Search Results

You are looking at 1 - 10 of 2,199 items for :

Clear All
Open access

Michael Fidanza, Derek Settle and Henry Wetzel

Fairy ring is considered one of the most common turfgrass diseases globally, and over 60 species of basidiomycetes are known to cause fairy ring symptoms in turf, making it one of the most common turfgrass diseases globally ( Couch, 1995 ; Smiley

Full access

Terri W. Starman, Shannon E. Beach and Kristen L. Eixmann

determine qualitative and quantitative shelf life longevity of 21 cultivars of cool- and warm-season vegetative annuals to determine the effect of shipping duration and to characterize postharvest decline symptoms. This study was designed to lead to further

Restricted access

Germán V. Sandoya, Krishna Subbarao and Ryan Hayes

secondary roots of lettuce and moves into the taproot through the vascular system ( Vallad and Subbarao, 2008 ). In susceptible plants, the fungus moves into the foliage of the plant causing wilting, chlorosis, and necrosis, and finally death. These symptoms

Full access

Timothy K. Broschat

Ixoras (Ixora L.) growing in calcareous sandy soils are highly susceptible to a reddish leaf spot disorder. Symptoms appear on the oldest leaves of a shoot and consist of irregular diffuse brownish-red blotches on slightly chlorotic leaves. Symptoms of K deficiency, P deficiency, and both K and P deficiency were induced in container-grown Ixora `Nora Grant' by withholding the appropriate element from the fertilization regime. Potassium-deficient ixoras showed sharply delimited necrotic spotting on the oldest leaves, were stunted in overall size, and retained fewer leaves per shoot than control plants. Phosphorus-deficient plants showed no spotting, but had uniformly brownish-red older leaves and olive-green younger foliage. Plants deficient in both elements displayed symptoms similar to those observed on landscape plants. Symptomatic experimental and landscape ixoras all had low foliar concentrations of both K and P.

Free access

Bruce W. Wood and Charles C. Reilly

Bearing pecan [Carya illinoinensis (Wangenh.) K. Koch] trees overly stressed by crop load and premature autumn defoliation either died or were severely damaged by -3°C in mid-November. Orchard damage was associated with death of tree roots during the dormant season. Exposure of stressed trees to -5°C in mid-March produced an atypical, but distinct, bottom-to-top-of-canopy gradient in bud death and reduced growth of shoots and foliage that was consistent with the pattern of reduced carbohydrate reserves of associated support shoots. Additionally, the foliage of damaged trees contained higher concentrations of N, P, K, Ca, Mg, Mn, Fe, and B. Trees did not exhibit traditional symptoms of cold damage, thus these findings extend cold injury diagnostic criteria to include both root and tree death during the dormant season and also a distinct gradient in shoot death during early spring. Damage by cold appears to be preventable by avoiding excessive tree stress due to overcropping and premature defoliation.

Free access

Giuseppe Cimò, Riccardo Lo Bianco, Pedro Gonzalez, Wije Bandaranayake, Edgardo Etxeberria and James P. Syvertsen

overaccumulation of carbohydrates in leaves ( Bove, 2006 ; Garnier and Bove, 1983 ). The earliest visible symptoms of HLB in leaves are vein yellowing and asymmetrical chlorosis referred to as “blotchy mottle,” thought to be the result of starch accumulation

Free access

Uri Yermiyahu, Alon Ben-Gal and Pinchas Sarig

Table grape production has recently become popular in arid and semiarid regions where conditions of salinity and excess boron (B) can be prevalent. This study addresses B toxicity in grapevine to define toxicity symptoms and evaluate growth, production, and B accumulation. The effect of excess B on grapevines (Vitis vinifera L. cv. Sugraone) was evaluated in a 4-year study in Israel's Jordan Valley. Vines were grown in 60-L perlite-filled containers and irrigated with complete nutrient solutions with four B concentrations: 0.03, 0.12, 0.21, and 0.31 mm. Vines were monitored for growth, yield, and B accumulation. Boron accumulation in leaves correlated with B toxicity symptoms that materialized as chlorosis and necrosis of leaves beginning at their margins, reduced leaf size, and reduced internodal distance between adjacent leaves. Boron accumulated in grapevine leaves linearly as a function of increased B in irrigation solution with time and with age of leaves. The highest B levels were found at the end of each season and in the oldest leaves. No long-term (multiyear) effect of exposure to B was observed because similar accumulation patterns and levels were found in each year of the experiment. Hence, consistently sampled diagnostic leaves and time of sampling for B analysis is seen to be critical to provide valid comparisons between vines or over time. Boron supply influenced vine growth. At low levels of B (0.03 mm), canopy development was restricted but trunk size was not. At high levels of B (0.21 and 0.31 mm), substantial visual symptoms of B toxicity were observed, and the rate of trunk growth was reduced, but pruning biomass was not influenced. Despite severe visual toxicity damage and reduced overall growth rates, commercial fruit yield of the vines remained unaffected by high environmental B levels.

Free access

Hong Chen, Greg McCollum, Elizabeth Baldwin and Jinhe Bai

southern China in 1919 ( Bové, 2006 ). After being infected with C Las, citrus trees develop HLB symptoms including decline with typical symptoms such as reduced plant height, yellow shoots, blotchy mottled leaves, canopy thinning, premature abscission of

Free access

Bruce W. Wood

Nickel is an often-overlooked plant ( Brown et al., 1987 , 1990 ) and animal ( Welch and Graham, 2005 ) essential micronutrient. Although Ni deficiency in plants severe enough to trigger visual symptoms is relatively rare, compared with other

Free access

Bijan Dehgan, Joseph E. Durando and Thomas H. Yeager

Cycas revoluta, an important ornamental palm-like plant of warmer regions of the world, often exhibits a foliar chlorotic/necrotic dieback in landscapes. Despite a weak correlation (r2 ≤ 0.28) of percent symptoms with soil nutrient levels or pH, symptom severity was correlated more notably (r2=0.49) with Mn and had even a higher correlation (r2 = 0.61) with the Fe : Mn ratio. Anatomical examination of chlorotic leaflets indicated an accumulation of tanniniferous cells but did not provide direct evidence of Mn deficiency. Although field surveys indicated a link between low Mn levels and Fe : Mn ratio in the plant and appearance of the disorder, the manifestation of symptoms could not be directly correlated with any edaphic factors. However, identical symptoms were induced in young plants by withholding Mn in a solution culture experiment. Application of chelated Mn on expanding leaves alleviated the disorder, but only for the current growth flush. Irrigation frequency in concert with other cultural practices probably are more responsible for development of symptoms than actual soil Mn inadequacy. In consideration of acute susceptibility of cycads to micronutrient deficiencies, plants should be supplied with a complete micronutrient fertilizer during growth in containers and before field planting.