Nematicides

Phosphorus compounds specially applicable as nematicides include (12.108). Nematicides and acaricides are in some cases classified as soil fumigants (see below). 

Some organophosphorus insecticides can be used to control animal ectoparasites by systanic action. They are sprayed on or fed to animals, after which they kill the insects (e.g. cattle grub) without harming the host. Compounds useful for this purpose include (12.109). Phosmet, bromofos and trichlorphon are also effective. 

In some cases, insect species can develop resistance to organophosphorus insecticides, and this resistance has appeared in those species most intensively attacked. Mixtures of insecticides are sometimes far more effective than the sum of the individual component toxicities when used separately. This effect is known as potentiation. The reasons for potentiation are not fnUy understood but they may be connected with the exhaustion of some metabolising enzyme by one insecticide, leaving the other insecticide to work freely. 

The correlation of insecticide structure with biological activity has received much attention althongh useful correlations are frequently confined to limited groups of compounds. The evolution of new insecticides is still to a large extent empirical. 

The generally higher toxicity of oxy compounds compared to their thio analogues has already been pointed out (e.g. paraoxon/parathion, malaoxon/malathion). Thiolo compounds are usually 

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Pesticide type H = herbicide I = insecticide SF = soil fumigate F = fungicide and N = nematicide. 

Lambert M, S Kremer, H Anke (1995) Antimicrobial, phytotoxic, nematicidal, cytotoxic, and mutagenic activities of 1-hydroxypyrene, the initial metabolite in pyrene metabolism by the basidiomycete Crinipellis stipitaria. Bull Environ Contam Toxicol 55 251-257. 

Structure of a second nematicidal principle isolated from Tagetes roots. Rec. trav. chim. 78, 382 (1959). 

Landels, S. (1989) Fumigants and nematicides. In Chemical Economics Handbook. Stanford Research Institute International, California. 

Thomason, I.J. (1987) Challenges facing nematology environmental risks with nematicides and the need for new approaches. In Veech, J.A. and Dickson, D.W. (eds) Vistas on Nematology. Society of Nematology, Hyattsville, Maryland, pp. 469-476. 

Chitwood D J (1992), Nematicidal compounds from plants , in Nigg H N and Seigler D, Phytochemical Resources for Medicine and Agriculture, Plenum Press UK, 185-204. 

In the family Fabaceae,8 CS2 production was investigated with 40 taxa of the subfamily Mimosoideae 29 produced CS2 and 18 produced COS (the latter was not formed in absence of CS2 production). CS2 production was less common in the subfamilies, Caesalpiniodeae and Papillonoideae. Since CS2 has a variety of bacteriostatic, fungicidal, nematicidal, and insecticidal properties, this production might deter soil pathogens. 

Condensation of coumaric acid with malonic acid yields the basic chalcone and stilbane skeletons (see Fig. 3.6). Stilbenes are found in most vascular plants, where they exhibit fungicidal and to a lesser extent antibiotic properties. They function as both constitutive and inducible defense substances. Some stilbenes inhibit fungal spore germination and hyphal growth, whereas others are toxic to insects and parasitic nematodes (round-worms). They also possess antifeeding and nematicide properties in mammals. For example, resveratrol (a stilbene in red wine) suppresses tumor formation in mammals. 

Anonymous. 1971. Furadan. Insecticide-Acaracide-Nematicide. Chemagro Corp. Kansas City, MO. 4 pp. 

Mathur, S.P., H.A. Hamilton, and T.C. Vrain. 1980. Influence of some field-applied nematicides on microflora and mineral nutrients in an organic soil. Jour. Environ. Sci. Health B 15 61-76. 

Since the first demonstration of soil solarization effectiveness against phytonematodes (Katan et al. 1976), nematicidal effects of solar heating were largely investigated on many genera of plant-parasitic nematodes. 

Giannakou IO, Anastasiadis IA, Gowen SR, Prophetou-Athanasiadou DA (2007) Effects of a nonchemical nematicide combined with soil solarization for the control of root-knot nematodes. Crop Prot 26 1644-1654. doi 10.1016/j.cropro.2007.02.003 Giblin-Davis RM, Verkade SD (1988) Solarization for nematode disinfestation of small volumes of soil. Ann Appl Nematol 2 41-5... 

Greco N, D Addabbo T, Stea V, Brandonisio A (1992) The synergism of soil solarization with fumigant nematicides and straw for the control of Heterodera carotae and Ditylenchus dipsaci. Nematol Medit 20 25-32... 

This comprehensive definition makes it elear that a wide number of substances may be eonsidered to be pestieides, and that the eommonality among all pestieides is their ability to provide eontrol over pests. A variety of classifications for pesticides have been developed that are specific for the type of pest controlled. Insecticides, for example, are pesticides that control insects, while herbicides control weeds and fungicides control plant diseases (molds). In addition to these major classifications of pesticides, there are many other classifications. These include nematicides (for nematode control), acaracides (mite control), rodenticides (rodent control), molluscicide (snail and slug control), algacides (algal control), bacteriocides (bacterial control), and defoliants (leaf control). 

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