The main purpose of quantitative nematological research is to achieve an optimal economical protection of crops against plant-parasitic nematodes. To accomplish this, the costs of control measures must be adjusted to the costs of the expected yield reduction compared to the yield in a situation without the need for control. Such an adjustment requires quantitative knowledge of: (1) the relationship between a measure for the nematode activity (in practice mostly their population density at the time of planting) and plant response; (2) the population dynamics of nematodes in the presence of food sources (of different quality) and in the absence of food; (3) the effect of control measures on plant response and nematode population dynamics; the control measures may range from pesticide treatment, crop rotation and cultivation of crops that vary in suitability as a food source for nematodes; and (4) cost/benefit of the control measures. Some of these aspects are discussed in this chapter.

As part of developing a routine potato cultivars resistance test to Meloidogyne chitwoodi , both the effect of nematode density ( P i) and pot size on growth, tuber yield, quality and tuber infestation level were studied in glasshouse conditions. The study was carried out in four experiments using cv. Desiree as control and seven genotypes with a single resistance gene to M. chitwoodi and 1 genotype, with resistance to Globodera pallida . Plants were inoculated with ranges of P i from 0.0625 to 256 J2 (g dry soil) −1 in log series. Haulm height, tuber yield, starch dry matter content (SDC) and tuber quality were recorded. Additionally, harvested tubers of experiment 2 were stored for 240–300 days to estimate actual tuber infestation at planting when used as seed in a subsequent season. Haulm height was positively affected with increasing P i’s and negatively with decreasing pot size. The yield was not affected in four out of seven genotypes with resistance to M. chitwoodi ; they can be considered as tolerant, having a relative minimum yield, m = 1. Three genotypes and cv. Desiree showed relative minimum yield, m < 0.8, the latter varying between 0.67 and 0.80 over experiments and pot sizes. The reduction of SDC equalled that of yield indicating that M. chitwoodi had no extra effect on starch content. Quality, expressed as tuber-knot index (TKI), used for accepting ware potatoes for processing, was below 10 for all genotypes, except for 2011M1. The TKI values of cv. Desiree and genotype MDG2 were > 20 and are not accepted for processing. The fraction of clean tubers of the resistant genotypes had significantly increased to 91% compared to < 8% for cv. Desiree and MDG2. Tuber infestation, expressed to number of juveniles per gram dry soil of cv. Desiree after storage, showed no regression with the P i and averaged 0.35 J2 (g dry soil) −1 , while all tested genotypes provided ca . 0.002 J2 (g dry soil) −1 .

The development of the Akkerweb service platform ( https://akkerweb.eu ) was started around 2010. It is an open platform in precision farming, providing the maps, services, data, and connections required, in principle, for any smart farming application envisioned. This includes background maps, services for weather data, satellite images, soil maps, crop polygons, etc., but also visualization tools, an app store, a task map generator, and crop growth models. Akkerweb provides the infrastructure needed to develop an application easily using the available services and to publish it on the Akkerweb platform. Moreover, Akkerweb applications can also run on other websites, seemingly as stand-alone applications with the look and feel of the customer's website. A unique point of the Akkerweb service platform is the availability of several science-based agronomic models which are currently made available as APIs for use in smart farming applications. Examples of these models are those to calculate water availability (Watbal model), potato crop growth (Tipstar model), late blight infection (Blight module), and nematode management (Nemadecide) at individual field and within-field levels. Other models are available for variable-rate application of soil herbicides and fungicides against blight, nitrogen top-dress application in potato and potato haulm killing. In total, Akkerweb has more than 30 apps. farmmaps ( https://farmmaps.eu ) is the next version of Akkerweb. It has a new data repository and management system as well as a new, more intuitive dashboard design running on all devices. It became available first in 2021.

