Providing evidence to improve practice

Action: Use crop rotation in potato farming systems Natural Pest Control

Key messages

Pests: Nine studies from Canada and the USA, and one review, investigated the effect of crop rotation on pest or pathogen populations in potato. Three studies (including two replicated studies of which one randomised and one controlled) and a review found crop rotation reduced pest populations and crop diseases in at least one year or at least one site. One paired study (including one replicated, randomised, controlled trial) found pest populations increased in crop rotation. Four studies (including one replicated, randomised, controlled trial) found increases and decreases in pest populations depending on rotation crops used and other treatments. One replicated, randomised, controlled study found no effect.
Yield: Three out of five studies (all replicated, controlled, two also randomised) from Canada and the USA, found that crop rotation increased crop yield in some years or with certain rotation crops. The two other studies (both replicated, one also randomised and one replicated) found yield increases and decreases depending on rotation crops used.
Profit: One replicated, controlled study found that crop rotation increased profit.
Insecticides: Two studies (one replicated, controlled) found that fewer insecticide treatments were needed on rotated plots.

Crops studied were alfalfabarleybroccoli, brown mustardbuckwheatcottonlupinsmaizeoats, pearl milletpeaspotato, rye, sorghumsoybean, sugar beet, timothy grass, wheat and yellow sweet clover.

Supporting evidence from individual studies

1 

A paired sites study in 1982-1983 on Long Island, New York, USA (Wright 1984) found that on five of seven pairs of sites, density of early season adult Colorado potato beetles Leptinotarsa decemlineata (pest) was reduced by 95.8% in 1982 and by 69.5% in 1983 in fields that were rotated to rye Secale cereale in the previous year, compared to fields that had been planted with potatoes Solanum tuberosum for two consecutive years. In the other two pairs of sites, potato beetle numbers were low in both rotated and non-rotated fields. Under an integrated pest management scheme, non-rotated fields required an average of one additional insecticide spray over the growing season, and in three pairs of fields crop damage was significantly lower in the rotated field. The experiment used pairs of rotated and non-rotated fields on four farms in 1982 and five in 1983. Fields averaged 8 ha in size and were up to 2 km apart. Colorado potato beetle densities were monitored weekly from late May. Densities were estimated by counting beetles on 80 potato stalks in 1982 and 50 stalks in 1983.

 

2 

A paired sites study in 1982-1983 on Long Island, New York, USA (Leach et al. 1986) found that potatoes Solanum tuberosum in fields that had been rotated to barley Hordeum vulgare the previous season had 1.6 times more pest lesion nematodes Pratylenchus spp. per gram of root as fields that had grown potatoes in both seasons (395 nematodes/g potato root vs. 251 for non-rotated fields). Nematode soil populations were 1.4 times higher in rotated fields (376 nematodes/100 cm³ vs. 274 for unrotated fields). Data from the same experiment on Colorado potato beetle Leptinotarsa decemlineata numbers is described in Wright (1984). The experiment used pairs of rotated and non-rotated fields on four farms in 1982 and five in 1983. Fields averaged 8 ha in size and were up to 2 km apart.

 

3 

A randomised, replicated study in 1983-1987 on Prince Edward Island, Canada (Kimpinski et al. 1992) found more root lesion nematodes Pratylenchus penetrans (pest) in barley Hordeum vulgare after one year of soybean Glycine max (3,240 nematodes/g root and 4,170 nematodes/kg soil) than after potato Solanum tuberosum, wheat Triticum aestivum, or two years of continuous barley (630-780 nematodes/g root and 1,260-1,700 nematodes/kg soil). Barley yields were highest after potato (3,514 kg/ha), followed by soybean (3,293 kg/ha), wheat (3,195 kg/ha) and continuous barley (2,712 kg/ha). In soybean after barley, nematode density and yield did not change according to crops two years before. In the final study year, nematode density did not vary between plots, but potato yield was lower in plots that had grown potato or soybean three years before. Crops were grown in randomised 10 x 32 m plots, in a field planted with barley the previous year. Each rotation pattern was replicated six times. Plots grew barley, wheat, soybean or potato in 1984, barley or potato in 1985, soybean in 1986 and potato in 1987. Seeding rates, fertilizer, pesticide and herbicide use followed standard practice for the region.

