Relationships between agronomic factors and epidemics of Phytophthora branch canker of citrus in southwestern Spain

Abstract

Phytophthora branch canker, caused by Phytophthora citrophthora, has been an increasing problem in clementine (Citrus reticulata) production in Spain during last years. The disease was particularly severe in the new citrus-growing areas of the southwestern coastal areas in Huelva Province. Recent studies revealed that disease emergence was not related to either genetic drift or host specificity changes in P. citrophthora population. Therefore, the possible association of agronomic factors with the disease was investigated. A total of 110 orchards were selected arbitrarily from the main citrus-growing areas in Huelva Province. The presence of branch cankers together with agronomic factors including soils, cultivars, rootstocks, irrigation, pruning, techniques to improve fruit production, fungicide treatments, presence of brown rot of fruit and frost damage were recorded. Logistic regression analysis was used to detect correlations between the agronomic factors studied and disease prevalence. Phytophthora branch canker was significantly associated with mature clementine orchards. Sweet orange and hybrid cultivars as well as young clementine orchards were less affected by the disease. Although disease was less frequent in Salorthid soils, alternative high resolution procedures are required to draw conclusions about the effect of soil properties on disease prevalence. As in other Phytophthora-induced diseases, soil flooding during the rainy season was correlated positively with the prevalence of branch cankers. Improving fruit production by branch scoring showed a strong positive correlation with Phytophthora branch canker. This is the first time that girdling has been associated with Phytophthora disease Eur J Plant Pathol (2012) 133:577-584

Response of microbial organisms (aquatic and terrestrial) to pesticides

“…Captan was the most studied (111 case studies), followed by chlorotalonil (100), metalaxyl (80) and mefenoxam (59). Among the aquatic database, the most studied were chlorotalonil (102) followed by triclosan and epoxiconazole (both 14), captan (12) and tebuconazole (8).…”

“…Among insecticides (Table 24), the total number of records was 850 for the terrestrial lot (covering 60 compounds in total) and 81 (coming from 13 compounds) for the aquatic. Most represented were chlorpyrifos (124 case studies), fenamiphos (91) and teflubenzuron (50) for the terrestrial lot ( Figure 7); dimethoate (20), pirimicarb (12), aldrin (8), lindane (8) and endosulfan (8) for the aquatic ( Figure 8). Finally, a few chemicals belonging to other minor classes such as acaricides, nematicides, bactericides and plant growth regulators were also included (Table 25): the total number of records related to these other classes was 136 for the terrestrial database and only 3 for the aquatic (all 3 referred to Azocyclotin, an acaricide).…”

Citrus Pruning in the Mediterranean Climate: A Review

“…Pruning can also stimulate the effects of nematode infection [58]. Although some works indicate that the pruning of symptomatic branches can control citrus variegated chlorosis [59], some authors consider it impossible to control wood diseases such as virus, bacteria, or fungi diseases through pruning [68][69][70][71][72][73][74][75].…”

Impact of kiwifruit bacterial canker on productivity of cv. Hayward kiwifruit using observational data and multivariable analysis

“…An observational study using multivariable explanatory models was identified as an approach that could quantify productivity impacts in commercial orchards subjected to different management regimes and other factors affecting disease risk. There has been increased interest in applying multivariable models to experimental data (Garrett et al ., ; Scherm et al ., ), but the use of observational studies instead of experimental studies is rare in plant protection research, with only a small number of examples (Dallot et al ., ; Thebaud et al ., ; Vicent et al ., ). However, these methods are widely used in studies of animal health and production (Dohoo et al ., ; Alarcon et al ., ).…”