Greenhouse Pepper Crops Research Articles

How plant and insect host characteristics affect pepper weevil Anthonomus eugenii parasitism efficacy by the pteromalid Jaliscoa hunteri

The pepper weevil Anthonomus eugenii (Cano) (Coleoptera: Curculionidae) is an economically important pest of both field and greenhouse pepper crops, Capsicum annuum Linnaeus (Solanaceae) in North America. Among its natural enemies is the parasitoid wasp Jaliscoa (= Catolaccus) hunteri (Crawford) (Hymenoptera: Pteromalidae), whose potential control of A. eugenii appears promising but is currently unclear. We conducted controlled environment trials to quantify A. eugenii offspring emergence following exposure to J. hunteri, examining how parasitoid exposure period, weevil host life stage, pepper cultivar, fruit size and abscission status affect weevil-natural enemy dynamics. In pepper cultivar comparison trials, we identified a significant reduction in weevil offspring emergence from three different cultivars of ornamental peppers infested by A. eugenii, but no difference among them. In trials comparing wasp exposure period and weevil larval instar, pepper plants of one cultivar (Blaze) were exposed to A. eugenii adults, and subsequently to J. hunteri wasps for either three or seven days, when offspring weevils were either at the L1 or L3 instar. Offspring emergence was significantly reduced up to 62% when L3 but not L1 weevils were exposed to wasps for 7 days. Following this longer exposure period, significantly greater weevil suppression occurred in small (71.7%) versus large fruit (62.5%), with an additional 15.1% weevil suppression resulting from attached relative to abscised fruit. These results highlight the potential for J. hunteri as a biological control agent of A. eugenii on pepper crops, with particular value in commercial greenhouse production where wasp retention rates can be high.

Harnessing CRISPR/Cas9 for Enhanced Disease Resistance in Hot Peppers: A Comparative Study on CaMLO2-Gene-Editing Efficiency across Six Cultivars

The Capsicum annuum Mildew Locus O (CaMLO2) gene is vital for plant defense responses against fungal pathogens like powdery mildew, a significant threat to greenhouse pepper crops. Recent advancements in genome editing, particularly using clustered regularly interspaced short palindromic repeats (CRISPR)/Cas9, have unlocked unprecedented opportunities for modifying disease-resistant genes and improving crop characteristics. However, the application of CRISPR technology in pepper cultivars has been limited, and the regeneration process remains challenging. This study addresses these limitations by investigating the feasibility of using the validated CaMLO2 genetic scissors system in six commercial hot pepper cultivars. We assessed the gene-editing efficiency of the previously reported high-efficiency Cas9/CaMLO2single-guide RNA (sgRNA)1-ribonucleoprotein (RNP) and the low-efficiency Cas9/CaMLO2sgRNA2-RNP systems by extending their application from the bell pepper ‘Dempsey’ and the hot pepper ‘CM334’ to six commercial hot pepper cultivars. Across the six cultivars, CaMLO2sgRNA1 demonstrated an editing efficiency ranging from 6.3 to 17.7%, whereas CaMLO2sgRNA2 exhibited no editing efficiency, highlighting the superior efficacy of sgRNA1. These findings indicate the potential of utilizing the verified Cas9/CaMLO2sgRNA1-RNP system to achieve efficient gene editing at the CaMLO2 locus in different Capsicum annuum cultivars regardless of their cultivar genotypes. This study provides an efficacious genome-editing tool for developing improved pepper cultivars with CaMLO2-mediated enhanced disease resistance.