High population densities of the potato cyst nematodes (PCN) Globodera pallida and G. rostochiensis cause substantial yield losses to potato production (Solanum tuberosum) due to the delay caused to tuber formation by the retardation of plant growth. It requires meticulous estimation of the population densities by using soil sampling and applying the right combination of nematode management to deal with the PCN problem. This study aims to assess the use of an unmanned vehicle (UAV) in detecting and estimating the effect of ranges of densities of a PCN, G. pallida, on four cultivated potato cultivars with resistance to PCN in a naturally infested potato field in The Netherlands. First, the initial population density (Pi) of G. pallida was estimated by using an intensive sampling method of collecting about 1.5 kg of soil per m2 from the center of each 3 × 5 m plot. At harvest, the fresh tuber yield of the potato cultivars (Avarna, Fontane, Sarion, and Serresta) were assessed. The Seinhorst yield loss model was used to investigate the relationship between Pi and fresh tuber yield. Secondly, the spatial data of UAV with optical and thermal sensors were analyzed to find any relationship between Pi and UAV indices. By using the classical yield loss model, all four cultivars were found to be affected by Pi with a relative minimum fresh tuber yield m, which ranged from 0.26 to 0.40. The maximum fresh tuber yield varied from 49.48 to 80.36 tons (ha)−1. The density at which the fresh tuber yield started to deteriorate was in the range of 0.62–2.16 eggs (g dry soil)−1. A regression was observed between Pi, and all UAV indices in a similar pattern to that of the fresh tuber yield by using the Seinhorst yield loss model, except for the cultivar Avarna for the two UAV indices (NDRE and NDVI). Unlike the tolerance limit, the relative minimum values of the UAV indices—except the chlorophyll index—differ when compared among each other and when compared with that of the fresh tuber yield within the same cultivar. This indicates that all indices can be useful for detection and decision making for statutory purposes but not for estimating damage (except the chlorophyll index).

Phytophthora infestans causes late-blight in potatoes. Without control P. infestans causes severe damage to the foliage and tubers, leading to yield loss. A way to suppress the disease without chemical control would be to remove the primary inoculumm sources originating from infected seed tubers or oospores in the soil. These latently diseased plants, if detected before symptom expression and sporulation, could be removed. To do so early detection is required. A pot-experiment to detect latent late blight using hyperspectral imaging was conducted. Several inoculation rates and both spray inoculation and point inoculation were used. The spectral signature of the soon to die tissue was learned which enabled early detection of latent potato late blight, well before it was detectable by a trained human eye.

The development of the Akkerweb service platform was started around 2010. It is an open data platform for precision farming, providing maps, services, data, decision support and connections required for, in principle, any precision farming application envisioned. This includes background maps, services for weather data, satellite images, soil maps, crop polygons, etc., but also visualisation tools, a store, a task map generator and crop growth models. Akkerweb provides the infrastructure needed to easily develop an application using the available services and publish it on the Akkerweb platform. Moreover, Akkerweb applications can also run on other websites, seemingly as standalone applications with the look and feel of the customer's website. Akkerweb/FarmMaps have decision support tools for soil moisture and crop growth monitoring, nitrogen top dress application, potato haulm killing and late blight control in potatoes. Irrigation, soil herbicide use and nematode management in arable crops on Akkerweb/FarmMaps are presented. Results of use of the decision support in on-farm research are given.

Experiments were carried out in 2012 and 2013 to answer two basic questions in the testing of potato blackleg causing agents before and after harvest. Firstly, what is the spatial distribution of symptomatic plants in the field. Secondly, what is the distribution of infected tubers over the crates and the resulting detection probability using the standard method of collecting 200 tubers from the top crates in storage. In both years, ten farmers were equipped with a global positioning system (Garmin GPSMAP 62) and asked to register the position of blackleg diseased plants every time they scouted their potato lot for diseases. To answer the second question, potatoes marked with four nails (only visible internally after harvest) and potatoes with a different skin colour were added to one-hectare (ha) fields of seed potatoes in different patterns of aggregation ranging from random, to aggregated distribution, up to one big hotspot prior to harvest. The invisibly marked tubers were used for the unbiased collection of twenty 200-tuber samples from the storage crates, while the coloured skin tubers were used to ascertain, when the potatoes were graded, the distribution of ‘infected’ potatoes over the storage crates. The experiment was carried out with 0.05 and 0.1% disease incidence, in 2012 and 2013, respectively. Twenty two out of 26 fields proved to have a random pattern of diseased plants at harvest, which indicates that the blackleg diseased plants came into the field as infected seed potatoes. Two of the four aggregated patterns detected, started out as random distributions but became aggregated later in time, indicating spread in the field. A random spatial pattern in the field at harvest proved to result in a uniform distribution of infected tubers in the crates and, consequently, sampling of only the top crates for the 200-tuber sample does not introduce any bias. Fifty percent of the infected farmer lots were detected by the Nederlandse Algemene Keuringsdienst inspectors performing their official field surveys, which was a better performance than the 18% detection obtained by the standard 200-tuber sampling method. Only 6 out of 80 samples from the ‘infected’ lots with 0.05% disease incidence level, and 22 out of 80 samples at the 0.1% disease incidence level were detected by the latter method. It was concluded that intensifying the field survey would be cheaper and more successful than enlarging the tuber sample size to increase the probability for detection of infected seed lots.

