Net blotch in semi arid regions of Morocco. I Epidemiology

Net blotch caused by Pyrenophora teres F. teres, is one of the important diseases in Moroccan barley fields. Contributing factors include the lack of adequate disease and crop management. Furthermore when agricultural techniques were recommended without disease control, objectives were seldom reached and resulted in adverse growers’ reaction. To sustain farmers in the Moroccan semi-arid regions and to optimize barley production, we have focused on net blotch epidemiology and the development of adequate disease management approaches. A field experiment, conducted in five locations for two consecutive years, used six cultivars with different levels of susceptibility to net blotch. These cultivars were grown under high, medium and low inoculum levels of the pathogen, and with and without disease control. Hence, a broad range of disease epidemics was generated. All the disease progress curves showed a depression in disease severity at stem elongation. The boost in biomass production coupled with the relationship between initial disease severity and area under the disease progress curve led us to recommend seed treatment and/or seedling resistance as the initial means of disease control. Although statistical differences were measured in disease severity between fungicide treated and inoculated plots during the growing season, biological differences were not substantial until all the cultivars attained boot stage. Because of this, a single application of foliar fungicide is necessary at boot stage, with a second application needed toward the end of ear emergence when weather conditions favor disease development.     

Connection between primary Fusarium inoculum on gramineous weeds, crop residues and soil samples and the final population on wheat ears in Flanders, Belgium

Fusarium head blight (FHB) is a devastating wheat disease and is influenced by weather conditions and agronomic factors. Since FHB is a mostly monocyclic disease, the quantity of primary inoculum is a key factor influencing its incidence. To investigate the connection between the primary Fusarium inoculum and the final population on wheat ears, naturally occurring populations of Fusarium avenaceum, Fusarium culmorum, Fusarium graminearum, Fusarium poae and Microdochium nivale were studied at eight locations in Flanders, Belgium during the growing seasons of 2008-2009 and 2009-2010. To determine the composition of the primary inoculums in November, weeds, wheat and maize residues as well as soil samples were examined. At the end of the growing season, in July, the population on wheat ears was determined. In both growing seasons, the population was characterized by a large complexity and a differential composition at each location and for each type of sample. Nevertheless, some clear correspondences were observed: F. culmorum was a predominant species in crop residues and in soil samples in November, while the population on wheat ears in July consisted mainly of F. graminearum and F. poae, with only a lower frequency of F. culmorum, indicating that soil is not an important source of primary inoculum. The presence of M. nivale was restricted to weeds, crop residues and soil samples in November, and was nearly absent in July at the majority of locations. Finally, our results also indicate that the Fusarium population in July is more complex than the population at the beginning of the season in November. The information of the primary inoculum and the composition of the FHB population at the end of the growing season is important to predict FHB incidence and to implement control strategies for FHB.     

Dynamics of reproductive growth of lesquerella (Physaria fendleri) over different planting dates

Vegetative and reproductive growth information of lesquerella (Physaria fendleri), a new oilseed crop targeted for bio-products, is important to understand especially in the early commercialization stage of this new crop. The objective of this study was to determine the effect of fall, winter, and spring planting dates over three years on the ontogeny of the crop including biomass, floral buds, flowers, and siliques. Fall plantings always produced more than the other plantings due to the extended season. Winter and spring plantings had less biomass and produced fewer buds, flowers, and siliques. The compensation of lower crop management costs and a shorter growing season could make winter a viable option for planting in the southwest. Spring planting could become viable if seed shatter due to summer rains could be reduced. The information will help decide growing regions suitable for crop production and determine what reproductive stages could be manipulated to improve seed yields.     

Population dynamics of Verticillium species in cauliflower fields: Influence of crop rotation,debris removal and ryegrass incorporation