Irrigation of protected pepper crops according to growth stage using dynamic evapotranspiration estimates increases the water use efficiency

Current knowledge on crop irrigation in greenhouses is limited, and most irrigation measures are based on evapotranspiration (ET) estimated using external climatic conditions. Moreover, crop water requirement estimation by the Penman-Monteith (PM) model assumes complete coverage of the soil by the plants and usually does not account for partial cover, which changes during the growth of annual crops. The main goals of the present research were: (i) to develop and apply irrigation demand estimates for greenhouse pepper crops during their growth, based on internal meteorological conditions and real-time plant characteristics; and (ii) to examine the effect of that irrigation on yield. Experiments were conducted during two consecutive seasons in greenhouse pepper crops in the Jordan Valley region of eastern Israel. Four irrigation treatments were applied based on four different ET models: (i) PM model for outside reference evapotranspiration based on the FAO56 methodology, also denoted as the commercial treatment; (ii) PMrb model for pepper plants, which is a standard PM model in which a boundary layer resistance replaces the aerodynamic resistance; (iii) Shuttleworth-Wallace Layer (SWL) model which considers the soil and plants as separate interactive layers; (iv) Shuttleworth-Wallace Patch (SWP) model which considers the soil and plants as independent patches. The commercial treatment used external climatic conditions from a nearby meteorological station, whereas the other three treatments used internal meteorological conditions measured inside the greenhouse. Results showed a high correlation (R2 > 0.88) between leaf area index, vegetation cover fraction, and plant height during plant growth. Using the same meteorological conditions inside the greenhouse, the seasonal ET estimated by the PMrb model, which considers full vegetation cover, was larger by 21-28% than the SWL and SWP models, which consider the partial plant cover. Irrigation doses were deduced from ET multiplied by crop coefficients derived in a previous study for the same crop and structures. Using average data of the two seasons, we found that seasonal irrigation based on the two SW models was lower by 5-15% than that based on PMrb, and by 35-42% than the commercial irrigation. The water use efficiency of the commercial treatment was the lowest, while for the other treatments it was about 0.02 ton m-3 and higher by about 40% than the commercial. We conclude that irrigation of annual crops based on partitioning ET into evaporation and transpiration based on crop coverage and using internal climatic conditions allows water-savings without significant yield loss.

Botanical formulations for the ecological management of Myzus persicae (Sulzer) and Aphis gossypii (Clover) (Hemiptera: Aphididae) and their side effects on parasitoids

The peach aphid Myzus persicae (Sulzer) and cotton aphid Aphis gossypii (Clover) (Hemiptera: Aphididae) are considered to be key pests affecting greenhouse pepper crops in Argentina as a result of their frequent occurrence and the seriousness of the damage caused by their feeding behavior and the transmission of virus. The goal of this research was to determine the efficiency of botanical products to control aphids and their side effects on parasitoids in this crop. Thus, three biorational pest control formulations derived from essential oils (EO) and plant extracts (Es) were tested, namely (i) neem EO, cinnamon EO, clove EO, oregano EO and American marigold EO (formulation 1); (ii) garlic EO and cinnamon EO (formulation 2); (iii) garlic E and rue E (formulation 3); and a soy lecithin adjuvant (lecithin), and finally, a control (water spray method). For this research, a completely randomized design was replicated 3 times. These treatments were applied directly to the foliage by means of a backpack sprayer on a weekly basis until the end of this trial. Subsequently, the total number of healthy aphids and parasitized aphids (mummies) on every leaf was recorded in the field and the laboratory through repeated measures Analysis of Variance (ANOVA) and LSD Fisher method. The results showed that formulation 1 and formulation 3 recorded a lower number of aphids and mummies compared to the other treatments. This evidence would demonstrate that these formulations repel aphids and parasitoids without the lethal effects caused by the use of broad spectrum insecticides.

