Pesticides may cause problems when they seep out of storage or are washed out of the soil into waterways and groundwater. The chemicals are then diffused through the environment and may affect marine and bird life.
Agrochemical companies are registering new compounds that promise to tackle the pests already resistant to today's insecticides. BASF's metaflumizone works on the nervous system of target insects, blocking sodium channels to gradually induce paralysis. Dow's spinetoram is derived from spinosyn, a natural product that has insecticidal activity. Where Bayer's first two tetronic acid-based insecticides, spirodiclofen and spiromesifen, coat the leaf surface, new family member spirotetramat is actually taken up by the plant. The compounds work by inhibiting lipid biosysnthesis, affecting reproduction in adults and especially juveniles.
Significant adverse effects of imidacloprid have been reported on non-target beneficial invertebrates. Aquatic invertebrates (freshwater and estuarine/marine) are highly sensitive to imidacloprid.
Spirotetramat, a tetramic acid derivative (ketoenole), is a new insecticide that inhibits lipogenesis in treated insects, resulting in decreased lipid contents, growth inhibition of younger insects, and reduced ability of adult insects to reproduce. Although the intrinsic hazard potential to bees based on the acute oral and contact studies with honey bees appears to be low, brood feeding tests with bees and acute toxicity contact studies with other non-target insects (e.g. parasitoid wasps and predatory mites) conducted at less than the maximum application rate suggest there is potential for mortality in adults and pupae, massive perturbation of brood development, and early brood termination as a result of spirotetramat use.
A recent study indicates high toxicity of imidacloprid to the non-target terrestrial arthropod P. scaber when compared to birds and mammals. Imidacloprid affects isopods at similar exposure concentrations as insects.
The new GABA-disrupting insecticide fipronil may pose a high risk to copepod production in estuarine systems. Copepods are the most abundant arthropods on earth and often the most important secondary producers in estuarine/marine food webs.
Imidacloprid can be applied as a systemic insecticide to trees by direct stem injections or by soil injections and drenches, and be indirectly introduced to aquatic systems via leaf fall or leaching, which may pose a risk to natural decomposer organisms. When applied directly to aquatic microcosms to simulate leaching from soils, imidacloprid was shown to be highly toxic to aquatic insects. Imidacloprid at realistic field concentrations in maple leaves had adverse effects on aquatic insects and earthworms. Imidacloprid at realistic concentrations in leaves can inhibit leaf litter breakdown through adverse effects on decomposer invertebrates. When imidacloprid is applied as a systemic insecticide to the soil around trees it may cause adverse effects on earthworms.
A quarter of the total UK landmass (6,000,000 ha) received annual treatment with insecticides between 1990 and 2003. The overall weight of active ingredients used has declined due to newer compounds with greater intrinsic insecticidal activity.
The effect of a single pulse contamination with the neonicotinoid insecticide thiacloprid on invertebrates was investigated in mesocosms designed to realistically mimic communities in small streams within the agriculural landscape. The contamination resulted in long-term alteration of the overall invertebrate community structure. One species, the stonefly Nemoura cinerea, was affected at the lowest tested concentration, 70 times below the lowest known median lethal concentration (LC50).
A study identified two factors that may limit breeding productivity of the Reed Bunting Emberiza schoeniclus, which is in significant decline in England since the 1990s: ground vegetation providing concealment from nest predators and availability of invertebrate prey for chicks. The increased use of pesticides may have reduced invertebrate densities on most farmland.