Stem Radial Growth Is Negatively Related to Tree Defoliation and Damage in Conifers, Northern Italy

Although several manipulative experiments provided evidence for a negative effect of defoliation on tree growth, results from observational studies were less univocal. This may be due to the ability of observed defoliation to reflect the health status of individual trees, to the influence of site condition and to the amplitude of time window used for growth assessment. Here, we investigated the relationship between two tree health indicators (crown defoliation, damage symptoms) and annual (measured by tree-ring width on 69 Norway spruce trees) and periodical (5-year and 10-year diameter increments, 346 trees from five coniferous species) tree growth. Data originated from 14 (seven for tree rings) ICP Forests Level I plots in Trentino, northern Italy. Diameter, defoliation and damage were measured between 1997 and 2011 as part of the annual crown condition survey, while cores for tree-rings were collected on a sub-sample of trees in 2012. We carried out regression modeling combined with model selection in one-step (periodical data) and two-step (annual data) approaches, using moving averages for the annual data with varying time window widths. Our results indicated an overall negative correlation between defoliation and annual or periodical stem diameter growth. The relationship between defoliation and growth changes in relation to the time window considered, and becomes stronger when data are aggregated over longer time windows (>3 years), when also the occurrence of damage symptoms plays a significant role. The effect of the amplitude of the time windows for data aggregation is probably due to the mechanisms behind the defoliation-growth relationship, which may change according to the causal factors involved. In particular, when larger time windows are considered, short-term fluctuations are likely to be smoothed out, and more general patterns may emerge. We concluded that radial growth is significantly negatively related to defoliation, and this supports the use of defoliation as a rapid indicator for forest health and vitality.

Salinity Effect on Plant Physiological and Nutritional Parameters of New Huanglongbing Disease-Tolerant Citrus Rootstocks

Salinity is a major agriculture problem for citrus in the Mediterranean basin, which is a major global producer region. Citrus crops are also threatened by emerging diseases such as Huanglongbing (HLB). The use of different rootstocks increases the variability of citrus plant material in orchards, thus preventing extensive damage caused by abiotic and/or biotic diseases. In this work, we have evaluated the salinity response of five citrus rootstocks (US942, US897, X639, Forner Alcaide No. 5 and Carrizo citrange) some of which have known tolerance to HLB, under Mediterranean conditions. Four treatments with different salt concentrations (0, 25, 50 and 75 mM of NaCl) were applied by watering the plants three times per week for eleven weeks. Chlorophyll index (SPAD), growth and plant symptom parameters were recorded on a biweekly basis. At the end of the trial, roots, stem and leaves biomass and plant mineral content were obtained. The increasing concentration of NaCl resulted in visible leave damage symptoms for all citrus rootstocks assayed, hindering plant growth in all citrus rootstocks assayed, except for X639. The highest concentration of toxic ions in leaves was detected in Carrizo citrange and US897 for Cl−, while the lowest concentration of Na+ was obtained in X639. These results provide growers with information about the sensitivity to salinity of different citrus rootstocks.

Galling Damage to Woody Ornamentals: Diagnosis and Potential Causes

Galling or witch’s broom damage on the newly expanding buds and leaves of woody ornamental plants has become increasingly common. Diagnosing this damage can be difficult because the most common causes are obscure or occur well before damage symptoms appear. This -page fact sheet written by and published by the UF/IFAS is intended to help landscape managers, nursery growers, and pest control professionals diagnose characteristic galling damage, mitigate damage that occurs, and, when possible, prevent it from occurring.

Pratylenchus in sugarcane: a diminishing problem?

This chapter focuses on the economic importance, host range, geographical distribution, damage symptoms and biology and life cycle of Pratylenchus brachyurus, P. neglectus, P. scribneri and P. zeae infesting sugarcane in South Africa. Information on their interactions with other nematodes and pathogens, the efficacy and optimization of some recommended integrated nematode management programmes and future nematode research requirements are also presented.

The soybean cyst nematode: pervasive and destructive to soybean production in the mid-western United States.

This chapter focuses on the economic importance, host range, geographical distribution, damage symptoms and biology and life cycle of the soyabean cyst nematode, Heterodera glycines, a pervasive and destructive pest to soyabean production in the mid-western USA. Some information on its interaction with other plant pathogens, the efficacy and optimization of some recommended integrated nematode management practices and future outlook and research requirements are also presented.

The beet cyst nematode (Heterodera schachtii): an ancient threat to sugar beet crops in Central Europe has become an invisible actor.

The beet cyst nematode (BCN) was one of the first discovered plant parasitic nematodes. Heterodera schachtii was observed in 1859 in Halle in Central Germany by the botanist Herman Schacht and described later by Adolf Schmidt in 1871, who named this cyst nematode species after its original discoverer. Partly due to the lack of knowledge about the effect of sugar beet monocultures on the population build-up of BCN, this nematode had a devastating impact on sugar production in 1876 that led to the shutdown of 24 sugar factories in Germany. This chapter discusses the economic importance, distribution, host range, damage symptoms, biology and life cycle, interactions with other nematodes and pathogens, recommended integrated management, and management optimization of H. schachtii. Future research requirements and future developments are also mentioned.

Improving the management of plant parasitic nematodes in banana: integration of technologies and responding to the demand of the consumers and markets.

This chapter discusses the economic importance, geographical distribution, host range, damage symptoms, biology and life cycle, interactions with other nematodes and pathogens, recommended integrated management, and management optimization of Radopholus similis infesting bananas. Future research requirements and future developments are also mentioned.

Mitigating a galling problem in California's carrot production.

This chapter discusses the economic importance, geographical distribution, host range, damage symptoms, biology and life cycle, interactions with other nematodes and pathogens, recommended integrated management, and management optimization of Meloidogyne incognita infesting carrots in California, USA. Future research requirements and future developments are also mentioned.

Integrated management of Meloidogyne incognita, the most economically damaging pathogen of cotton in the south-eastern United States.

This paper focuses on the economic importance, host range, geographical distribution, damage symptoms and biology and life cycle of Meloidogyne incognita, the most economically damaging pathogen of cotton in the south-eastern USA. Some information on their interactions with other nematodes and pathogens, efficacy and optimization of some recommended integrated nematode management systems and future outlook and research requirements on nematode management are also presented.