Verticillium wilt, caused by the soil-borne fungus Verticillium longisporum, leads to economic losses in cauliflower production in Belgium. Development of sustainable control measures of the disease is necessary. Previous studies in our laboratory have shown that incorporation of ryegrass can reduce the viability of V. longisporum microsclerotia in soil. However, field experiments are lacking in Belgian conditions. To gain knowledge about the population dynamics of V. longisporum and its relationship with Verticillium wilt, experiments were conducted from 2006 to 2010 in two cauliflower fields (Oppuurs and Ardooie) with history of Verticillium wilt. Three main crop systems (fallow, cauliflower and cauliflower followed by removal of debris) and two cover crop systems (no cover crop and ryegrass) were tested. The results of this study showed that (i) crop rotation intensity of cauliflower cultivation does not affect the inoculum density of microsclerotia forming Verticillium species in soil, (ii) amendment of lignin-rich ryegrass may reduce the soil inoculum, and (iii) seasonal fluctuations of inoculum densities occur but any soil inoculum variation above a level of one microsclerotium per gram of soil does not affect disease levels. Furthermore, we found that Verticillium wilt of cauliflower in Ardooie was reduced in soil containing Verticillium tricorpus-like organisms. The Verticillium isolate Vt305 obtained from the cauliflower field in Ardooie was morphologically similar to V. tricorpus, but its rDNA ITS region showed 100% identity with the non-pathogenic species Verticillium isaacii, recently described in literature.     

Potentials and Limitations of Existing Forecasting Models for <Emphasis Type="Italic">Alternaria</Emphasis> on Potatoes: Challenges for Model Improvement

Alternaria species, including A. solani and A. alternata, are a serious threat to potato cultivation and cause necrotic leaf spots, leading to premature defoliation and yield losses. To reduce the impact of the disease, a timely prediction of a disease outbreak is important. Worldwide, modelling attempts have been made to predict the occurrence of Alternaria in order to take adequate measures. In the present paper, we made an effort to classify the existing prediction models and subdivided them into three categories: plant-based, pathogen-based and plant-pathogen-based models. Plant-based models predict the susceptibility of the host crop and presume that Alternaria inoculum is abundantly present and not the restrictive factor, whereas pathogen-based models consider one or more stages of the Alternaria life cycle and suppose that the host crop is always susceptible. The plant-pathogen-based models try to take into account the complete plant-pathogen-environment relationship. In this paper, a critical review of the described models for Alternaria leaf spot is presented. To illustrate the discrepancy between the predicted and the observed dates of the first Alternaria symptoms or the discrepancy between the suggested first treatment and necessity to treat Alternaria, the existing models were subjected to the Belgian weather conditions. It turns out that these models are not applicable in Belgium or similar regions. This can be partially attributed to the fact that most of the currently available models are too simplistic (only plant- or pathogen-based) for regions where the disease pressure highly fluctuates between growing seasons and between locations within one season. Finally, perspectives for model improvement are given taking into account both plant, pathogen and environment.     

Influence of maize–wheat rotation systems on Fusarium head blight infection and deoxynivalenol content in wheat under low versus high disease pressure

Fusarium head blight (FHB) is one of the most destructive fungal diseases of small grain cereals resulting in a reduced grain yield and quality. FHB is the result of a complex interaction between weather conditions and agricultural practices including crop rotation, tillage, fungicide application and host resistance. This study deals with the results of field experiments conducted during the growing seasons 2009–2010 until 2011–2012 at Bottelare (Belgium). The experiments were set up to evaluate the influence of maize–wheat rotation on the visual symptoms of FHB and deoxynivalenol (DON) content in winter wheat. Using a randomised complete block design with four replications, we studied the impact of (a) maize variety as previous crop, (b) maize harvest method (grain or silage maize), (c) tillage method and (d) the influence of the wheat variety resistance on the FHB incidence and DON content. The experimental results showed that the susceptibility of the maize varieties for Fusarium and maize harvest method had only a minor effect on the FHB incidence and DON content of the wheat crop during the subsequent growing season. The tillage method and wheat variety resistance were more important; both factors had a significant influence on the FHB incidence and DON content. Furthermore, the quantitative effect of these factors depended on the disease pressure. The DON content reduction obtained by ploughing and by sowing moderately resistant wheat varieties was higher in case the weather conditions favoured FHB development. Furthermore, it was shown that repeated maize–wheat rotation in combination with favourable weather conditions for FHB could result in an accumulation of inoculum, which, for instance, led to DON contents up to 9.90 mg/kg in August 2012.     