Analytical Economic Study of The Production of Cucumber and Pepper Crops In Greenhouses (A Case Study in Giza Governorate) دراسة اقتصادية تحليلية لإنتاج محصولي الخيار والفلفل بالصوب الزراعية (دراسة حالة بمحافظة الجيزة)

استهدف البحث الوقوف على مدي التفاوت بين المستوى الفعلي ونظيرة المرتقب لإنتاج الصوب من اهم محاصيل الخضر، وما مقدار انعکاس استخدام الزراعة المحمية علي کفاءة استخدام عناصر الانتاج المستخدمة في انتاج اهم محاصيل الخضر، هذا وقد تم الاعتماد على بعض طرق التحليل الإحصائي لتحقيق أهداف البحث، کأسلوبي الانحدار الخطي البسيط والمتعدد، هذا إلى جانب استخدام الصورة اللوغاريتمية المعروفة في التطبيقات الإحصائية بدالة کوب- دوجلاس، نموذج التعديل الجزئي، هذا وقد أمکن التوصل إلى عدة نتائج أهمها ما يلى: تبين تزايد معدلات التغير أو النمو السنوية لعدد الصوب ومساحتها المنزرعة بالخضر الشتوي، الأمر الذى أدى إلى تزايد معدلات النمو السنوية لإنتاجها خلال الفترة ( 2004-2018). أوضحت نتائج البحث توقع تزايد المستوى المرتقب لإنتاج الخضر بالعروة الشتوي بالصوب الزراعية خلال الفترة (2023-2027) من حوالى 260.87 ألف طن عام 2023 إلى نحو 283.53 ألف طن عام 7202 بمتوسط سنوى قدر بحوالى 272.20 ألف طن خلال الفترة المذکورة. کما أوضحت النتائج توقع تزايد المستوى المرتقب لإنتاج محصول الخيار خلال الفترة ((2023-2027) من حوالى 140.95 ألف طن عام 2023 إلى نحو 152.16 ألف طن عام 7202 بمتوسط يقدر بحوالى 146.56 ألف طن خلال الفترة المذکورة. کما أوضحت النتائج توقع تزايد المستوى المرتقب لإنتاج محصول الفلفل خلال الفترة ((2023-2027) من حوالى 92.585 ألف طن عام 2023 إلى نحو 107.35 ألف طن عام 7202 بمتوسط يقدر بحوالى 99.96 ألف طن خلال الفترة المذکورة هذا وقدرت ربحبة الجنية المنفق بحوالي 0.82، 0.61 جنيها لمحصولي الخيار والفلفل بالصوب الزراعي على الترتيب، بينما بالأراضي المکشوفة قدرت بحوالي 0.71، 0.44 جنيها کل على الترتيب.

Assessing New Tools for Management of the Pepper Weevil (Coleoptera: Curculionidae) in Greenhouse and Field Pepper Crops.

The pepper weevil, Anthonomus eugenii Cano, is an economically important pest of field and greenhouse pepper crops in North America. In this study, a series of insecticides covering a broad-spectrum of insecticidal modes of action were assessed for their potential in managing the pepper weevil under laboratory and greenhouse conditions. To accomplish this, laboratory mini-spray tower and greenhouse cage trials were conducted that evaluated the efficacy of 16 conventional, reduced-risk, and microbial insecticides. In laboratory trials, adult weevils were sprayed with insecticides, placed on treated leaves within a cup cage, and were monitored for their survival over 10 d. Of the 16 insecticides tested, 8 provided greater than 60% weevil control, a threshold considered necessary for including products in further greenhouse testing. In greenhouse trials, adult weevil mortality, bud and foliar damage, bud and fruit abortion, and subsequent weevil offspring emergence were measured following each of three weekly insecticide applications. The most efficacious insecticides included kaolin clay and mineral oil, which performed as well as the thiamethoxam-positive control, and incurred 70 and 55% of adult weevil mortality, respectively. Additionally, kaolin clay and mineral oil reduced offspring weevil emergence by 59 and 54%, respectively, compared with untreated controls. Despite the clear challenge that controlling this pest represents, this study has identified useful new tools for the integrated management of the pepper weevil, which may accelerate the rate at which these become available for use in greenhouse and field pepper production.