 

4 

A 1992 review on plant-parasitic nematodes (Nematoda) (Wolny 1992) found that crop rotations with low proportions of nematode host plants generally prevented nematode (pest) population build-up in soils. No sugar beet cyst nematodes Heterodera schachtii were found in a rotation where sugar beet Beta vulgaris was grown for one year out of six with other rotation crops that were non-hosts, but nematodes were found when sugar beet was grown at a higher frequency. No potato cyst nematodes Globodera rostochiensis were found in a five year rotation with one year of potato Solanum tuberosum followed by four years of non-host crops, but the nematode was present with two years of potato and present with increasing population density with three years of potato in every five. Population densities of cereal cyst nematode Heterodera avenae were low in rotations with 25 or 50% oats Avena sativa or rye Secale cereale (0-58 eggs and larvae/100 cm³ soil) but generally higher with 75% (9-280 eggs and larvae) or 100% oats or rye (29-920 eggs and larvae) although populations remained low at some sites growing rye. The review covered 23 studies, mostly from Eastern Europe.

 

5 

A study in 1987-1990 in arable land in Presque Isle, Maine, USA (Leach et al. 1993) found that under moldboard ploughing, incidence of Rhizoctonia solani disease in potatoes Solanum tuberosum was 91% higher than average in rotation with oats Avena sativa, but did not vary with four other rotation crops: buckwheat Fagopyrum esculentum, lupins Lupinus albus, peas Pisum sativum and broccoli Brassica oleracea. Under chisel ploughing, R. solani was 83% lower than average in rotation with broccoli but was not affected by rotation with oats, buckwheat, lupin or peas. No differences between rotation crops were observed until the fourth year of the study. Rotation crop showed no effect on R. solani soil populations. The five rotation crops were planted in two year rotations with Russet Burbank potatoes. Rotation plots were 8.6 x 20.1 m, with 4.3 x 20.1 m subplots under each ploughing treatment. All rotation crops were harvested except buckwheat, which was ploughed in as a green manure. Ten weeks after planting, 10 plants from each potato plot were scored for R. solani incidence and twenty-five 20 cm deep soil samples were taken to assess soil populations.

 

6 

A randomised, replicated, controlled study in 1989-1991 in Michigan, USA (Chen et al. 1995) found that potato Solanum tuberosum yield was significantly higher in fields that had grown alfalfa Medicago sativa (32.3 t/ha) or yellow sweet clover Melilotus officinalis (33.8 t/ha) in the previous two years than fields that had grown potatoes for three years continuously (22.8 t/ha). Yield of potato in rotation with one year of rye Secale cereale, one or two years of maize Zea mays and one or two years of a sorghum hybrid Sorghum halepense x sudanense was not significantly different to continuous potato. Populations of wilt fungus Verticillium dahliae and root lesion nematode Pratylenchus penetrans were not affected by crop rotations. The experiment used five replicates of ten rotation treatments. Plots were 15 m long and four crop-rows wide. Crop management followed local recommendations for conventional potato production. Wilt fungus and root lesion nematode were sampled at the beginning, middle and end of each growing season using eight to twelve 600 cm³ soil cores in each plot.

 

7 

A replicated, controlled study in 1994-1996 in Virginia, USA (Speese & Sterrett 1998) found that potatoes Solanum tuberosum grown in 1995 in plots rotated with wheat Triticum sp. or double-cropped wheat and soybean Glycine max in 1994 had lower Colorado potato beetle Leptinotarsa decemlineata (pest) populations and 47% higher yields in 1995 (22.52 vs. 15.34 t/ha) than plots where potatoes were grown in 1994. In 1996, Colorado potato beetle populations were much smaller and not significantly different between plots rotated with cotton Gossypium sp. or left fallow and non-rotated plots. In both years, more insecticide sprays were required in non-rotated plots, and in 1995 rotated plots had a return of US$2,342.50/ha compared to US$552.50/ha for non-rotated plots. The experiment used 7.6 m long, three row wide plots in 1994-1995 and 6.1 m long, four row wide plots in 1995-1996. In 1994 rotation crops were wheat or wheat-soybean double crop, and in 1995 rotation crops were cotton or fallow. Unrotated control plots were replicated four times, whilst each rotated plot  was replicated twice. Rotated and non-rotated plots were a minimum of 150 m apart. Insecticides were applied based on threshold beetle numbers.