Biocontrol of vascular wilt and corm rot of gladiolus caused by Fusarium oxysporum f. sp. gladioli using plant growth promoting rhizobacterial mixture

Talc-based formulations of plant growth promoting rhizobacterial strain S2BC-2 (Bacillus atrophaeus) and strain mixture, S2BC-2 + TEPF-Sungal (Burkholderia cepacia), inhibitory to the growth of Fusarium oxysporum f. sp. gladioli (FOG), were developed for corm dressing and soil application in gladiolus. In comparison to the individual strain, the strain mixture recorded maximum spike and corm production of 100 and 150%, respectively with less vascular wilt and corm rot incidences of 73.6 and 54.8% reduction over the pathogen control in greenhouse when inoculated with FOG. Reduction in disease incidence under greenhouse conditions occurred through induction of defence gene products such as chitinase, β-1,3-glucanase, peroxidase and polyphenol oxidase. Besides disease suppression, treatment with strain mixture promoted plant growth in terms of enhanced corm and cormel production and flowering. In field experiments, the strain mixture recorded less vascular wilt and corm rot incidences of 48.6 and 46.1% mean reduction over the non-bacterised control, and was almost comparable with that of fungicide (51.5 and 47.1%, respectively). The treatment also recorded increased spike and corm yield with average increases of 58.3 and 27.4%, respectively, relative to the control.     

Control of grassy weeds in annual canarygrass

There are currently no herbicides registered in Argentina for the selective control of grassy weeds in annual canarygrass (Phalaris canariensis L.). The principal grassy weeds are darnel ryegrass (Lolium temulentum L.) and wild oats (Avena fatua L.), which cause grain yield and quality losses. The potential of diclofop-methyl and clordinafop-propargyl for their control was assessed through greenhouse and field trials, in which crop phytotoxicity and weed control efficacy were evaluated. It was found that (i) field application of clordinafop-propargyl resulted in severe crop damage, except for low doses that did not affect the species to be controlled; (ii) although field application of diclofop-methyl resulted in a certain degree of phytotoxicity on wild oats, these effects were insufficient for efficacious control; and (iii) field and greenhouse application of diclofop-methyl between 200 and 500 g a.i. ha⁻¹ revealed differences between crop sensitivity and that of darnel ryegrass. In this range, crop phytotoxicity in the greenhouse was less than 20% compared to more than 60% in the weed, and in the field only slight crop phytotoxicity symptoms were observed. As in the greenhouse, field application resulted in significant phytotoxic effects upon darnel ryegrass, high efficacy levels, a low survival rate amongst treated plants and a notable reduction in seed production by surviving plants. Only the highest dose (500 g a.i. ha⁻¹) in one of the field trials resulted in a significant reduction in crop grain yield. Hence diclofop-methyl application appears to offer a promising means for controlling darnel ryegrass.     

Fungicide and cultivar effects on the development and temporal progress of wheat blast under field conditions

The epidemiology of wheat blast, caused by the Triticum pathotype of Pyricularia oryzae, is poorly understood, making it very difficult to manage. We reported on the individual and combined effect of host resistance and fungicide application for managing wheat blast disease on spikes. Two field experiments (Exp. 1 and Exp. 2) were conducted in a region of Brazil where blast is not known to be endemic to evaluate its development as influenced by fungicide and host resistance. Plots of wheat cultivars BR-18 (partially resistant) and Guamirim (susceptible) were either treated with the fungicide epoxiconazole + pyraclostrobin or left non-treated, and then inoculated with a spore suspension of P. oryzae at mid-anthesis. Spike blast incidence and severity, quantified at regular intervals after inoculation, increased over time, and fungicide and cultivar had statistically significant effects (P < 0.005) on both measures of disease and their temporal rates of progress. Relative to Guamirim-non-treated, BR-18-non-treated (resistance alone) led to 44 and 64% control of final incidence and severity, respectively, in Exp. 1, and 3 and 49% control, respectively, in Exp. 2. Guamirim-treated (fungicide alone) led to 65% control of incidence and 77% control of severity in Exp. 1, and 64% control of incidence and 95% control of severity in Exp. 2. For both incidence and severity, fungicide and resistance alone also reduced the temporal rate of progress relative to the susceptible non-treated. However, the greatest overall efficacy was observed when resistance and fungicide were combined, with over 70 and 90% control of final incidence and severity, respectively, and over 75% reduction in the temporal rate of spike blast progress. Based on percent control, the integrated effect of resistance and fungicide was additive for incidence, severity, and their temporal rates of progress, demonstrating the value of combining the two strategies to manage spike blast.     

