Crops(s) Wide host range of plant species
IRAC Nematode Working Group – Nematicide Mode of Action Classification
Nematicide Resistance Risk statement
There are no substantiated examples in the scientific literature from the last century documenting cases of significant tolerance shifts or suspected resistance leading to failure of commercial agricultural nematicides against plant parasitic nematodes (PPN) under natural field conditions. Instances of these phenomena occurring have only been reported for some products under controlled laboratory conditions(1). Product usage approaches and nematode ecology also reduce the potential that sustained selection pressure on PPN populations occurs under field conditions. Thus overall, it can be considered that the development of resistance in PPN species to nematicides under natural field conditions is currently unconfirmed, theoretically unlikely, and poses a low risk.
The reasons underpinning this conclusions are explained below:
Unlike other plant protection products (e.g. herbicides, fungicides and insecticides), several factors limit the potential for nematicides to create high and sustained selection pressure on plant parasitic nematode (PPN) populations under field conditions:
These factors include the:
Plant parasitic nematodes occur in a variety of pressures (soil population density levels) under field conditions. In some countries, and in some species, local threshold levels may be available to assess the risk of economic crop loss. Nematode management programs should be used in cases where populations of PPNs are deemed high or very high, employing multiple tactics to provide effective control and population reduction. These programs may include cultural practices e.g. crop rotations or fallow periods, solarization, nematode resistant or tolerant varieties and the application of nematicides. In cropping systems which require multiple nematicide applications within one crop cycle or on the same field over several cycles, rotation to a nematicide with a different mode of action is recommended to reduce the risk of sustained selection pressure on PPN populations.
Nematicidal products with fungicidal or insecticidal activity require additional resistance management considerations and labelling according to FRAC or IRAC guidelines.
Reduced performance of chemical nematicides can be caused by the phenomenon of Enhanced Microbial Biodegradation (EMB)(2). This is well documented in the scientific literature and EMB should not be confused with resistance development in plant parasitic nematodes. EMB affects the level of product availability and duration of exposure of PPNs to the product, thus reducing the apparent efficacy of a nematicide application. Rotation of nematicides from different chemical classes, as well as employing other control methods such as resistant varieties and cultural methods (e.g. crop rotations) should be considered.
(1) Tolerance shifts or resistance development in PPNs under laboratory conditions:
Although few cases have been reported, continuous exposure to sub-lethal levels of a single nematicide or mode of action may lead to the development of resistant populations under laboratory conditions. This however cannot be extrapolated to field conditions.
(2) Enhanced microbial biodegradation (EMB):
Repeated or frequent use of the same chemical nematicide in the same field soil may lead to an apparent reduction in PPN control through enhanced microbial biodegradation (EMB) of the product. EMB is the result of adaptation and increase of microbial populations that break down a particular product, therefore changing the amount of product available and/or duration of exposure of PPN’s. The microbes responsible for EMB in soil may be different for different chemical classes or products, thus rotation of different nematicide types, or a reduction in the frequency of applications may decrease the likelihood of EMB occurrence.
Key to targeted physiology:
The colour scheme provides a key to targeted physiology and not for resistance management purposes. Rotations for resistance management should be based only on the numbered MoA groups.
|Nerve and muscle|
|Growth and Development|
|Unknown or Non-specific|
|N-1||Acetylcholinesterase (AChE) inhibitors
(Only major representatives of the groups are shown)
|Aldicarb, Carbosulfan, Carbofuran, Thiodicarb, Oxamyl, Benfuracarb|
|Fenamiphos, Terbufos, Imicyafos, Ethoprofos, Fosthiazate, Cadusafos, Phorate|
|N-2||Glutamate-gated chloride channel (GluCl) allosteric modulators||Abamectin|
|N-3||Mitochondrial complex II electron transport inhibitors. Succinate-coenzyme Q reductase||Fluopyram, Cyclobutrifluram|
|N-4||Lipid synthesis, growth regulation. Inhibitors of acetyl CoA carboxylase||Spirotetramat|
|N-UN||Unknown||Furfural, Fluensulfone, Fluazaindolizine, Iprodione|
|N-UNX||Volatile sulfur generator||Carbon Disulfide, Dimethyl Disulfide (DMDS)|
|Carbon disulfide liberator||Sodium tetrathiocarbonate|
|Alkyl halides||Methyl Bromide, Methyl Iodide (Iodomethane)|
|Halogenated hydrocarbon||1,2-Dibromo-3-chloropropane (DBCP), Ehtylene Dibromide, 1,3-Dichloropropene|
|Methyl isothiocyanate generator||Dazomet, Metam Potassium, Allyl isothiocyanate, Metam Sodium|
|N-UNB||Burkholderia spp. E.g. rinojensis A396, Bacillus spp. e.g. firums, subtilis, Streptomyces spp. e.g. lydicus, dicklowii, albogriseolus, Pasteuria spp. e.g. penetrans, nishizawee, Pseudomonas spp. e.g. chlororaphis, fluorescens|
|N-UNF||Arthrobotrys spp. e.g. oligospora, Muscodor spp. e.g. albus, Pochonia spp. e.g. chlamydosporia, Myrothecium spp. e.g. verrucaria, Paecilomyces spp. e.g. lilacinus (syn Purpureocillium lilacinum), carneus, fumosoroseus, Actinomyces spp. e.g. streptococcus, Trichoderma spp. e.g. harzianum, virens, atroviride, viride, Aspergillus spp. e.g. niger|
|N-UNE||Azadirachtin, Quillaja saponaria extract, Camellia Seed Cake, Terpenes, e.g. Carvacrol, Chitin, Garlic extract, Essential oils, Pongamia oil|
|Indemnify Turf Nematicide||Fluopyram||N-3|
|Nimtz 180 EC Nematicide||Fluensulfone||N-UN|
Content last updated: July 14, 2023