The Digital Future Farm (DFF) is a modeling framework that allows models of arable and dairy farms to be assembled from sub-models such as crop, soil and livestock models. The DFF is also a digital twin (DT): a model of a physical object with emphasis on (1) the connection between the real-world object and its virtual counterpart and (2) the use of real-time data from sensors to keep the model synchronized. In this study, an Ensemble Kalman Filter was used to synchronize a grass model and a potato model in the DFF with observations made in experiments. Results indicate that special care must be taken to prevent divergence of the Ensemble Kalman Filter when it is used with a crop growth model.

Large farmers’ datasets can help shed light on agroecological processes if used in the context of hypothesis testing. Here we used an anonymized set of data from the geoplatform Akkerweb to better understand the correlation between within-field elevation and normalized differential vegetation index (NDVI, a proxy for biomass). The dataset included 3249 Dutch potato fields, for each of which the cultivar, the field polygon, the year of cultivation and the soil type (clay or sandy) was known. We hypothesize that under dry conditions such correlation is negative, meaning that the lowest portions of the field have more biomass because of water redistribution. From the data, we observed that in dry periods, such as the summer of 2018, the correlation was negative in sandy soils. Furthermore, we observed that early cultivars show a weaker correlation between NDVI and elevation than late cultivars, possibly because early cultivar escape part of the long dry summer spells. We conclude that the correlation between NDVI and elevation may be a useful indicator of drought stress, and deviations from the norm may be useful to evaluate the resistance to drought of individual cultivars.

Summary The population densities of Meloidogyne chitwoodi in potato tubers stored at 4, 8 and 12°C after 0, 60, 120, 180 and 240 days of storage were assessed. Compared to day 0, storage temperatures of 4 and 8°C reduced population densities to 9 and 35%, respectively, after 240 days of storage, while nematode numbers in tubers stored at 12°C increased 2.5 times. The maximum hatching rate of nematodes from tubers stored at 8 and 12°C increased linearly with storage time. At 4°C it remained constant. The time required for the hatching process to reach the maximum number of second-stage juveniles (J2) decreased with increasing storage temperature. Recovered juveniles of M. chitwoodi from tubers after 180 and 240 days of storage at all three temperatures were still infective and able to multiply on ‘Desiree’ with estimates of the maximum multiplication rate (a) and the maximum population density (M) of 63.6 and 70.8 J2 (g dry soil)−1, respectively.

Relative tuber infestation and quality of two Meloidogyne chitwoodi resistant potato genotypes, AR04-4096 and 2011M1, were compared in glasshouse experiments at initial population density () = 16 second-stage juveniles (g dry soil)−1 in the presence and absence of the bristle oat, Avena strigosa. When A. strigosa was added, ( final population) on both AR04-4096 and 2011M1 increased 130×, increased 1.9 and 3.7×, respectively, while × fresh root weight (FRW)−1 was the same. Nematode hatch from peel of AR04-4096, without A. strigosa, was delayed by 3 weeks but relative hatching rate was increased. Although the RStuber (RS = Relative Susceptibility) of both AR04-4096 and 2011M1 were lower than 1%, in the presence of A. strigosa tuber quality of 2011M1 dropped below the marketable level, while that of AR04-4096 was hardly affected. We conclude that: i) is influenced by root mass; ii) root quality influences nematode hatch; iii) tuber quality is not an estimator for tuber resistance, and the reverse; iv) root resistance is equal to tuber resistance.

