Residues of Deltamethrin in Pine Needles and Pine Nuts of Catalonia (Spain).

In recent years, recurrent droughts have weakened stone pine (Pinus pinea) forests and facilitated the emergence of harmful pests and diseases, including the Leptoglossus occidentalis. The production of stone pine nuts has declined over the past five years. To control this hemipteran pest, a synthetic pyrethroid insecticide called deltamethrin is being tested. However, it is necessary to estimate the residue left by these treatments in forest stands. Therefore, a fast and robust analytical procedure was developed based on QuEChERS clean-up extraction, followed by gas chromatography coupled with an electron capture detector. This optimized method can detect residual concentrations of deltamethrin in pine nuts and pine needles up to 0.1 and 6 µg kg-1, respectively, with a limit of quantification of 0.4 and 20 µg kg-1. Great recoveries (between 84 and 102%) were obtained for both matrices, and no matrix effect was observed. The results showed that two weeks after spraying, the deltamethrin content in the needles of stone pines decreased by up to 75%, and after nine months, its presence was like that of nontreated trees.

Advances in Rootstock Breeding of Nut Trees: Objectives and Strategies.

The production and consumption of nuts are increasing in the world due to strong economic returns and the nutritional value of their products. With the increasing role and importance given to nuts (i.e., walnuts, hazelnut, pistachio, pecan, almond) in a balanced and healthy diet and their benefits to human health, breeding of the nuts species has also been stepped up. Most recent fruit breeding programs have focused on scion genetic improvement. However, the use of locally adapted grafted rootstocks also enhanced the productivity and quality of tree fruit crops. Grafting is an ancient horticultural practice used in nut crops to manipulate scion phenotype and productivity and overcome biotic and abiotic stresses. There are complex rootstock breeding objectives and physiological and molecular aspects of rootstock-scion interactions in nut crops. In this review, we provide an overview of these, considering the mechanisms involved in nutrient and water uptake, regulation of phytohormones, and rootstock influences on the scion molecular processes, including long-distance gene silencing and trans-grafting. Understanding the mechanisms resulting from rootstock × scion × environmental interactions will contribute to developing new rootstocks with resilience in the face of climate change, but also of the multitude of diseases and pests.

Apical Necrosis and Premature Drop of Persian (English) Walnut Fruit Caused by Xanthomonas arboricola pv. juglandis.

Etiological and epidemiological aspects of apical necrosis of walnut fruit were studied on cultivars Chandler, Franquette, and Hartley in a Spanish walnut orchard during 2007 and 2008. Affected fruit showed brown necrosis beginning at the blossom end of nuts; these symptoms differed from lesions of common blight of walnut (Xanthomonas arboricola pv. juglandis). X. arboricola pv. juglandis was consistently isolated from apical lesions throughout the growing season. Field isolates reproduced symptoms observed in the orchard when inoculated on immature detached walnut fruit in the laboratory. Sporadic occurrence of Fusarium spp. and Alternaria spp., mainly in dropped fruit, was attributed to secondary colonization of apical lesions that were originally caused by X. arboricola pv. juglandis. Apical necrosis and common blight were similar in disease epidemiology and cultivar susceptibility; a major increase in epidemics occurred at initial fruit development, and cvs. Chandler and Hartley were more affected than cv. Franquette. Our results suggest that apical necrosis is a new manifestation of walnut blight characterized by distinct symptoms and severe premature fruit drop.

Evaluation of a Reduced Copper Spraying Program to Control Bacterial Blight of Walnut.

Walnut blight, caused by Xanthomonas arboricola pv. juglandis, is currently controlled in western Europe through a standard schedule of seven applications of sprayed copper from bud break until harvest. A reduced spray schedule, with the last four applications omitted, was compared to the standard program in experimental plots for 3 years. Bacterial population levels in the spring were not significantly different between trees subjected to reduced sprays and those subjected to the standard schedule, but in summer they were higher in the trees that received fewer sprays compared with the standard program. However, disease control on nuts was similar or even better with the reduced spraying program than with the standard program, with the additional economic benefit of four fewer copper applications. After 3 years of using the reduced spray program, the amount of copper accumulated in the soil was significantly lower (about half) than that found in the soil where the standard spray program was implemented.