Sunflower (Helianthus annuus L.) has emerged as an economically important crop in Pakistan due to its significant share in vegetable oil production. The plant metabolic processes require protein to increase the vegetative, reproductive growth and yield of the crop. The protein is wholly dependent upon the amount of nitrogen fertilization available for plant use. ) and grain yield (3809 kg·ha -1 ) compared to the other N rates. The maximum oil content (46.2%) was observed in Hysun-38 without application of N fertilizer (N 1 ), while the minimum oil content (40.6%) was observed from N 5 treatment. In conclusion, the application of 180 kg·ha -1 N to Hysun-38 provided the best combination for good yield in sunflower crop under the prevailing sub-humid conditions of Pakistan.

The incidence of postharvest fruit rot and associated fungi was studied in stored cranberries in Michigan in 2000 and 2001. Ripe cranberries were harvested from eight commercial farms in southwest and northeast Michigan, including the Upper Peninsula. Eight cranberry cultivars were represented: Stevens, Searles, Le Munyon, Pilgrim, Ben Lear, Bergman, Beckwith, and WSU 61. Fruit rot incidence was assessed within 1 week after harvest. Remaining sound fruit was stored for 2 months at 5°C, and fungi were isolated from rotted fruit after 1 and 2 months of storage. Year and region, but not cultivar, significantly affected the overall rate of rot development in storage. Storage rot levels generally were lower in 2001 than in 2000, particularly in southern Michigan. A high incidence of field rot at harvest did not necessarily lead to a high incidence of storage rot. Storage rot tended to be more severe in the northern than in the southern growing region. Fungi most frequently associated with storage rot were Fusicoccum putrefaciens, Colletotrichum acutatum, Coleophoma empetri, Phomopsis vaccinii, and Phyllosticta elongata. F. putrefaciens was the predominant storage rot fungus in northern Michigan in both years and caused up to 80% fruit rot in storage. C. empetri and P. elongata also were isolated more frequently from beds in northern than southern Michigan in 2001. The cvs. Pilgrim and Stevens were more susceptible to storage rot caused by Colletotrichum acutatum, and Bergman and WSU 61 were more susceptible to storage rot caused by Phomopsis vaccinii than some of the other cultivars.

Tomato spotted wilt virus (TSWV), a member of the genus Tospovirus (family Bunyaviridae), is an important plant virus that causes severe damage to peanut (Arachis hypogaea) in the southeastern United States. Disease severity has been extremely variable in individual fields in Georgia, due to several factors including variability in weather patterns. A TSWV risk index has been developed by the University of Georgia to aid peanut growers with the assessment and avoidance of high risk situations. This study was conducted to examine the relationship between weather parameters and spotted wilt severity in peanut, and to develop a predictive model that integrates localized weather information into the risk index. On-farm survey data collected during 1999, 2002, 2004, and 2005 growing seasons, and derived weather variables during the same years were analyzed using nonlinear and multiple regression analyses. Meteorological data were obtained from the Georgia Automated Environmental Monitoring Network. The best model explained 61% of the variation in spotted wilt severity (square root transformed) as a function of the interactions between the TSWV risk index, the average daily temperature in April (TavA), the average daily minimum temperature between March and April (TminMA), the accumulated rainfall in March (RainfallM), the accumulated rainfall in April (RainfallA), the number of rain days in April (RainDayA), evapotranspiration in April (EVTA), and the number of days from 1 January to the planting date (JulianDay). Integrating this weather-based model with the TSWV risk index may help peanut growers more effectively manage tomato spotted wilt disease.

