With the pressure on margins leading to ever more intensive rotations, and the availability of effective chemical controls reducing, the risk of pests and diseases having a devastating economic impact on a farm business is growing. Many pests and diseases can multiply unnoticed in preceding crops with their presence only becoming apparent when their preferred crop e.g. Sugar Beet or Potatoes, becomes available. Catch crops can be targeted to reduce the impact of pests and diseases on high value crops, adding to the overall benefits such as improved soil structure, erosion control and weed suppression.
Beet Cyst Nematode
Species such as oil radish and mustard produce root secretions that induce nematode larvae to hatch quickly from cysts in the soil and migrate into the roots of the mustard and radish where they try to develop. In resistant mustard and radish varieties the nematodes have no source of nutrients and so die or develop into males, both actions resulting in a sharp decline in nematode numbers in the soil. To be really effective a deep rooting structure such as that of oil radish CONTRA (approx. 1.5m) is required as a large proportion of the nematode population is found at lower soil levels.
The objective of Bio Fumigation is to allow glucosinolates produced by species such as white mustard and oil radish to convert to isothiocyanates in the soil which can have a toxic effect on a range of nematodes, fungal diseases and weeds. In order to achieve this the bio fumigant crop must be finely chopped, incorporated and sealed into the ground to a depth of 15 – 20cm at a time when the crop's glucosinolates yields are at their highest (typically when 60-80% of the crop is in flower)
Free Living Nematodes (FLN)
A major problem in potato and carrot crops and a growing problem in cereals, especially on light sandy soils, where poor performance due to perceived drought or mineral deficiencies often has its prime cause as root damage caused by FLN’s. In other crops such as OSR or Maize the effects are more moderate but FLN’s can thrive and multiply in the presence of these crops exacerbating the problem for the following crop. As well as directly damaging the root system of crops, FLN ‘s can also act as a vector for plant pathogenic viruses spread by nematodes such as Trichodorous and Paratrichodorous spp. Spraing in potatoes is an example of such a disease which is caused by Tomato Rattle Virus (TRV) spread by Stubby Root Knot Nematodes. Depending on condition and species, FLN’s can survive for up to two years in the soil and can multiply by 5 – 1000 fold. Multi resistant oil radish varieties such as CONTRA can significantly reduce the population of a wide range of FLN’s such as Root Knot Nematodes & Root Lesion Nematodes.
Beet Cyst Nematode (BCN)
Heterodera schachtii (BCN) is a growing and persistent problem that represents arguably the main issue currently confronting Sugar Beet growers due to its potentially crippling yield losses. Unless infestation is severe and widespread, it can be difficult for a farmer to get an accurate picture of the BCN problem on their farm. As a result of potentially severe reductions in yield the impact of relatively small infestations can be economically significant. It has been independently demonstrated in Germany that varieties of oil radish such as CONTRA and CONCORDE, as well as white mustards such as VETO, can have a VERY significant impact on reducing BCN numbers. Growers can now choose BCN tolerant sugar beet varieties but these are unlikely to reduce BCN numbers to the extent of multi resistant radish varieties such as CONTRA. Including BCN tolerant catch crop varieties has been shown to significantly increase sugar beet yields and so represents the ideal precursor for BCN tolerant or non-tolerant varieties.
Plasmodiaphora brassicae is the causal agent for club root. In order to lessen the potential impact of this disease on OSR yields in particular it is important to select crops where possible that do not allow the disease to multiply. Phacelia and Saia Oats are NOT hosts for the Plasmodiophora parasite and as such are ideal catch crops for inclusion in OSR rotations in order to increase the overall output of crops in the rotation.
Potato Cyst Nematode (PCN)
PCN’s such as Globodera rostochensis and G. pallida spp. Can be a persistent and devastating problem for potato producers. Sticky Nightshade (Solanum sisymbrifolium) varieties such as White Star have the potential to very significantly reduce the population of PCN’s in the soil.
Rot and root decay can cause considerable damage in sugar beets and maize as well as affecting a wide range of other commercial crops. Tests in Holland have shown that multi resistant oil radish varieties such as CONTRA can have a positive effect on reducing infestations of Rhizoctonia.
Catch Crop Management and Selection
When applying agrochemicals, timing, application and product choice are crucial in achieving the best results possible for the conditions of the season and the state of the crop. The same principles apply to the use of catch crops. For example, in order to gain a good result against BCN, a suitable catch crop such as CONTRA should be sown into a warm moist soil when nematodes are active and hatching. A sufficient plant population should be established and the soil structure should be good enough to allow the development of a deep and effective root network to allow the crop to significantly reduce the BCN population. The rapid establishment of good ground cover will provide effective weed suppression which will help combat FLN’s and gall forming nematodes which can multiply in many weed species. A variety such as CONTRA with its rapid initial growth, delayed tendency to flower and long vegetative growth period will provide a broad window of operation against BCN.
Multi Resistant Fodder (Oil) Radish.
The performance of root crops such as Sugar Beet, Potatoes and other vegetable crops are affected by a range of nematodes and various crop rotation diseases. Multi resistant varieties such as CONTRA are the perfect addition to intensive rotations as they provide beneficial effects against a broad spectrum of threats. CONTRA also has strong bio fumigant properties which can provide an additional level of benefit to the overall crop rotation.
Resistance to Nematodes
CONTRA has excellent officially approved resistance against BCN (Heterodera schachtii ) and Root Knot Nematode (Meloidogyne chitwoodi) as well as having the ability to suppress Stubby Root Knot Nematode (Trichodorous & Paratrichodorous sp.) making the variety a very valuable inclusion to Sugar Beet, Potato, Vegetable and Bulb Rotations. CONTRA can also have a positive effect on the impact of Northern Root Knot Nematode (Meloidogyne hapla), Southern Root Knot Nematode (Meloidogyne incognita & m. javanica), Stem and Bulb Nematode (Ditylenchus dipsaci) and Root Lesion Nematodes (Pratylenchus)
Resistance to Diseases
As a result of its excellent ability to reduce Stubby Root Knot Nematodes which carry the TRV virus, CONTRA is a valuable tool in controlling Curly Ring Spot in potatoes. CONTRA also has a beneficial effect on reducing the impact of Rhizoctonia and Pythium as well as acting as a take all break.