An Overview of the Pepper Weevil (Coleoptera: Curculionidae) as a Pest of Greenhouse Peppers

Abstract The pepper weevil (Anthonomus eugenii Cano) is a destructive insect pest of field and greenhouse pepper crops across North America. Its management remains challenging with significant implications for pepper production, despite a documented presence in Central America, Mexico, the United States, and the Caribbean for approximately a century, and recently in Canada. Currently, the main tools and methods applied to manage pepper weevil populations in greenhouse peppers are the implementation of strict biosecurity protocols, diligent monitoring, physical and cultural management techniques, and chemical insecticides when necessary. However, these tools can be costly, labor-intensive, and insufficient, particularly when new outbreaks go undetected for prolonged periods. Additionally, the use of available insecticides is limited due to significant nontarget effects these have on biological control agents used to manage other important greenhouse pepper pests. Recently, research efforts have focused on developing better tools for pepper weevil management to mitigate a rising incidence of insecticide resistance and the spread of weevils into temperate regions, however, multiple constraints remain. Here, we review the current state of knowledge of the pepper weevil and identify information gaps, which future research should address to improve the targeted management of this pest in greenhouse pepper production systems.

Combination of biosolarization and grafting to control Meloidogyne incognita in greenhouse pepper crops

The efficacy of combining biosolarization and grafting as integrated control of Meloidogyne incognita was evaluated in greenhouse pepper crops in south-east Spain. Field trials were conducted over a three consecutive year period in four greenhouses with soils naturally infested with M. incognita populations, virulent (two greenhouses) or avirulent (two greenhouses) to the Me3 gene. The soils were biosolarized (for 6 weeks from August) using fresh sheep manure as organic amendment. Susceptible varieties were grafted onto Atlante (heterozygous Me3) rootstock. The combined use of grafted plants + biosolarization was found to reduce the severity and incidence of the nematode disease more effectively than biosolarized soil only strategies, in greenhouses with populations virulent to Me3, as measured by the gall index (0.3 vs. 5.3 or 1.5 vs. 3.3) and the percentage of infected plants (16.6% vs. 96.6% or 43.3% vs. 71.1%). However, in cases of greenhouses containing populations avirulent to Me3 no differences were observed. In the greenhouses with populations virulent to Me3, marketable yield obtained from grafting + biosolarization treatment was 1.1 kg m−2 higher than that obtained from biosolarization treatment alone in four of the six trials. However no increase in production in greenhouses with populations avirulent to Me3 was observed. Grafting + biosolarization proved to be an effective and durable method for controlling M. incognita in greenhouse pepper crops. Moreover, biosolarization reduces the risk of the development of populations capable of overcoming resistance conferred by Me3 gene.

Eficacia de insecticidas botánicos sobre <i>Myzus persicae</i> (Sulzer) y <i>Aphis gossypii</i> (Clover) (Hemiptera: Aphidiae) en el cultivo de pimiento (<i>Capsicum annuum</i> L.) bajo cubierta

Una gran variedad de artrópodos plaga causan, a nivel mundial, perjuicios en cultivos hortícolas. Myzus persicae (Sulzer), Aphis gossypii (Glover) (Hemiptera: Aphididae) son las principales plagas de artrópodos que afectan a cultivos de pimiento bajo cubierta. El propósito de este estudio fue determinar la efectividad de cuatro productos botánicos diferentes como una alternativa ecológica para el control de pulgones en cultivo protegido de pimiento en Concordia, Argentina. Se probaron formulaciones de extractos/aceites vegetales a base de: aceite esencial de canela Cinnamomun verum (J. Presl.) [AE canela]; aceite esencial de cuasia Quassia amara (L.) [AE cuasia], aceite de neem Azadarichta indica (A. Juss.) [M neem] y extracto de ajo Allium sativum (L.) [M ajo]. Cabe aclarar que éstos dos últimos contienen a su vez otros extractos/aceites esenciales que fueron comparados con un testigo absoluto (agua). Se realizó una distribución de acuerdo con un diseño totalmente aleatorio con tres repeticiones. Los tratamientos se aplicaron directamente sobre el follaje con mochila manual iniciándose 1 semana después del trasplante y luego, semanalmente, hasta finalizar el ensayo. Posteriormente, se evaluó el número promedio total de pulgones por hoja. Estos resultados mostraron que el tratamiento con aceite de neem (en mezcla M neem) registró un número de pulgones menor comparado con el resto de los tratamientos y testigo absoluto. Sin embargo, el mayor número de pulgones parasitados (momias) fue observado en las hojas tratadas con el aceite esencial de cuasia (AE cuasia).