Samples of ripe fruit were taken at harvest from all eight commercial cranberry farms in Michigan over a 3-year period to determine the distribution and incidence of fruit rot diseases and the fungal pathogens associated with rotted fruit. Totals of 23, 33, and 28 beds were sampled in 1999, 2000, and 2001, respectively. Fruit rot incidence varied widely among beds and farms and ranged from 5 to 97% (mean 33.4%) in 1999, 1 to 91% (mean 26.3%) in 2000, and 1 to 67% (mean 12.8%) in 2001. Differences in fruit rot incidence were observed among cultivars, but rankings differed among farms. In general, cultivars Ben Lear, Bergman, and Pilgrim tended to have lower and Beckwith and WSU61 higher fruit rot incidence than other cultivars grown in the same location. Colletotrichum acutatum, Pestalotia vaccinii, and Phyllosticta vaccinii were the fungi most frequently recovered from rotted fruit. Fusicoccum putrefaciens, Phomopsis vaccinii, Physalospora vaccinii, Allantophomopsis lycopodina, Coleophoma empetri, and Botrytis cinerea were isolated occasionally in 1999. The isolation frequency of Physalospora vaccinii, Phomopsis vaccinii, and C. empetri increased markedly in 2000. Glomerella cingulata was first detected in 2001. Fusicoccum putrefaciens was most common in the northern and Glomerella cingulata in the southern growing areas. A comparison of sound and rotted fruit from selected beds showed that Phyllosticta elongata predominated in sound fruit, whereas G. cingulata predominated in rotted fruit.

In recent years, outbreaks of nonnative invasive insects and pathogens have caused significant levels of tree mortality and disturbance in various forest ecosystems throughout the United States. Laurel wilt, caused by the pathogen Raffaelea lauricola (T.C. Harr., Fraedrich and Aghayeva) and the primary vector, the redbay ambrosia beetle (Xyleborus glabratus Eichhoff), is a nonnative pest-disease complex first reported in the southeastern United States in 2002. Since then, it has spread across eleven southeastern states to date, killing hundreds of millions of trees in the plant family Lauraceae. Here, we examine the impacts of laurel wilt on selected vulnerable Lauraceae in the United States and discuss management methods for limiting geographic expansion and reducing impact. Although about 13 species belonging to the Lauraceae are indigenous to the United States, the highly susceptible members of the family to laurel wilt are the large tree species including redbay (Persea borbonia (L.) Spreng) and sassafras (Sassafras albidum (Nutt.) Nees), with a significant economic impact on the commercial production of avocado (Persea americana Mill.), an important species native to Central America grown in the United States. Preventing new introductions and mitigating the impact of previously introduced nonnative species are critically important to decelerate losses of forest habitat, genetic diversity, and overall ecosystem value.

This study examined the role of the fungi Dactylella oviparasitica and Fusarium oxysporum in the beet-cyst nematode (Heterodera schachtii) suppressiveness exhibited by a southern Californian soil. In prior research, the abundance of D. oviparasitica rRNA genes positively correlated with high levels of suppressiveness, whereas the abundance of F. oxysporum rRNA genes positively correlated with minimal to moderate levels of suppressiveness. In this report, both fungi were added to fumigation-induced nonsuppressive soil, planted with Swiss chard, and infested with H. schachtii juveniles. After two nematode generations, D. oviparasitica strain 50 reduced the population densities of H. schachtii eggs and juveniles to those in the suppressive soil and H. schachtii cysts to levels lower than in the suppressive soil. F. oxysporum did not significantly reduce H. schachtii populations. These results suggest that D. oviparasitica strain 50 plays a major role in the suppression of H. schachtii population development in this southern Californian soil.

Early leaf spot of peanut (Arachis hypogaea L.), a disease caused by Cercospora arachidicola S. Hori, is responsible for an annual crop loss of several million dollars in the southeastern United States alone. The development of early leaf spot on peanut and subsequent spread of the spores of C. arachidicola relies on favorable weather conditions. Accurate spatio-temporal weather information is crucial for monitoring the progression of favorable conditions and determining the potential threat of the disease. Therefore, the development of a prediction model for mitigating the risk of early leaf spot in peanut production is important. The specific objective of this study was to demonstrate the application of the high-resolution Weather Research and Forecasting (WRF) model for management of early leaf spot in peanut. We coupled high-resolution weather output of the WRF, i.e. relative humidity and temperature, with the Oklahoma peanut leaf spot advisory model in predicting favorable conditions for early leaf spot infection over Georgia in 2007. Results showed a more favorable infection condition in the southeastern coastline of Georgia where the infection threshold were met sooner compared to the southwestern and central part of Georgia where the disease risk was lower. A newly introduced infection threat index indicates that the leaf spot threat threshold was met sooner at Alma, GA, compared to Tifton and Cordele, GA. The short-term prediction of weather parameters and their use in the management of peanut diseases is a viable and promising technique, which could help growers make accurate management decisions, and lower disease impact through optimum timing of fungicide applications.

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