Plant Health Laboratories

Chemistry and Entomology Laboratories

Chemistry Laboratory (Soil and Irrigation water)

The Chemistry Laboratory (soil and irrigation water) has recently been established from what was previously known as the Agricultural Services Laboratory (ASL). The Laboratory is situated at the Agricultural Research and Development Centre in Għammieri (Marsa) and now forms part of the Plant Health Department.

The aims of the Chemistry Laboratory (soil and irrigation water) include:

§ The provision of Laboratory services for soil and irrigation water testing;

§ The performance of diagnostic analysis in conjunction with research programs in soil and irrigation water; and

§ The assistance to the farming community and the general public in soil and water use.

Activities and Facilities

Activities

The Chemistry Laboratory (soil and irrigation water) is mainly responsible for the testing of soil and water samples brought to its premises by the general public, mainly by farmers. Also, it has participated in various projects for which soil analysis had been required. For instance the soil samples collected and sampled as part of the Maltese Soil Information System (MALSIS) project.

The main activities carried by the Chemistry Laboratory can be summarized as follows:

- Testing of soil and water for salinity problems;

- Testing of soil for major plant nutrients;

- Soil physics examination for the determination of soil hydraulic properties and particle size distribution and

- Examination by atomic absorption spectrophotometry for the determination of minerals and pollutants in soil and water.

Facilities

The Chemistry Laboratory is well equipped with apparatus for physico-chemical analysis. These include equipment for the chemical analysis such as pH and conductivity meters, atomic absorption spectrophotometer, flame photometer, and ion selective electrode meter. As for the physical analysis the equipment include the Scheibler apparatus and the Eijkelkamp pipette apparatus.

Laboratory Services

As indicated earlier, this Laboratory conducts services on both soil and water. Those carried on soil are soil salinity (pH, electrical conductivity, soluble sodium and chloride), soil fertility (potassium, nitrate-nitrogen), soil physical properties (particle size distribution, organic matter content) and soil pollutants/heavy metals (lead, chromium, nickel, zinc, copper and iron). As regards water the services are carried on water used for irrigation on which test are conducted to determine the pH, the electrical conductivity, calcium + magnesium, soluble sodium and sodium adsorption ratio.

Entomology Lab

This lab is also situated at the Agricultural Research and Development Centre in Għammieri, Marsa. It caters for all aspects related to the study of insects. Some work in also carried out on mites of agricultural importance. This lab which is an integral part of the Diagnostic and Control Unit, deals with identification of diverse groups of insects from most orders. Use of specialized keys is undertaken to arrive to species identification. In case of a number of insect groups such as beetles, flies and other hard body insects identification is carried out directly on the dried insect specimens. However, in case of soft body insects such as thrips, whiteflies, aphids, jumping plant-lice and scale insects (all of which have important species of plant quarantine significance), permanent slide mounts are done so as to study the detailed morphology of these insects using compound microscopy. The method used is adopted from Ben-Dov & Hodgson (1997).

Mycology Lab

The Mycology Lab aims to “Intercept and detect plant diseases caused by fungal pathogens”. The overall responsibilities of the Mycology Lab are:

- Diagnoses of diseased plant materials in all respects to Koch’s Postulates submitted to the Plant Health Department.

- Uphold all of obligations of the Plant Health Department related to fungal diseases locally to the Central Government of Malta and internationally to the European Union (EU) as stipulated by Legal Notices L.N. 96 and L.N.271 of 2004 Plant Quarantine Act, 2001 (ACT NO. XVIII OF 2001), Council Directive 2000/ 29/EC and Commission Decisions 2002/757/EC and 2004/426/EC.

Nematology Lab

The Nematology Laboratory is situated at the Agricultural Research and Development Centre in Għammieri, Marsa and forms part of the Diagnostic and Control Unit. At this laboratory, nematodes, small organisms usually less than 5 mm in length are analysed. This group of organisms is highly diverse with species occupying all sorts of niches. With respect to agriculture, plant parasitic nematodes can be particularly harmful and could cause severe crop losses. Apart from the fact that these plant parasitic nematodes can do direct damage to the plant, some species are also able to transmit viral diseases. A notable example is Xiphinema index which is often found associated with roots of grapevines and Ficus carica. This nematode is a vector of the Fan Leaf Virus in grapevines.

Suspected presence of plant parasitic nematodes are handled as follows. Soil samples near roots of affected plants/trees are taken to the labs for further investigation. These samples (usually consisting of 1 kg soil) are immediately dissolved in water, agitated and after 5 minutes, the liquid part is decanted over a 75 micrometer sieve. What is collected in the sieve is then washed and placed in a smaller 75 micrometer sieve immersed in water for 24-48 hours. After this the water is diagnosed for the presence of plant parasitic nematodes using a dissecting microscope. Nematodes are then stored in 5% formaline solution for further study under microscopy. Another extraction method is through the use of centrifuge, but this method is rarely used here.

Generally only semi-permanent slides are done to examine nematodes for species identification using the compound microscope. Most often species identification is difficult and samples are send abroad for further examination.

Bacteriology Lab

The Bacteriology Section aims to test for and monitor quarantine plant bacteria to prevent the introduction and spread of quarantine diseases in the Maltese Islands. Quarantine plant bacteria tested as yet include:

- The Potato Ring Rot (Clavibacter michiganensis var sepedonicus), as required by Council Directive 93/85/EEC on the Control of Potato Ring Rot and

- The Potato Brown Rot (Ralstonia solanacearum) Council Directive 98/57/EC on the Control of Ralstonia solanacearum (Smith) Yabuuchi et al.

These pathogens pose a serious threat to potato cultivation, which is one of the most economically important crops in the Maltese Islands. As such, annual surveys are carried out involving field visits to potato crops in different areas in the Maltese Islands. Visual inspections for Bacterial Wilt symptoms are made and random samples are taken for laboratory testing. Screening tests include Gram Staining, Immunoflorescence assays and culturing of bacteria on semi-selective media. Additional and confirmatory tests include Polymerase chain reaction inoculation of indicator plants. All tests are performed according to the relevant EU Directive.

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