Assessment of the influence of working pressure and application rate on pesticide spray application with a hand-held spray gun on greenhouse pepper crops

Choosing the appropriate machinery for applying pesticides is crucial. Despite the availability of technologically more advanced equipment, the hand-held spray gun is still widely used today for spraying greenhouse crops because of its ease of operation and its low economic cost. Growers believe that a high spray application rate and a high pressure are needed to achieve good pest and disease control. In this study, the effects of pressure and volume application rate for application of treatments using a hand-held spray gun to greenhouse pepper crops were evaluated. In the first case, three different pressures were assessed: a reference at 2000 kPa (P20) and two others at 1500 kPa (P15) and 1000 kPa (P10). To test the effects of application volume, three application volumes were used: one considered to be reference (V100), applied by an experienced grower, and two reductions thereof, i.e. 25% (V75) and 50% (V50). Each test was made at two different stages of crop development. The results showed that the use of high pressures did not improve either the deposition or the penetration into the crop canopy and the losses to the ground were not significantly different. On the other hand, a reduction by some 25% of the application rate routinely used by local farmers caused major reductions in deposition on the plant canopy, which might possibly compromise pest and disease control. The losses to the ground diminished with the application rate, although differences were not significant between V100 and V75.

Survival reduction of Phytophthora capsici oospores and P. nicotianae chlamydospores with Brassica green manures combined with solarization

Phytophthora capsici and Phytophthora nicotianae are the main soil-borne pathogens of greenhouse sweet pepper in Southeast (Murcia) and P. nicotianae of open field paprika pepper crops in West (Extremadura) of Spain. Both oomycete cause plant root rot. The effects of green manure amendment (Brassica carinata, Brassica nigra, Sinapis alba, non-amended as control), transparent plastic tarp (non-tarped=biofumigation, tarped=biosolarization) and depth (15cm, 30cm) were assessed for the survival of P. capsici oospores and P. nicotianae chlamydospores in two consecutive years. In Murcia, biosolarization for six weeks significantly reduced the viability of oospores (values for the two soil depths ranged from 4.0–12.2% viables in biosolarized soil to 21.2–26.0% in non-treated soil in 2010 and from 6.9–31.1% to 52.4–54.9% in 2011) and the infectivity of oospores (values for the two soil depths and the two years ranged from 0.0–11.1% of diseased plants in biosolarized soil to 8.3–44.4% in non-treated soil) and chlamydospores (0.0% to 0.0–11.1%). The reduction of inoculum viability was greater with S. alba and B. nigra (6.6 and 5.7% of viable oospores) than with B. carinata (18.9%) and higher than in the non-treated soil (21.2%). Despite the low soil temperatures in Extremadura (15–29°C), S. alba further reduced chlamydospore infectivity when compared to B. nigra or non-amended soil in the second year (29.2, 52.1 and 45.9% of diseased plants respectively). Biosolarization with brassicas can be recognized as an effective method to reduce Phytophthora survival in soils of greenhouse pepper crops of Murcia and with better effects on infectivity of inoculum of P. nicotianae (0.0% diseased plants) than on P. capsici (0.0–11.1% diseased plants). Conversely, the results in Extremadura were not sufficiently consistent in the two year experiment thus, this procedure cannot be recommended for Phytophthora control in Extremadura open field.

