Use of Poultry Manure Combined with Soil Solarization as a Control Method for Meloidogyne incognita in Carnation.

The effectiveness of a combination of soil solarization and poultry manure (raw or pelletized) amendments for the control of root-knot nematode (Meloidogyne incognita) was tested in carnation (Dianthus caryophyllus) crops grown in in-ground beds under plastic-covered greenhouse conditions in southern Spain. Our trials demonstrated that soil solarization alone did not provide sufficient control of root-knot nematode, because the carnation growing season in this region only partly coincides with the most effective period for solarization, resulting in an insufficient duration of treatment during a key period for effectiveness. Chemical fumigation with 1,3-dichloropropene + chloropicrin prior to planting was effective in reducing nematode population densities in soil. Its effects spanned 9 months after planting, resulting in acceptable crop yields. In comparison, the combination of soil solarization and raw or pelletized poultry manure was slightly less effective than chemical fumigation for control of this pathogen but crop yields after 9 months were similar. However, the higher root gall indices observed after 9 months, in comparison with chemically fumigated plots, indicated the need for a reapplication of the organic manure treatment at the start of each successive growing season.

First Report of Phytophthora cactorum Causing Fruit Rot on Avocado in Spain.

The area of avocado (Persea americana Mill.) orchards in southern Spain has increased recently and is currently at 8,063 ha. Avocado production in this part of Spain was 72,581 t during 2003. During February 2004, apical necrosis was observed on avocado fruits (cv. Hass) in one orchard in Vélez-Málaga, Málaga Province, southern Spain. Dark brown lesions and necrotic flecking of the flesh also were observed on fruits. Isolations from the skin of the fruit previously washed with tap water and disinfested with 20% sodium hypochlorite on potato dextrose agar (PDA) consistently resulted in mycelial colonies. Sporangia produced on V8 juice by successive washing of mycelia with saline solution (1) measured 31 to 37.2 (33.3) × 21.7 to 28.8 (24.2) µm in size. The pathogen was identified as Phytophthora cactorum on the basis of morphological structures (mycelia, sporangia, chlamydospores, and oospores) formed when grown on V8 juice and PDA (2). To confirm pathogenicity, a mycelial suspension was obtained by blending mycelia grown for 1 week on PDA in 200 ml of sterile water. Three healthy avocado fruits were inoculated with the suspension by injection; three other fruits were inoculated by placing a drop of suspension on the unbroken skin of the fruit. The same number of fruit was inoculated as controls using sterile water instead of mycelial suspension. The inoculated fruits were incubated for 5 days in a moist chamber at 24°C in darkness. Spots appeared on all fruits for both inoculation methods, and the pathogen was isolated and identified as P. cactorum. No symptoms appeared on the control fruits. To our knowledge, this is the first report of P. cactorum causing fruit rot on avocado in Spain. References: (1) D. Chen and G. A. Zentmeyer. Mycologia 62:397, 1970. (2) G. M. Waterhouse and J. M. Waterston. No. 111 in: Descriptions of Pathogenic Fungi and Bacteria. CMI, Kew, Surrey, UK, 1966.

Soil Solarization in Established Avocado Trees for Control of Dematophora necatrix.

Four field experiments on the control of Dematophora necatrix in avocado orchards affected by white root rot were conducted in the Mediterranean coastal area of southern Spain during 1991 to 1994. In the unshaded locations of solarized plots, the maximal temperatures were 35 to 42°C, depending upon the year and soil depth (15 to 60 cm). Temperature increases attributable to soil solarization ranged between 4 and 8°C in unshaded areas, whereas for shaded areas they were approximately 4°C. Inoculum recovery was decreased in root samples buried at 15 to 30 cm in unshaded locations of both solarized and unsolarized plots after 3 to 5 weeks, whereas 4 to 8 weeks of solarization were required for the elimination of the pathogen buried at depths of 45 to 60 cm. In contrast, inoculum recovery ranged from 30 to 60% for samples in shaded locations of unsolarized plots. D. necatrix was not recovered from roots of infected trees in solarized plots sampled 9 months after solarization, whereas recovery from roots in unsolarized plots was similar to levels before solarization. Soil solarization in established orchards was successful in reducing viability of inoculum buried in soil and eliminated inoculum in infected roots of live trees.