus (CMV) and all viruses tested, but as an abrasive it was only about one-sixtieth as effective as Celite. When variable amounts of MgSi were added to inoculum of CMV from cucumber and containing Celite, the increase in infection due to MgSi was about 2-fold; but when beet, carnation, pine, or oak leaves, ribonuclease, or peach aphids were added, the increase in infection due to MgSi was up to 52-fold. Transfer of CMV from beet to cowpea with Celite as abrasive gave very low infection, but addition of MgSi increased infection about 20-fold. This MgSi effect was increased to 78-fold by sucrose and 93-fold by K 2HPO 4. MgSi, in the presence of Celite, increased transmission in 8 of 16 virus host combinations tested and therefore has wide application. The greatest increase in transmission (231-fold) was in the transfer of tobacco mosaic virus (TMV) from beet to bean. The greatest decrease in transmission (140-fold) was in the transmission of tomato ringspot virus (TRSV) from cucumber to cucumber. The presence of MgSi in the inoculum increased the size of CMV lesions in cowpea. It is believed that the major merit of MgSi in virus transmission is as a neutralizer of inhibitors, although MgSi may itself function as an inhibitor.

Trioxys similis n. sp. (Hym. Braconidae, Aphidiinae), eine neue Blattlaus-Schlupfwespe aus Frankreich

In the present paper the author describes the new speciesTrioxys (Trioxys) similis n. sp. (Hymenoptera: Braconidae, Aphidiinae), which has been reared in France from the peach aphid, presumablyMyzus persicae (Sulzer 1776). Considering the fact that this aphid is a world wide distributed pest causing heavy damages by transmission of numerous plant viruses, attention is drawn to use this braconid parasite as a limiting factor in biological control.Trioxys similis n. sp. belongs to the group of species “Trioxys angelicae (Hal. 1833) s. l.”, the biology and taxonomy of which is briefly discussed. The existence of various strains of one parasite species, differing only in their host range or host preference is a major problem both of applied entomology and of insect taxonomy. It is suggested to name these morphologically indistinguishable forms according to terms used in microbiological nomenclature.

Seasonal Fluctuations of the Green Peach and Turnip Aphids on Commercial Greens Crops in Oklahoma1

Seasonal Fluctuations of the Green Peach and Turnip Aphids on Commercial Greens Crops in Oklahoma1

The relation between the infection of potato virus disease and seasonal variation of aphids population in the warmer region of Japan, with special reference to the translocation of virus poison.

In order to know the interrelation between the infection of potato virus disease and the seasonal variation of aphid population, investigations were carried out on the Chugoku branch farm in three successive years from 1946 to 1948. The results of the study are summarized as follows:- 1. In Himeji district, the peach aphid (Myzus persicae Sulzer) and Cotton aphid (Aphis gossypii Glover) are the main species attacking the potato. As to the ecological type, apeterous female predominated in all three years, throughout the potato season. 2. The infestation of aphids on potato plants generally began at about the end of April, just after the potato sprouted ; a month later, at about blossoming time of potatoes it reached the maximum, and at about the middle of June, it terminated. In the fall crop, the infestation began early in October and ended by the end of the 10th of December, and generally speaking more aphids were observed on potatoes in fall than in spring. Some differences, however, were observed during the three years. These appeared to be due mainly to the difference in growth as a result of growing conditions. 3. The rate of increase in virus infection is closely connected with the number of aphids. It was also confirmed that from 20 to 30 days were necessary for the virus poison introduced by viruliferous aphids to be translocated from leaves to tubers. 4. The above mentioned fact offers the foundation in determining the date of harvesting in order to secure disease free seed tubers in the warmer region ; i.e. if seed potatoes were dug up in spring within some 20 days after the maximum infestation of aphids, we can safely say that they are practically virus free. 5. In fall crop, notwithstanding the more infestation of aphids than in spring, there was no significant increase of virsu, indicating the importance of fall crop for the production of seed potatoes.

Resistance of potato seedling varieties to the natural spread of leaf roll

Potato seedlings were exposed to field spread of leaf roll from adjacent rows in an area where leaf roll spreads consistently year after year. Parents used at first included commercial American and European varieties reputed to be resistant to leaf roll, and a few of the crosses contained some seedlings resistant to the natural spread of leaf roll. When these resistant seedlings were used as parents, the resulting crosses generally were more resistant to field spread than crosses of other kinds. Greater resistance in one of the parents did not always mean greater resistance in the cross. Greater resistance in a cross (on the basis of percentage of seedlings showing any leaf roll) was not necessarily correlated with the percentage of total plants showing leaf roll in the infected seedlings. Field resistance in given seedlings and varieties varied from one season to another on the same farm. Although green peach or spinach aphids (Myzus persicae) probably are an important factor in the field spread of leaf roll, aphid resistance in seedlings is not necessary for field resistance to leaf roll. It is possible to combine field resistance to leaf roll with many characteristics considered commercially desirable in this country.

Some properties of the curly-top virus

Abstract does not appear. First page follows. According to some plant pathologists the virus diseases of plants are divided into two groups, the mosaic and the yellows diseases. The mosaic diseases under optimum conditions cause a mottling of the leaves, usually in the growing tissues of the plants. Some of the mosaic diseases are highly infectious, while others are not, and some have not been transmitted mechanically. Some of the mosaic viruses have been shown to be filterable, but others are not. Intracellular, cell inclusions, or x-bodiesare associated with many diseases of this group. Mosaic viruses are transmitted mostly by sucking insects, usually aphids, rarely by chewing insects. Some single species of aphids are associated with the dissemination of many separate mosaic viruses, other species with the spread of but one mosaic virus. The peach aphid (Myzus persicae) is associated with the dissemination of fourteen separate virus diseases, and the potato aphid (Macrosiphum solaniiolii) is associated with the spread of six plant viruses. (57) Some insects are mechanical vectors of mosaic viruses, as in the case of cucumber mosaic, (15) and retain the virus for only a short time. The aphid vector of spinach blight retains the infective power for a period of five days. (38) Some mosaic diseases are transmitted through the seeds.