Infestation

About: Infestation is a research topic. Over the lifetime, 8308 publications have been published within this topic receiving 82305 citations.

Metabolic changes in the rice plant during infestation by the brown planthopper, Nilaparvata lugens stal (Hemiptera: Delphacidae)

Abstract: The brown planthopper IViloparuata tugens is a serious pest in Asia. It darnages the rice plant by sucking the plant sap and by transmitting the grassy stunt virus disease. Apparently the heavy tlllering and shortstatured rice varieties grown with high rates of nitrogen fertilizer favor the population build-up of this species. Censequently its relative importance has increased during the past few years. In a greenhouse experiment at the International Rice Research Institute (IRRI), IR9-60 rice plants infested at 25 and at 50 days after transplanting with 400 newly hatched brown planthopper nymphs wilted and completely dried up in 3 and in 15 days, respectively(PATHAK, 1969). Such damage te the plants is termed \"hopperburn\". Lower insect populations caused reduced tillering, reduced crop vigor, fewer panicles, and higher percentage of unfiIIed grains (BALE and PATHAK, 1970). Basic infbrmation as te how the brown planthopper causes the browning and wilting of the rice plant, the typical characteristics of hopperburn, is still speculative, However, SoGAwA (I971) fbund a progressive decrcase in total protein and an increase in free amino acids, particularly arginine, asparagine, and glutamine in leaf blacles from feeding rice plants to the brown planthopper, Some possible causes ofhopperburn produced by ether species of sucking insects on their host plants have been reported, however. Studies in potato, for instance, showed that mechanical plugging of the xylem and phloem vessels of the host plants by tissues pushed into these vessels during the exploratory feeding of the potato leafhopper, Empeasca fabae, restricted the movement of sugars and starches in the leaves and in the meristematic tissue (DE LoNG,

Predicting the risk of weed infestation in winter oilseed rape crops

Abstract: Summary Chemical weed control before crop and weed emergence is a systematic practice in winter oilseed rape crops in France. It would be profitable both for farmers and the environment to predict the level of weed infestation early on in the growing season and to control weeds only when necessary using post-emergence weed control. The objective of this paper was to develop and evaluate simple models to predict weed biomass in oilseed rape crops. The model input variables were related to weed population characteristics and farmers’ practices. The models can be used to classify oilseed rape plots into two categories: plots with a level of weed infestation above a threshold or those with level of weed infestation below a threshold. A data set including 3 years of experiments, conducted across several regions in France, was used to estimate the parameters and to evaluate the models. High values of sensitivity and specificity were obtained when weed biomass was predicted as a function of sowing date, type of soil tillage, soil mineral nitrogen, crop density, weed density at emergence, and main characteristics of the most abundant weed species. Model performance strongly decreased when input variables related to the weed population were not taken into account. The best models correctly classified 90% of the plots with high weed infestation and 64% of the plots with low weed infestation.

Relationship of Incidence of Seedborne Xanthomonas campestris to Black Rot of Crucifers

Abstract: SCHAAD, N. W., W. R. SITTERLY, and H. HUMAYDAN. 1980. Relationship of incidence of seedborne Xanthomonas campestris to black rot of crucifers. Plant Disease 64:91-92. The relation of amounts of seedborne Xanthomonas campestris, determined by laboratory assays, to the incidence of black rot in the field was determined. Seeds infested naturally with X. campestris were mixed with healthy seeds, assayed for X. campestris, and seeded in a field in South Carolina. The pathogen was detected in laboratory assays in two of four samples with 0.01% infestation, whereas black rot developed in the field in three of four such samples. In 1976, field plots that initially contained 0.03, 0.07, and 0.14% infected plants resulted in high incidences of black rot. In 1977, the incidences of black rot were high in plots that initially contained 0.05% infected plants but not in plots that initially contained 0.01% infected plants. We conclude that laboratory assays can be used to detect levels of seed infestation that may or may not result in a high incidence of black rot in the field. Xanthomonas campestris is seedborne (3,5,7), and infested seed is an important source of inoculum (2,4,8,14,15). Several methods have been described for detecting the pathogen in or on seeds (1,9,11,13), but the number of infested seeds needed to initiate black rot in the field has not been determined. This information is essential to establish a minimum allowable percentage of seed infestation. This study was designed to determine the relationship of amounts of seed infestation to disease incidence in the field.