Integration of environmental and fungicidal control of Bremia lactucae in a glasshouse lettuce crop

The effect of combinations of night ventilation regimes and fungicide treatments on levels of downy mildew (Bremia lactucae) was investigated in a November-sown glasshouse lettuce crop. Environmental regimes were allocated in a randomized-block design to glasshouse compartments in which fungicide treatments were applied to sub-plots from which sub-sub-plots were harvested on each of four dates. The benefit of night ventilation was strikingly shown. It was almost as effective as the systemic fungicide metalaxyl which gave complete control of B. lactucae for 20 weeks after its incorporation in the peat blocks. A ‘heat-purging’ treatment increased the incidence of downy mildew, while other fungicidal regimes failed to control late infection. In the period close to cutting, when fungicide usage is not permitted, night ventilation may be the only effective means of controlling the disease.     

Effects of Bacillus subtilis strain QST 713 and storage temperatures on post-harvest disease development on greenhouse tomatoes

Tomato plants in two commercial greenhouses were treated with Rhapsody (Bacillus subtilis strain QST 713, rate of 1.45%) once every 4 weeks during 2012–2013 to determine effects on post-harvest fruit infection. Populations of Bacillus and disease incidence were monitored weekly from harvested fruit over an 18-week period. Population levels of Bacillus ranged from 75 to 110 × 10⁴ colony forming units (cfu) cm⁻² of fruit surface area one week after application to 25–30 × 10⁴ cfu cm⁻² of fruit surface area 4 weeks after application. Disease incidence on harvested fruit incubated at 21 °C for 7–10 days was variable, due to variation in inoculum levels within the greenhouse as well as variable environmental conditions. Both disease incidence and severity were significantly reduced on Rhapsody-treated fruit, especially in the 1–2 week period following application. Post-harvest storage temperature (13 °C vs. 21 °C) and incubation time (12 vs. 16 days) had a significant effect on final disease severity. Rhapsody-treated fruit incubated at 13 °C had an average of 1–2% fruit infection compared to up to 20% infection on untreated fruit at 21 °C. The most frequent pathogens affecting fruit quality were Penicillium sp. and Rhizopus stolonifer. Rhapsody applications made every 4 weeks maintained sufficiently high populations of Bacillus on the fruit surface to prevent spread of these fungi onto the fruit, resulting in significant post-harvest disease control on fresh market tomatoes. When combined with storage at 13 °C for no more than 12 days, disease was reduced to negligible levels.     

Sensitivity of Fusarium verticillioides isolates from rice to a novel cyanoacrylate fungicide

The baseline sensitivity of Fusarium verticillioides to the novel cyanoacrylate fungicide 2-cyano-3-amino-3-phenylancryic acetate (experimental code JS399-19) was established, and its impact on the germination of rice seeds and efficacy in controlling rice bakanae disease by seed treatment were evaluated. The EC₅₀ values for JS399-19 inhibiting mycelial growth of wild-type F. verticillioides isolates ranged from 0.162 to 0.559 μg/ml (a 3.5-fold difference between the lowest and highest value), and the average (±SE) EC₅₀ value was 0.316 ± 0.072 μg/ml. The sensitivity curve was unimodal over the sensitive range and the sensitivity data can be used as a baseline for monitoring any future changes in sensitivity to JS399-19 by F. verticillioides populations. Germination of healthy seeds was greater than 77% for all the selected cultivars, and was unaffected by treatment with JS399-19. Treatment of infected seeds (harvested from diseased plants) with all concentrations of JS399-19 in this study significantly decreased the abnormal elongation and damping-off of seedlings in plastic bottles in the greenhouse, indicating that JS399-19 has excellent efficacy in controlling rice bakanae disease, and was safe to rice seeds. It could be used as a disinfectant of rice seeds infected by F. verticillioides. The results also suggested that the F. verticillioides isolates exhibited little sensitivity shift to this fungicide after a single application. If properly applied, JS399-19 might be used as a major fungicide or a good companion fungicide for the control of rice bakanae disease in China.     

Sources and seasonal dynamics of Alternaria inoculum associated with leaf blotch and fruit spot of apples

Alternaria leaf blotch and fruit spot caused by Alternaria spp. cause annual losses to the Australian apple industry. Control options are limited, mainly due to a lack of understanding of the disease cycle. Therefore, this study aimed to determine potential sources of Alternaria spp. inoculum in the orchard and examine their relative contribution throughout the production season. Leaf residue from the orchard floor, canopy leaves, twigs and buds were collected monthly from three apple orchards for two years and examined for the number of spores on their surface. In addition, the effects of climatic factors on spore production dynamics in each plant part were examined. Although all four plant parts tested contributed to the Alternaria inoculum in the orchard, significant higher numbers of spores were obtained from leaf residue than the other plant parts supporting the hypothesis that overwintering of Alternaria spp. occurred mainly in leaf residue and minimally on twigs and buds. The most significant period of spore production on leaf residue occurred from dormancy until bloom and on canopy leaves and twigs during the fruit growth stage. Temperature was the single most significant factor influencing the amount of Alternaria inoculum and rainfall and relative humidity showed strong associations with temperature influencing the spore production dynamics in Australian orchards. The practical implications of this study include the eradication of leaf residue from the orchard floor and sanitation of the canopy after harvest to remove residual spores from the trees.     

