QUALITY CONTROL AND QUALITY OF COMMERCIAL PRODUCTS

Consumer acceptance of nematode products is determined by their ease of use, efficacy, and price. The development of mass-production technology has led to the availability of nematode products at prices comparable to the standard insecticides in many markets. The ease of use of nematode products is constantly being improved through formulation research. The easy-to-use WDG formulation has expanded the market potential of nematode products significantly. Efficacy is perhaps the most important factor determining quality of nematode products, and depends on many factors, but preservation of high nematode viability and virulence during large-scale production and formulations are essential components of a quality control strategy. The most important production factors affecting nematode quality are the type of medium, amount and type of antifoam, bacterial phase, delivery of oxygen, sheer stress, production and storage temperature, and contamination. The quality of the nematodes that survive the rigors of the manufacturing process is analyzed by determining their shelf life and virulence. Nematode shelf life is predicted from storage energy reserves (e.g., dry weight or total lipid content) of 11 nematodes; virulence potential is measured using insect bioassays. Nematode virulence is the most important component of nematode quality. Virulence/pathogenicity can be measured by different methods, including I : I bioassay , LC50s , invasion or establishment efficiency , invasion rate , and number of bacteria . One-on-one bioassay is perhaps the most versatile method of virulence assessment. Most of the infectivity assays using multiple nematodes and single or multiple hosts are considered inappropriate for quality control purposes because of the host-parasite interaction effects, such as recruitment and over dispersion of natural parasite populations. The one-on-one filter-paper assay and its modifications compare virulence of any nematode species with a predetermined standard against a very susceptible host. This method measures the proportion of infective nematodes in a population, is sensitive to impaired nematodes, and is appropriate for nematode species that have a lethal level of one IJ/larva. New bioassay methods are required for nematode species that do not kill G. mellonella larvae at I: 1 ratio, so that the principal thesis of this method could be applied.

Abstracts
CHINA-FATTY ACID
1. Jian-Heng; Yang-Huaiwen; Zhang-Gangying; Zhang-Shangao; 1997. Comparative study on fatty acids of Steinernema carpocapsae cultured by different media. Chinese-agricultural-sciences:-for-the-compliments-to-the-40th-anniversary-of-the-founding-of-the-Chinese-Academy-of-Agricultural-Sciences. 115-121; 17 ref.
AB: Of 4 kinds of media tested, the lowest total relative amount of nematode fatty acids was obtained in S. carpocapsae cultured on the medium consisting mainly of plant proteins, and the highest was obtained from the in vivo culture. Media containing plant proteins (treatments 1 and 3), had more linoleic and linolenic acids and less palmitic acid, while the media containing animal proteins such as insect tissues (treatments 2 and 4) had more palmitic and oleic acids.

CANADA- TEMP & LIPIDS
2. Jagdale-GB; Gordon-R. 1997. Effect of temperature on the composition of fatty acids in total lipids and phospholipids of entomopathogenic nematodes. Journal-of-Thermal-Biology. 22:4-5, 245-251; 23 ref.
AB: Gas liquid chromatography was used to determine the composition of fatty acids in total lipids and phospholipids of Steinernema feltiae Umea strain, S. carpocapsae All strain, S. riobravis [S. riobrave] TX strain and S. feltiae NF strain that had been recycled or stored at 5, 10, 15, 20 and 25°C. In all nematode strains, the unsaturation indices of total lipids increased as recycling or storage temperatures decreased. The unsaturation indices increased in the phospholipids of all strains except the TX strain of S. riobrave. Increased unsaturation indices at low temperatures was due to an increase in polyunsaturated fatty acids with concomitant decline in the proportion of saturated fatty acids, especially palmitic (16:0) and or stearic (18:0) acids. S. riobrave displayed a lower degree of physiological adaptation to cold temperatures than the other strains. The saturated fatty acids and unsaturation index of this nematode's phospholipid did not change in response to recycling or storage temperatures.

USA-TEMP & LIPIDS
3. MA-Abu-Hatab; Gaugler-R. 1997. Influence of growth temperature on fatty acids and phospholipids of Steinernema riobravis infective juveniles.
Journal-of-Thermal-Biology. 1997, 22: 4-5, 237-244; 23 ref.
AB: S. riobravis [S. riobrave] grew and reproduced over a wide temperature range (15, 20, 25 and 30°C) in Galleria mellonella. The lipid content of S. riobrave varied in amount and composition. PE and PC were the 2 major constitutive classes of polar lipids whereas triglycerols were the major constitutive classes of neutral lipids. Lipid content of nematodes grown at 15°C was marginally lower than at other growth temperatures. Nematodes accumulated higher proportions of saturated fatty acids when grown at high temperature (30°C). The ability of S. riobrave to adjust its lipid and fatty acid composition in response to growth temperature could contribute to thermal tolerance. It is recommended to culture S. riobrave at 25-30°C. At these temperatures more lipids are accumulated which may improve the physiological quality of S. riobrave compared to nematodes produced at lower temperatures (15-20°C). In addition, the growth and development cycle at high growth temperature in the insect cadaver is shorter compared to low temperature, which reduces the cost of mass production if applied in fermentation.

4. Gaugler-R; Grewal-P; Kaya-HK; Smith-Fiola-D. 2000. Quality assessment of commercially produced entomopathogenic nematodes. Biological-Control. 17:1, 100-109; 18 ref.
AB: The quality of Steinernema carpocapsae and Heterorhabditis bacteriophora products obtained by mail-order in the USA was assessed. Customer service provided by suppliers was generally satisfactory. All suppliers provided basic instructions, but 10% of shipments did not include this information. Two suppliers did not consistently have H. bacteriophora products available. Most companies gave recommendations on target pests that were judged to be highly accurate, but recommended application rates were less reliable. Cost varied greatly between suppliers. Two suppliers consistently shipped mixed species despite being asked for a specific species. The total number of nematodes tended to be lower than label claims (61.1% of expected numbers overall). The viability of nematodes received ranged from 81.1 to 99.3% for S. carpocapsae and 72.2 to 95.5% for H. bacteriophora. Pathogenicity to Galleria mellonella also varied between products.