Showing papers on "Infestation published in 1973"

The influence of nematodes on photosynthesis in tomato plants

Abstract: The rate of photosynthesis of tomato seedlings was measured for up to 22 days after heavy infestation with Meloidogyne javanica larvae. A decrease in photosynthesis compared with uninfested controls was detected within 2 days of invasion by the larvae, and this response was maintained throughout subsequent growth. During early stages of infestation the decreased photosynthesis was highly significant when expressed on the basis of fresh weight, leaf area or total chlorophyll content. It is suggested that this is a physiological response, perhaps resulting from reduced supply of root-derived factors which influence rate of photosynthesis. During later stages of the experiment the reduced rate of photosynthesis was at least partly due to the smaller size of infested plants.

The influence of wild and cultivatedGramineae andCyperaceae on populations of sugarcane borers and their parasites in North India

Abstract: Sugarcane borers frequently inhabit wild and semi-cultivated grasses growing in the proximity of cane fields. In India, in view of the year-round cultivation of sugarcane, wild grasses are not necessary for the perpetuation of borer species, but observations indicate that certain borer species migrate from wild or other cultivated grasses to cane, thereby increasing levels of infestation in cane during certain seasons. Parasitism of borer species when present in cane is compared with that in wild or other cultivated grasses.Telenomus spp. amongst egg parasites andApanteles flavipes amongst larval parasites are striking examples of parasites which show preference for the same borer species when they occur on wild hosts than on cane, as indicated by the degrees of parasitism.

Changes in growth regulator content of radish seedlings, Raphanus sativus, infested with the aphid Myzus persicae

Abstract: SUMMARY Following 10 days of infestation by the aphid Myzus persicae there was an increase in the amount of growth inhibiting substances and a decrease in cytokinins, gibberellins and auxins in infested as compared with similar uninfested radish seedlings. Even after previously infested seedlings have been freed of aphids for 10 days, differences in the hormone balance remained. The possible relationships between the changes in hormonal balance and the effect of the aphid infestation on growth, translocation and wilting are discussed.

Aster Leafhopper: Source of Infestation, Host Plant Preference, and Dispersal

Abstract: The local movement and host plants of Macrosteles fascifrons (Sta1) were studied for three years in eastern Washington by light trap surveys and sweeping. The data indicate that this leafhopper did not migrate from remote breeding areas, but populations arose each year from overwintering eggs laid on grain, clovers (red, ladino, and alsike), and grasses, and dispersed to vegetable crops such as carrots and potatoes when the grain and clovers matured or when they were unsuitable as food. The aster leafhopper returned to fall-planted grains and weed hosts in late summer for oviposition of overwintering eggs.

Evaluation of biological control of the oak leaf-miner Phyllonorycter messaniella (Zell.) (Lep., Gracillariidae) in New Zealand

Abstract: To evaluate the effectiveness of the introduced Hymenopterous parasites Apanteles circumscriptus (Nees) and Enaysma splendens Delucchi in the control of Phyllonorycter messaniella (Zell.) samples of leaves were taken from infested oaks during 1969–70. In Christchurch there were three generations of P. messaniella per year with spring, summer, and autumn emergence periods. Infestation on deciduous oaks was negligible in some areas but was 6.3 mines/leaf in the lower crown of oaks close to evergreen oaks on which P. messaniella overwinters. On deciduous oaks total parasitism ranged from 30% to 80%. Apanteles was the most abundant parasite but Enaysma assumed almost equal importance on oaks with low infestations. Pnigalio pectinicornis (L.), a self-introduced parasite, has been almost completely displaced by the other two parasites since their introduction in 1957. The infestation intensity recorded in Nelson (2.3 mines/leaf) was much lower than the level reported before the release of the parasites (40+ mines/leaf), but still much higher than levels in Europe.

Growth and wilting of radish seedlings, Raphanus sativus, infested with the aphid, Myzus persicae

Abstract: SUMMARY After 10 days of infestation by the aphid Myzus persicae growth of radish seedlings was reduced by 38 %, and the volume of sap bleeding from the stumps of cut stems of infested seedlings was 4% of that exuding from the stumps of uninfested seedlings of the same age. Diminished bleeding could not be accounted for by the 52 % reduction in the weight of the roots of infested seedlings. After 14 days of infestation, necrotic patches developed along the veins of the cotyledons which yellowed noticeably. If freed of aphids the seedlings subsequently resumed growth and their was an increase in the volume of bleeding sap produced by their cut stems. Symptoms associated with aphid infestation cannot be attributed either to virus disease or initially to exhaustion of the seedling's carbohydrate and nitrogen reserves. Possible causes of the symptoms described are discussed.

Observations on Saddle Gall Midge (Haplodiplosis equestris (Wagn.)) in Eastern England

Abstract: SUMMARY Data comparing the amount of infestation in eastern England on wheat, barley and oats by saddle gall midge are given for the years from 1967 to 1972. The level of infestation decreased in 1971 and 1972. The changes in the numbers of overwintering larvae in several fields, with their cropping, are recorded. In 1971 and 1972 the first adult was trapped on 18 and 19 May respectively; the peak flights occurred on 31 May 1971 and on 11 June 1972. It was not possible to obtain an overall relationship between the amount of galling and yield. It is suggested that the individual effects of the many factors which can affect yield can only be assessed from detailed experiments. In a small-scale trial in 1972, a fenitrothion spray applied in June prevented galling of barley.

Seasonal Abundance of Heliothis larvae on Cotton in the Presidio, Texas, Area

Abstract: Both the bollworm, Heliothis zea (Boddie), and the tobacco budworm, H. virescens (F.), are very important pests of cotton in the Presidio, Tex., area. Infestation levels often require an extensive insecticidal spray program over most of the cotton produced in the area.

Phosphorus Compounds as a Cause of an Increase in Numbers of the Flat Mite

Abstract: Oil sprays as well as fumigation with hydrocyanic gas have long been used as the common means of control against scale insects on different species of citrus trees in Egypt. Applications are usually carried out late fall and winter. During the last few years some phosphorus compounds applied in summer were used for the same reason. Meanwhile it was noticed that infestation with citrus mites, especial­ly the flat mite Brevipalpus californicus, has recently increased, a matter causing many shipments of citrus fruits to be rejected for export due to the infestation sym­ptoms. Phosphorus compounds have been reported as a cause of an increase in te­tranychid mites and of populations of aphid and white flies. The following experi­ment was undertaken to investigate the effort of some phosphorus compounds, in­cluding those recommended, against citrus scale insects, on the flat mite popula­tion in comparison with certain acaricides known. to be effective against this mite.

Evaluation of mountain pine beetle infestations, Yellowstone National Park, Wyoming, 1972

Abstract: The mountain pine beetle, Dendroctonus ponderosae Hopk., infestation advanced north and eastward from the 1971 infestation boundary in Yellowstone National Park. Infested trees were found in Indian Creek Campground at the north end of the park and around the north end of Yellowstone Lake. A ground survey showed an average of 15.5 infested trees per acre. A decrease in number of infested trees occurred in older infestation centers in the southwest corner of the park. The infestation will continue at epidemic status in areas containing susceptible stands.