Precision agriculture is a farming management concept based on observing, measuring and responding to inter- and intra-field variability in crops. In this paper, we focus on responding to intra-field variability in potato crops and analyse variable rate applications (VRAs). We made an overview of potential VRAs in potato crop management in The Netherlands. We identified 13 potential VRAs in potato, ranging from soil tillage to planting to crop care to selective harvest. We ranked them on availability of 'proof of concept' and on-farm test results. For five VRAs, we found test results allowing to make a cost-benefit assessment. These five VRAs were as follows: planting, soil herbicide weed control, N side dress, late blight control and haulm killing. They use one of two types of spatial data: soil maps or biomass index maps. Data on costs and savings of the VRAs showed that the investments in VRAs will pay off under practical conditions in The Netherlands. Savings on pesticide use and N-fertilizer use with the VRAs were on average about 25%, which benefits the environment too. We foresee a slow but gradual adoption of VRAs in potato production. More VRAs will become available given ongoing R&D. The perspectives of VRAs in potatoes are discussed.

Yield and quality loss of carrot (Daucus carota L. cv. Nerac) caused by Pratylenchus penetrans and the population dynamics of this nematode were studied in a climate controlled glasshouse. A range of 12 nematode densities was used at three different seed densities of carrot; 2, 4 and 18 seeds pot−1. Seinhorst’s yield loss model; y = m + (1 - m) 0.95 Pi/T-1 for Pi > T; y = 1 for Pi ≤ T for Tylenchina was fitted to the yield and quality loss data. Seinhorst’s model for population dynamics of migratory nematodes with multiple generations; \( Pf=M* Pi/\left( Pi+M/a\right) \) was fitted to the data of the final population densities (Pf). P. penetrans had a significant impact on carrot taproot yield and its quality. The tolerance limits for the relative carrot taproot yield (T y) were 1.51, 1.88, and 1.37 and those of quality yields (T q) were 0.67, 0.18, and 0.40 P. penetrans (g dry soil)−1 at 2, 4 and 18 seeds pot−1, respectively. Both the minimum yield (0.20, 0.29, and 0.60) and the minimum quality yield (0.05, 0.07, and 0.20), expressed as a proportion, increased with seed density at 2, 4 and 18 seeds pot−1, respectively. The model for population dynamics fitted well to the Pf data obtained. The maximum multiplication rates (a) were 19.58, 9.99, and 17.54, while the maximum population densities (M) were 49.86, 43.21, and 60.37 P. penetrans (g dry soil)−1 at 2, 4, and 18 seeds pot−1, respectively. Carrot cv. Nerac can be considered a good host for P. penetrans.

The population dynamics of Meloidogyne chitwoodi on eight potato genotypes was compared to the susceptible cv. Desiree in four glasshouse experiments. The initial nematode densities consisted of log series 2x, with . Seinhorst’s logistic model was fitted to the final population densities to estimate the parameters maximum multiplication rate (a), maximum population density (M) and the ratios RSa, RSM and . Average RSa and RSM of the seven resistant genotypes were smaller than 0.29%. The ratios on six resistant genotypes and cv. Desiree were the same, 1.3, indicating independence of RS. One genotype stood out with , whereby RSa < RSM. Both RS and were unaffected by pot size or experimental conditions. Screening protocols at second-stage juveniles (g dry soil)−1 in 2 or 3 kg pots were evaluated for distinctiveness between the two genotype groups. Based on the results, an optimal protocol for a routine resistance test is proposed.

Yield loss of carrot (Daucus carota) cv. Nerac caused by Meloidogyne chitwoodi and population dynamics of this nematode were studied using a range of 13 nematode densities at three seed densities (2, 4, 18 seeds pot−1) in a climate-controlled glasshouse. Yield and quality data were fitted to Seinhorst’s yield models. Final population densities were fitted to the population dynamic models for sedentary and free-living nematodes. The tolerance limits for yield loss were 0.34, 0.62 and 0.50, while that of quality were 0.012, 0.142 and 0.813 second-stage juveniles (J2) (g dry soil)−1 at increasing seed densities, respectively. The minimum yield (m), increased with seed density: 0.25, 0.30 and 0.50; the minimum quality yield was 0.10, 0.08 and 0.15 J2 (g dry soil)−1 at increasing seed densities, respectively. Both maximum multiplication rates and maximum population densities increased with increasing seed density but were generally low. Carrot cv. Nerac can be considered a bad host for M. chitwoodi.