Pesticides are fundamental to the way combinable crops are currently grown in the UK. They provide us with a relatively cheap and efficient way of controlling the major weeds, pests and diseases that affect combinable crops. These pesticides are currently under pressure as a result of changing legislation in Europe (revision of 91/414/EEC) and the implementation of the Water Framework Directive. Other pressures are also being applied in the form of increasingly resistant target organisms and the presence of pesticide residues in food products. These pressures are all leading to potential reductions in the availability of pesticides for the control of organisms harmful to plant health.
This report reviews the most important scenarios that could affect the availability of pesticides for use in wheat, winter barley, spring barley, oats and oilseed rape. It looks at the effects of the losses of pesticides on the weeds, pests and diseases they control and the resultant level of production and value that the crop could achieve.
ADAS experts determined the most important weeds, pests and diseases that affect each of the crops, and the proportion of crops affected by each. This was done through expert knowledge and the use of survey information. For each weed, pest or disease, plus lodging, estimates of total yield impact in business as usual and untreated situations were established, on an area weighted basis, using survey information and trials data supported by expert knowledge. ADAS experts then used their knowledge of the weed, pest or disease, supported by any relevant trials information to determine the effects of pesticide losses on yields in each of the scenarios.
It is uncertain as to exactly what the revision of 91/414/EEC will lead to as the final wording has not been agreed, although there are clear indications that the losses of pesticides will not be as severe as was once forecast. In this report a number of scenarios, based on a PSD report released in December 2008, were assessed to determine the effect on combinable crops. After a vote in the European Parliament (13th January 2009), it is likely that the least severe of the four PSD scenarios (scenario 2c) will be close to the final outcome, however, much will depend on final implementation. If this is the case it would result in the loss of about 23 active ingredients, of which only 20 are approved for use in the UK. Of these 20 active ingredients, 15 are used in the production of wheat, barley, oats or oilseed rape. Of the UK approved actives that are at risk 11 are fungicides, 6 herbicides, 2 insecticides and 1 rodenticide.
The greatest economic losses to cereals that occur as a result of scenario 2c are due to the loss of pendimethalin. This is a keystone of black-grass resistance management and also an important general herbicide. Although there are generally plenty of alternatives for broad-leaved weed control, the control of grass weeds, black-grass in particular, will become more difficult with resistance likely to become more of a problem. The loss of important triazole fungicides will make the control of foliar diseases such as Septoria and Yellow rust in wheat more difficult, as the remaining chemistry is not as robust as some of the active ingredients that will be lost. This will lead to slight reductions in production (about 1%). As relatively few insecticides are lost, and there are plenty of alternatives, the effect of this scenario on pests is minimal.
In oilseed rape the losses of pesticides to scenario 2c are unlikely to cause significant losses to production. There remain plenty of alternatives for the control of major weeds, pests and diseases.
It is not just the revision of 91/414/EEC that is likely to cause large scale losses of pesticide actives. The implementation of the Water Framework Directive (WFD) is likely to impact on a number of important active substances. The active substances that are most likely to be affected are those that are used on a large area and or used at high rates. This makes herbicides particularly vulnerable as large areas of combinable crops have high rates of active substance applied to them in the form of herbicides. As a result, about 10 herbicides are causing concerns with relation to the WFD. This includes a number of important actives for the control of grass weeds in oilseed rape (propyzamide, carbetamide and metazachlor). If restrictions or withdrawals for the use of these chemicals occur it could make the control of black-grass and other grass weeds almost impossible. If cropping systems remained the same, in affected areas, this could lead to yield losses similar to those seen in untreated crops of about 35%.
Oilseed rape is currently the main break crop used in cereal rotations. The herbicides that are available for the control of black-grass in rape have different modes of action compared to those that can be used in wheat. This makes the rape break crop a useful tool for cleaning black-grass infested fields prior to planting with cereals. This alternative chemistry is also an important part of the resistance strategy used to control black-grass. In the absence of effective herbicides in the break-crop, with alternative chemistry, there is the risk that herbicide resistance could develop more rapidly than at present and spread further. This therefore will lead to indirect losses of wheat and cereal yields as a result of resistance build-up.
Many of the insecticides are likely to be at risk from the WFD. As a result there could potentially be very limited options for the control of some pest species. At present, the level of pest infestation seen tends to cause minimal damage at an industry scale, the exception being aphids carrying virus and slugs. Slugs in particular could be difficult to control as metaldehyde is already under scrutiny because it is being found in water. If it is lost the area that is treated with methiocarb is likely to increase, putting it at similar risk of starting to appear in water. This could potentially leave growers with no good molluscicides for the control of slugs.
The loss of active substances to the WFD will be additional to any losses from the revision of 91/414/EEC. This could lead to larger impacts when combined as compared to when looked at in isolation.
Other reasons for loss of existing active substances include them failing to achieve Annex 1 listing before end December 2009, concern over residue levels in food or market acceptability, and development of resistance.
Under 91/414/EEC all active substances had to be reassessed for approval onto Annex 1. There are a number of active substances that are still going through this process. These substances have yet to provide sufficient data to meet the criteria required for inclusion in annex 1. Companies have until June 2009 to provide data for the active substances affected, or they will not be assessed. If they are not included in Annex 1 before end December 2010 they will cease to be approved. Notable active substances affected include a range of older grass weed herbicides, used in the control of volunteer cereals; metaldehyde, used for the control of slugs; and tefluthrin used as a seed dressing for wheat bulb fly control.
There are certain pesticides that are used on a wide range of crops in relatively high rates that are starting to show up in residue tests on certain food stuffs, e.g. glyphosate and chlormequat in cereals. If these pesticides continue to show up in food at levels that are considered unsafe then restrictions could be put on their use, but in any case there are pressures to reduce the levels found, such as through minimising use.
New products and options will become available. There are some new herbicides (ethametasulfuron), insecticides (indoxacarb, rynaxypyr, cyazapyr & spirotetramat) and fungicides (carboxamides) that are due to come on to the market within the next few years. Provided these pass the new approval requirements they will provide additional options for the control of charlock and cranesbill in OSR, Lepidoptera and sucking pests in a range of crops and additional boscalid like fungicides which are likely to provide extra control options for Septoria tritici. There are also some new breeding technologies being developed by BASF to produce non-genetically modified herbicide resistant crop plants. These are still in early development in North America with only limited crops available, the herbicide they are resistant to, imidazolinone, does not however give high levels of control of black-grass so would be of limited use in UK situations.
(For the full summary, including tables, please see attached complete review.)