Host suitability of peppers to the false root-knot nematode Nacobbus aberrans

The false root-knot nematode, Nacobbus aberrans, causes severe damage to field and greenhouse pepper crops in several localities of the American continent. No commercial peppers (Capsicum annuum) resistant to this nematode are available up to the present. Host suitability of 6 experimental and 3 commercial peppers (some of them carrying Me1 and Me7 resistance genes to Meloidogyne spp.) to two N. aberrans populations were evaluated under greenhouse experiments. None of the peppers was found to be resistant to the nematode. The evaluated parameters exhibited significant differences among some peppers tested within a single population and between populations for a single plant material. Some peppers carrying resistance showed higher nematode reproduction than some lines that did not possess resistance genes. These results confirmed that the genes conferring resistance to Meloidogyne spp. do not provide protection against this species of root-galling nematode. Host suitability of pepper lines carrying Me1 or Me7 resistance genes against N. aberrans is evaluated for the first time. Search for resistant genes against this nematode in wild peppers growing in areas where this nematode is indigenous should be promoted.

Development of virulence to Meloidogyne incognita on resistant pepper rootstocks

The root-knot nematode (RKN) Meloidogyne incognita is a major soil parasite of pepper crops in greenhouses in Southeast Spain. Due to the limitations of the use of soil fumigants, grafting plants on resistant rootstocks (R-rootstocks) has become an important alternative to chemical nematicides. The repeated use of R-rootstocks can bring about the selection of virulent populations capable of overcoming resistance. We carried out a six-year investigation on resistant rootstocks in a naturally M. incognita infested greenhouse, and found that two successive years of growing plants grafted on R-rootstocks Atlante (ATL) were sufficient to overcome resistance (galling index 1.5 and 5.6 in the first and second years respectively). A large variability was observed between several R-rootstocks. Two R-rootstocks (C19 and Snooker) behaved like ATL while two others (Terrano and DRO 8801) were not infected by RKN. Laboratory studies with the same R-rootstocks, inoculated with two nematode isolates (avirulent and virulent against ATL) confirmed the greenhouse results, indicating that some rootstocks may be infested by virulent populations and others may not. It suggests that different R-genes, which are differentially overcome by RKN, have been introgressed into the rootstocks. This may have consequences for the management of resistant rootstocks in the field.

Implications of phenotypic variation of Myzus persicae (Hemiptera: Aphididae) for biological control on greenhouse pepper plants

AbstractVariation in vulnerability to natural enemies, reproductive rate and insecticide resistance among phenotypes of Myzus persicae (Sulzer) has been shown to have the potential to disrupt biological control and IPM of this species, and movement of particularly troublesome phenotypes in international horticultural trade could be cause for concern. Three important components of fitness, vulnerability to parasitoids, reproduction and insecticide resistance were determined in three clones of M. persicae originating from prevalent phenotype populations on pepper crops in greenhouses in British Columbia, Canada. One of these phenotypes appeared to be consistently involved in outbreaks in commercial operations. These clones were also characterized for their DNA microsatellite genotype and compared with genotypes of M. persicae from Europe. The clone involved in outbreaks in commercial greenhouses showed reduced vulnerability to parasitoids, and a higher reproductive rate compared to the other two clones suggesting that these traits may have been involved in outbreaks. As in M. persicae European clones, a higher reproductive rate was correlated with a lack of esterase‐based resistance (primarily to organophosphates and, to some extent, to carbamates and pyrethroids). However, microsatellite analysis demonstrated that the three clones investigated in British Columbia had unique genotypes, and therefore there was no evidence for their movement in international trade.