Integrated effect of Glomus mosseae and selected plant oils on the control of bacterial wilt disease of tomato

This study investigated the efficacy of Glomus mosseae and thyme and peppermint oils in controlling bacterial wilt disease (BW) of tomato caused by Ralstonia solanacearum under in vitro conditions and under greenhouse and field conditions. In an in vitro study, we tested nine plant oils against R. solanacearum, and the results demonstrate that only caraway, thyme, peppermint and marjoram oils inhibited the growth of the BW pathogen with differing degrees, thyme oil caused the highest reduction of the growth of the pathogen followed by peppermint and the lowest was caraway and marjoram. We evaluated the effect of thyme and peppermint under greenhouse and field conditions. Under greenhouse conditions, the thyme treatment exhibited the highest disease reduction percentage followed by the thyme + peppermint treatment, while G. mosseae caused the least disease reduction percentage. Under field experiments, thyme oil treatment exhibited the highest ability to reduce the disease by 94.8 and 97.1% in the 2011 and 2012 growing seasons, respectively, followed by the treatment of thyme oil + peppermint oil with the reduction of 89.5 and 82.4%, respectively. G. mosseae exhibited the lowest percentage of disease reduction; however, it caused a greater yield increase percentage during both of the tested seasons.     

Chemical control of root rot complex and stem rot of greenhouse cucumber in straw-bale culture

Experiments were conducted in three different commercial greenhouses wherein cucumber (Cucumis sativus L.) cv. Kalunga F₁ (Long English type) were grown in composted straw bales, heavily infested with Fusarium oxysporum Schlechtend.:Fr. f.sp. radicis-cucumerinum Vakalounakis (FORC), the causal agent of Fusarium root and stem rot of cucumber. FORC was isolated from roots and stem bases of symptomatic plants either in single infections or simultaneously with other root infecting pathogens, including species of Phytophthora and Pythium and Rhizoctonia solani Kühn AG-4. Verticillium dahliae Kleb. was obtained from individual cucumber plants showing wilt symptoms. Fungicide applications started at the beginning of fruiting time when the first symptomatic plants occurred and followed at 45-day intervals. Three fungicides, either alone or as tank-mixed combinations of 0.1% Topsin M 70WP (thiophanate-methyl 700 g kg⁻¹) plus 0.15% Previcur 607SL (607 g L⁻¹ propamocarb hydrochloride), or 0.1% Benomyl 50WP (benomyl 50 g kg⁻¹) plus 0.15% Previcur 607SL, were applied to the crown and root area of cucumber plants through drip irrigation systems as drenches at a rate of 0.25 L/plant. Plant mortality was reduced by 11.1%–84.8% and 23.8%–77.7% when plants were drenched with Topsin M 70WP in combination with Previcur 607SL or Benomyl 50WP plus Previcur 607SL, respectively. In comparison, significantly lower levels of disease control were achieved when these fungicides were applied individually. Three fungicide applications during the crop season increased the inhibitory effect of the fungicide regime on the disease incidence compared to one or two treatment.     

Enhancement of biocontrol efficacy of Pichia membranaefaciens by hot water treatment in postharvest diseases of citrus fruit

Effects of hot water treatment (HWT; 53 °C for 2 min) and Pichia membranaefaciens, either alone or in combination, on controlling Penicillium italicum, Penicillium digitatum, and natural infection in citrus fruit were investigated. Results showed that the combined treatment significantly reduced disease incidence and lesion diameters of blue and green molds in artificially inoculated fruit whether the pathogens were inoculated after or before the treatment compared with the treatment of P. membranaefaciens or HWT alone. The combination of P. membranaefaciens with HWT was as effective as the fungicide treatment in natural infection trials. Application of HWT did not affect the growth of P. membranaefaciens in the wounds of citrus fruit at 20 °C or 4 °C. P. membranaefaciens combined with HWT effectively enhanced the phenylalanine ammonia-lyase, peroxidase, polyphenoloxidase, chitinase, and β-1,3-glucanase activities and stimulated the synthesis of phenolic compounds. These results suggest that the use of HWT is a useful approach to improve the efficacy of P. membranaefaciens in postharvest diseases of citrus fruit.     