 

8 

A randomised, replicated study in 1999-2003 in Maine, USA (Alyokhin et al. 2005) found that numbers of Colorado potato beetle Leptinotarsa decemlineata larvae were not significantly different between a two-year rotation (potato Solanum tuberosum-barley Hordeum vulgare), an intensive four-year rotation (potato-soybean Glycine max-potato-barley) and an integrated four-year rotation (potato-soybean-barley-alfalfa Medicago sativa/timothy Phleum pratense) except in the final year of the experiment when the two-year rotation had significantly more large larvae (1.72 larvae/plant), compared to the integrated four-year rotation (1.51) and the intensive four-year rotation (1.45). The experiment used 96 plots, each 41 x 14.6 m, split into four blocks. Rotation treatments were randomised within each block. Imidacloprid was used for pest control on all plots as part of an integrated system, with thresholds for spraying of one adult, eight small larvae or three large larvae/plant.

 

9 

A replicated, controlled trial in 2001-2002 at L'Assomption, Quebec, Canada (Dauphinais et al. 2005) found that density of root lesion nematode Pratylenchus penetrans (pest) was significantly higher after rotation of potatoes Solanum tuberosum with rye Secale cereale (8533 nematodes/kg soil) than after rotation with grain pearl millet Pennisetum glaucum (867 nematodes/kg soil) or continuous potato cultivar Superior (467 nematodes/kg soil). In the following growing season yields of potato cultivar Superior were lower in rye plots (10.8 tons/ha) than in grain pearl millet plots (24.1 tons/ha) or in continuous potato plots (21.8 tons/ha). Yields of potato cultivar Hilite Russet varied less between rotation crops. The experiment was carried out in four plots that had all grown potatoes in 2000. Each plot had one strip of each treatment. Strips were 10 x 80 m. Grain pearl millet was sown at 5.8 kg/ha with 230 kg/ha N in the form of 19-19-19 NPK fertilizer. Rye was sown at 120 kg/ha and potato planted at 2,313 kg/ha. In 2002 half of each strip was planted with each of the two potato varieties and yield was recorded. Nematodes were monitored twice each year using twelve 20 cm deep soil cores/strip.

 

10 

A randomised, replicated, controlled study in 1998-2003 in arable land in Quebec, Canada (Belair et al. 2006) found that population density of root lesion nematodes Pratylenchus penetrans (pest) was consistently low in autumn following forage pearl millet Pennisetum glaucum cultivar CFPM 101 (11-430 nematodes/kg soil) and generally low following grain pearl millet Pennisetum glaucum cultivar CGPM H-1 (94-2,297 nematodes/kg soil) compared with other crops. Nematode population densities tended to be high in autumn after brown mustard Brassica juncea (1,800-5,735 nematodes/kg soil), maize Zea mays (2,043-2,467), oats Avena sativa (3,997-6,353), potato Solanum tuberosum (3,257-6,365), rye Secale cereale (3,753-9,728) and soybean Glycine max (1,398-4,768). After soybean nematode population densities were low the following spring (73-300/kg soil), whereas for after other crops they remained high. Marketable potato yield in the fourth year of the experiment was highest after three year rotations ending in forage or grain pearl millet (38.4-55.9 t/ha) and lower with other final rotation crops (23.5-43.0 t/ha). The study had 14 different three year rotation treatments, each of which was applied at random to eight replicate 1 x 2 m plots. In the fourth year, potatoes were grown in all plots. Fertilizers, pesticides and irrigation followed local standard practice and weeds were removed by hand.

 

Referenced papers

Please cite as:

Wright, H.L., Ashpole, J.E., Dicks, L.V., Hutchison, J., McCormack, C.G. & Sutherland, W.J. (2017) Some Aspects of Enhancing Natural Pest Control. Pages 359-381 in: W.J. Sutherland, L.V. Dicks, N. Ockendon & R.K. Smith (eds) What Works in Conservation 2017. Open Book Publishers, Cambridge, UK