Dermal Exposure of Pesticide Applicators as a Measure of Coverall Performance Under Field Conditions

In this study, the field performance of two coverall designs used by pesticide applicators was determined. Two coverall types were selected based on data from previously conducted comfort testing under field conditions in southern Europe. Dermal exposure was measured during 22 applications conducted with 11 operators using similar hand-held spray guns in greenhouse pepper crops in the Ierapetra region of Crete, Greece. One of the coverall designs studied was made from a cotton/polyester material treated with a water-repellent Resist Spills(R) finish, which was compared in the field study to a coverall of similar design, but using a woven, untreated cotton material. An in-house analytical method was developed and validated for determining residues of the active substance (a.s.) malathion on the dosimeters. The derived levels of dermal exposure were used as a measure of the protection provided by the two types of coveralls. In addition, by comparing the total amount of the a.s. recovered from outer and inner dosimeters (potential dermal exposure = 238.8 mg kg(-1) a.s. for the cotton coverall and 160.44 mg kg(-1) a.s. for the Resist Spills coverall), a value could be determined for the degree of coverall penetration. The mean penetration (milligrams per kilogram a.s.) of the outer coveralls, calculated as a percentage of the total contamination, was 0.4% for the water-repellent coverall and 2.3% for the cotton coverall. The mean recovery from the laboratory and field-fortified samples was >91 and 74%, respectively and used as the main criterion for quality control of the analytical data. Under the field trial conditions evaluated, both the coverall designs gave better protection than the default values used in the most relevant predictive exposure model. Therefore, they could be considered as appropriate tools of personal protection when both comfort and field performance is taken into account under the specific application scenario.

Insensitivity to Metalaxyl Among Isolates of Phytophthora capsici Causing Root and Crown Rot of Pepper in Southern Italy.

Pepper (Capsicum annuum L.) has become an economically important crop in the coastal provinces of Catanzaro and Vibo Valentia, in Calabria (southern Italy). An old local selection Riggitano, very susceptible to root and crown rot caused by Phytophthora capsici Leonian, is the prevalent cultivar in this area. Although repeated applications of metalaxyl are used as a soil drench, severe outbreaks occur each year on greenhouse crops. To examine metalaxyl resistance in P. capsici, 60 single-hypha isolates of P. capsici were tested in vitro for their level of sensitivity to metalaxyl. The isolates were collected from 1992 to 1997, during epidemic outbreaks of root and crown rot, from two commercial greenhouse pepper crops, near Vibo Valentia and Lametia Terme (Catanzaro). Fungicide sensitivity was determined by plating mycelial plugs onto potato dextrose agar (PDA) amended with metalaxyl. The fungicide was added to PDA after autoclaving, at final concentrations of 0.1, 1, 5, 10, 50, 100, and 200 μg/ml a.i. The percentage of inhibition of radial growth on metalaxyl-amended medium compared with the growth on unamended medium was determined after 6 days of incubation in the dark at 25°C. Three replicate petri dishes were used per treatment and each test was performed twice. The isolates were paired in culture on V8 agar with isolates of P. capsici of known mating type and all proved to be A2 mating type. Significant variation was observed among the isolates tested in responce to metalaxyl. The ED50 values for in vitro inhibition of mycelial growth by metalaxyl ranged from 1 to 11 μg/ml, whereas an ED 50 value of 0.1 μg/ml had been reported for a wild-type isolate of P. capsici obtained from pepper in northern Italy (3). The variation observed among the isolates from Calabria appeared unrelated to both the geographical origin and the year of isolation. The isolates from Calabria were inhibited by between 1 and 12% at 0.1 μg/ml and by between 7 and 27% at 1 μg/ml, proving to be less sensitive to metalaxyl than isolates from Capsicum spp. originating from Central America, tested by other authors (1). According to the criterion used in a recent screening for sensitivity to metalaxyl (2), 19% of the isolates from Calabria should be considered sensitive, as they were inhibited by more than 60% at 5 μg/ml, while all the others were intermediate, as they were inhibited less than 60% at 5 μg/ml but more than 60% at 100 μg/ml. On the basis of this preliminary screening, we report the presence of insensitivity to metalaxyl in field isolates of P. capsici in southern Italy. Although no isolate tested appeared highly resistant to metalaxyl, the presence of a high proportion of isolates with an intermediate level of resistance should be a reason for the growers to use metalaxyl more cautiously to control root and collar rot.