José R. Liberato

Progresso de doenças fúngicas e correlação com variáveis climáticas em mamoeiro

The effect of climatic conditions on progress of fungal diseases of papaya were evaluated in three experimental areas in Linhares, State of Espirito Santo, Brazil. First area was carried out using traditional system and was drip irrigated; second area was also carried out using traditional system, but it was overhead irrigated, and third area was carried out using organic system with micro spray. It was evaluated three different systems of cultural control in the first area: 1- papaya plants not sprayed with fungicides with any leaf removal (check treatment without sanitation); 2- papaya plants not sprayed with fungicides with leaf removal (check treatment with leaf removal), and 3- papaya plants sprayed with fungicides without leaf removal (grower treatment). Each system received four plots with 20 plants. Evaluation was done in 10 plants in the center of plots. Incidence and severity of Ascochyta leaf spot, black spot and powdery mildew were evaluated on leaves. It was evaluated the incidence and stem end rot of fruits. Epidemics of Ascochyta leaf spot are favoured by temperatures ranging from 15 oC to 20 oC. Epidemic of black spot occurred when temperature ranged from 25 oC to 30 oC with relative humidity ranging from 80 to 100%, from november to march. Powdery mildew development was favored by temperatures from 15 oC to 20 oC and relative humidity from 60 % to 70%. It was not observed any relation between incidence of stem end rot of papaya and acumulated rain 15 days before the evaluation (r less than 0.21). Incidence of fruit rot diseases caused by anthracnose and chocolate spot did not correlate with weather conditions. Ascochyta leaf spot was detected in all the evaluation data with maximum severity from the juliana date 155 to 250 and minimum from 20 to 80; the black spot increased from date juliana 326 to 70 with maximum disease severity on the date 336; powdery mildew increased in two distinct times: one from the date 330 to 80 and another form the date 240 to 320 with maximum severity on the date from 240 to 250. Fruit rot was detected in stored papaya when they were harvested on the dates from 140 to 320. The pattern treatment employed by the growers differed significantly from the treatments involving cultural practices such as sanitization and no sanitization, with the exception for stem end rot, where the grower pattern treatment did not differ from the treatment with sanitization. The cultural treatments with sanitization did not differ from the treatment without sanitization. However for stem end rot, treatment with sanitization increased 24 % and 9 % the number of commercial fruits for the juliana dates 170 and 210, respectively over the treatment without sanitization; for anthracnose, 13 % and 55 %, for the juliana dates 160 and 230, respectively and for the chocolate fruit spot 30 % and 9 %, for the juliana dates 170 e 210, respectively. Total diseased progess curves in the areas called curral and Bitchisner were almost identical; the maximum severity of Ascochyta leaf spot was 20 % in the curral and 10 % in Bitchisner, from the dates 110 e 320. Black spot was more severe in the curral than in Bitchisner. Powdery mildew was detected on the plants from curral and Bitchisner from dates 230 aos 320 with higher severity on the plants of curral where the plants are irrigated with central pivot. Maximum disease severity of 45 and 65 % were detected on papaya areas from curral and Bitchisner, respectively. The incidence of papaya black spot was higher on the curral area than on the plants form Bitchisner due to the method of irrigation.

Streptopodium caricae sp. nov., with a discussion of powdery mildews on papaya, and emended descriptions of the genus Streptopodium and Oidium caricae

A new powdery mildew infecting papaya (Carica papaya) in Brazil, Streptopodium caricae sp. nov., is described. The species is compared with other anamorphic Erysiphales known to infect papaya: Oidiopsis sicula, Ovulariopsis papayae, Oidium caricae, O. papayae, O. caricicola, O. indicum, O. caricae-papayae, Podosphaera (syn. Sphaerotheca) spp., and Erysiphe spp. An emended description Streptopodium and a key to the anamorphs of powdery mildews on papaya are also presented. A re-examination of the type material of Phyllactinia caricaefolia showed that conidia in this material are dimorphic, indicating that its anamorph does not belong to Ovulariopsis and that the teleomorph is not conspecific with Phyllactinia guttata. Oidium caricae, the common powdery mildew of papaya, was re-examined, recognized as a member of subgenus Pseudoidium, an emended description was prepared, and a new type was indicated. O. papayae was recognized as a synonym of O. caricae, and many of the records of this fungus are considered to be doubtful or incorrect, either omitting a description of the fungus or including a description or illustration of an euodium conidiophore morphology.

Minimum number of assessment times to compare chemical control treatments for papaya fruit anthracnose

The chemical treatment evaluation in the field to control post-harvest fruit anthracnose (Colletotrichum gloeosporioides) requires a suitable disease incidence assessment on harvested papaya (Carica papaya) fruits. The minimum number of papaya fruit harvests was determined for valid treatment comparison in field trials for anthracnose chemical control. Repeatability analysis was done using previously published data. The coefficient determination (R2) estimate range, using four methods, and based on means of 12 assessment times, was 92.58 < R2 < 94.45%. The number of assessment times required for R2=90% varied from seven to nine. The R2 values of 85.1 < R2 < 91.3% estimated by ANOVA suggested that any seven successive assessment times were sufficient for treatment comparison.

Powdery mildew of Ruta graveolens in Brazil caused by Oidiopsis haplophylli

Oidiopsis haplophylli is described causing powdery mildew on Ruta graveolens for the first time in Brazil (Vicosa, MG). The fungus causes yellowing of infected leaves accompanied by the presence of a whitish mycelial colony abaxially. The following combination of characters typical of this species was observed on the specimens collected in Vicosa: mycelium hypophyllous, hemiendophytic (partly external and partly internal), entering the leaves through the stomata; conidiophores hypophyllous, produced from the internal mycelium emerging through the stomata, cylindrical, hyaline, smooth; conidia, isolate, dimorphic - primary conidia lanceolate, 66.5-91.5 x 11.0-20.0 mm l/w ratio 3.5-6.2, secondary conidia cylindrical with rounded ends, 57.0-81.5 x 13.5-20.0 mm, l/w ratio 3.1 - 5.3, aseptate, hyaline, smooth.