Reduced efficacy of rovral and botran to control Sclerotinia minor in lettuce production in the Salinas Valley may be related to accelerated fungicide degradation in soil

Accelerated soil degradation with repeated application was suggested to be responsible for the lack of efficacy of commercial fungicides to control lettuce drop caused by Sclerotinia minor in the Salinas Valley in California. In 2000, a study was initiated in a field artificially infested with S. minor to evaluate the efficacy and degradation potential of four selected fungicides (i.e., Rovral, Botran, Switch, and Endura). Crisphead lettuce was direct-seeded twice a year (spring and fall season) from 2000 to 2002. Fungicides were applied at recommended label rates twice during each season. Disease incidence was evaluated in fungicide treatments and nontreated control plots weekly starting immediately after thinning until harvest, and areas under the disease progress curves (AUDPC) were compared between treatments from 2000 to 2002. Soil samples (0–15 cm) were collected at regular intervals during the spring and fall 2002 lettuce seasons, and analyzed for residual fungicide concentration. Disease progress and final disease incidence were significantly affected by the fungicide treatment, season, year and interactions among these factors (p < 0.05). At the end of the three year experiment, up to 18 and 50% of the lettuce was infected by S. minor for the spring and fall seasons, respectively. Fungicide efficacy to control lettuce drop was highest for Endura, followed by Switch and Botran, and lowest for Rovral. Relative persistence in soils was lowest for Rovral and Botran, followed by Switch and Endura. In 2002, residual soil fungicide concentrations were 11% for Rovral and Switch, 23% for Botran, and 88% for Endura relative to their initial concentrations. Results of this study provide first evidence suggesting that reduced efficacy of lettuce drop control from Rovral and Botran in the Salinas Valley may be related to an accelerated degradation of these fungicides due to repeated application. However, insufficient fungicide persistence due to inherent properties of this sandy loam soil or the chemical structure of these fungicides can not be excluded. Both hypotheses deserve further investigation.     

Fusarium mangiferae侵染对凯特杧内源激素含量的影响

为探讨杧果感染畸形病过程中顶芽内源激素含量的变化规律,以凯特杧为试验材料,测定了接种病菌（Fusarium mangiferae）后顶芽内生长素（IAA）、赤霉素（GA3）和脱落酸（ABA）含量的变化情况。结果表明：接种病菌后,杧果顶芽内赤霉素和生长素含量急速上升,且在整个试验阶段明显高于健康处理,脱落酸含量在试验后期不断升高;分析发现,F. mangiferae侵染能够显著影响杧果顶芽内源激素的含量,改变IAA/ABA和GA3/ABA的平衡,致使杧果的生长发育受到影响,进而引发畸形病的产生。     

Management of peanut pod rot I: Disease dynamics and sampling

Peanut fields are monitored for pod rot, which is typically caused by Pythium spp. and Rhizoctonia solani, in order to determine need, and the type and timing of fungicide applications. Pod rot can lead to damaged peanut kernels and when damage exceeds 2.49%, substantial price reductions occur. Nine fields or tests were sampled weekly for pod rot during the 2009 through 2012 growing seasons. The sampling was conducted on fields treated uniformly with fungicides for pod rot or within large research plots with various fungicide treatments. Pythium myriotylum was the most frequently identified pathogen species, although Rhizoctonia spp. were also recovered from diseased pods at all sites. Pod rot incidence was related to percent damaged kernels at harvest in 3 of 5 sites. Collection of 304 samples (sample unit = 46 cm of row) in a field was required to estimate 1% pod rot accurately (CV = 20%). There was a linear relationship between average % pod rot in a field, and the percentage of sampling units (absence/presence) with pod rot at low disease incidences. Scouting for pod rot of peanuts to make in-season fungicide applications will be hampered by high sample number, destructive sampling of plants, frequent sampling (due to rapid increase of disease), and the poor relationship between disease during the season and kernel damage at harvest. Making one preventative application at 60–70 days after planting may be a better practice than timing the initial fungicide application based on sampling for disease.