Cleide Maria Ferreira Pinto

Chemigation with benomyl and fluazinam and their fungicidal effects in soil for white mold control on dry beans

The effectiveness of fungicides in controlling white mold (Sclerotinia sclerotiorum) of dry beans (Phaseolus vulgaris) was evaluated when they were applied through irrigation water directly onto the plants or only to the soil. Two field trials were installed in April 1998 and April 1999 in Vicosa, MG. Trials were conducted as a (2 x 3) + 1 factorial: two fungicides x three application modes + one untreated control. The fungicides were benomyl (1.0 kg a.i. ha-1) and fluazinam (0.5 l a.i. ha-1). The three application modes were: (a) by backpack sprayer (667 l ha-1), (b) by garden watering-cans simulating sprinkler irrigation with 35,000 l ha-1 of water, and (c) by garden watering-cans applying water between the rows and near the soil surface in 35,000 l ha-1 of water. In 1998, fungicides were applied at 43 and 54 days after emergence (DAE); in 1999, at 47 and 61 DAE. Both fungicides were similarly effective on white mold control when applied by either chemigation or backpack sprayer, resulting in yields 21% higher than untreated control. Only fluazinam provided disease control when applications were made only in soil. Chemigation provided white mold control equivalent to that of backpack sprayer in terms of incidence, severity and number of diseased pods. Consequently, yield differences between these application methods were not significant.

Idade de colheita do feijão-vagem anão cultivar Novirex.

Foram conduzidos tres ensaios, dois em Vicosa e um em Coimbra, municipios da Zona da Mata de Minas Gerais, com o objetivo de se determinar a melhor idade de colheita do feijao-vagem cv. Novirex, de habito de crescimento determinado (tipo I). Em Vicosa, os ensaios foram instalados em 16/04/97 e 12/08/97 e em Coimbra, em 19/03/98. Irrigacao e controle de insetos foram feitos quando necessarios. Foi utilizado o espacamento entre fileiras de 0,5 m, com aproximadamente 15 sementes por metro. Foram avaliadas cinco idades de colheita, em intervalos de dois a quatro dias. A primeira colheita foi realizada antes do final da floracao, quando havia muitas vagens comerciais por planta e nenhuma vagem fibrosa. Em Vicosa (semeadura em 16/04/97), os maiores rendimentos de vagens comerciais (entre 8,6 e 10,1 t/ha) foram alcancados entre 63 e 71 dias apos a emergencia (DAE). No outro ensaio de Vicosa (semeadura em 12/08/98), os maiores rendimentos foram obtidos aos 56 e 60 DAE (7,4 e 7,7 t/ha, respectivamente). Em Coimbra, as colheitas realizadas aos 46 e 49 DAE proporcionaram os rendimentos mais altos (8,1 e 8,4 t/ha, respectivamente). A ausencia de flores ou presenca de pouquissimas flores foi um indicativo da melhor epoca de colheita da cv. Novirex visando maximizar o rendimento de vagens comerciais, independentemente da epoca de plantio. Nesta fase dos feijoeiros, as vagens, em media, haviam atingido o desenvolvimento maximo.

Performance of Amblyseius herbicolus on broad mites and on castor bean and sunnhemp pollen.

Amblyseius herbicolus (Banks) is found associated with broad mites Polyphagotarsonemus latus in crops such as chili pepper in Brazil. The species has a potential for controlling P. latus, but little is known about its development and reproduction on this pest as well as on other food sources. We studied biological, reproductive and life table parameters of A.herbicolus on three different diets: broad mites, castor bean pollen (Ricinus communis) and sunnhemp pollen (Crotalaria juncea). The predator was able to develop and reproduce on all diets. However, its intrinsic growth rate was higher on the diet of broad mites or on castor bean pollen than on sunnhemp pollen. Differences among pollen species may be due to their nutritional content. Feeding on alternative food such as pollen can facilitate the predator’s mass rearing and maintain its population on crops when prey is absent or scarce. Other strategies of using pollen to sustain predator population and reduce pest damage are discussed.

Caracterização morfológica e classificação da superfície foliar de pimentas quanto à presença de tricomas e domácias

3 EPAMIG-URZM, Vl. Gianetti 46, 36570-000 Vicosa-MG. ABSTRACT Morphological characterization and surface classification of chili pepper leaves considering trichomes and domatia The knowledge of morphological characteristics of plant leaves is important to study the interactions among plants, herbivores and natural enemies. Variations on such characteristics are determinant on the occurrence, abundance and diversity of organisms that exploit that habitat. The leaf surface of four Capsicum pepper species was characterized, focusing on the presence of trichomes and domatia. The objective is to identify possible mite resistance mechanisms on these plants. The classification key of pepper leaves was based on presence/absence, density and distribution of trichomes. The counting of trichomes was done in an area of 5 cm 2 , from the medium third of each leaf. We assessed the trichomes from the limb, ribs and domatia. The pepper species significantly differed on the density of domatia and trichomes present on the ribs and limbs of their leaves. A significant difference was observed on the total density of trichomes/ cm 2 and on the number of trichomes/domatia. From the five Capsicum species evaluated, only C. baccatum var. pendulum (hot pepper, variety girl finger pepper) does not have domatia neither trichomes in any part of its leaves. The highest domatia density was found on C. baccatum var. praetermissum, which has the highest trichome density in all leaf parts and the only one with significant density of limb trichomes. The variation of the presence, distribution and density of trichomes and domatia may be determinant on the occurrence of herbivorous and predatory mites on plants. Such structures can act as a resistance mechanism against herbivore mites or may favor the presence of predatory and fungivorous mites due to provision of shelter sites. We propose here a surface classification scale of chili pepper leaves varying from 1 to 5 taking into account the number and density of observed trichomes and domatia.