Daniel Spagnol

Selectivity of herbicides registered for corn at the immature stages of Trichogramma pretio sum (Hymenoptera: Trichogrammatidae)

4 e SPAGNOL, D. 4 RESUMO - O controle quimico tem sido um dos metodos mais utilizados para o manejo de plantas daninhas na cultura do milho, no entanto o uso de herbicidas pode ocasionar efeitos adversos aos insetos beneficos, como os parasitoides de ovos. Nesse sentido, foi avaliada a seletividade de 12 herbicidas registrados para a cultura do milho para as fases imaturas de Trichogramma pretiosum em condicoes de laboratorio (temperatura de 25±1 oC, umidade relativa de 70±10% e fotofase de 14 horas). Os herbicidas foram diluidos em um volume proporcional a 200 L de agua por hectare e pulverizados sobre ovos de lepidoptero contendo formas imaturas do parasitoide em seu interior, nas fases de ovo-larva, pre-pupa e pupa. Avaliou-se, entao, a porcentagem de emergencia dos parasitoides e, em funcao da comparacao com a testemunha, classificaram-se os herbicidas em inocuo (classe 1, 99%). Os herbicidas Agrisato 480 SL, Finale, Glifos, Glifosato Nortox, Gliz 480 SL, Polaris, Roundup Original, Roundup Transorb, Roundup WG, Trop e Zapp Qi foram inocuos (classe 1) as diferentes fases imaturas de T. pretiosum e sao considerados seletivos ao parasitoide. Gramoxone 200, embora tenha sido inocuo para as fases de ovo-larva e pre-pupa, foi considerado levemente nocivo (classe 2) para a fase de pupa. Nesse sentido, para melhor compatibilizacao do manejo quimico das plantas daninhas e controle biologico de insetos, sugere-se que sejam utilizados, sempre que possivel, aqueles herbicidas que permitem maior sobrevivencia de T. pretiosum. Palavras-chave: controle biologico, controle quimico, efeitos colaterais, parasitoide de ovos, toxicidade, Zea mays. ABSTRACT - - Chemical control has been one of the most widely used methods for weed management in corn. However, the use of herbicides can cause adverse effects on beneficial insects, such as egg parasitoids. Thus, this work aimed to evaluate the selectivity of 12 herbicides registered for corn at the immature stages of Trichogramma pretiosum Riley, 1879 (Hymenoptera: Trichogrammatidae) under laboratory conditions (temperature 25±1 o C, relative humidity 70±10%; photoperiod 14 hours). The herbicides were diluted in a proportion of 200 L of water per hectare and sprayed on lepidopteran eggs containing immature forms of the parasitoids, at the egg-larva, prepupae and pupae stages. The emergence percentage of parasitoids was evaluated, and, when compared with the control, the herbicides were classified as harmless (class 1, 99%). The herbicides Agrisato 480 SL, Finale, Glifos, Glifosato Nortox, Gliz 480 SL, Polaris, Roundup Original, Roundup Transorb, Roundup WG, Trop and Zapp Qi were classified as harmless (class 1) at different immature stages of T. pretiosum, and considered selective to the parasitoid. Although harmless at the egg larva and prepupae stages, Gramoxone 200 was classified as slightly harmful (class 2) at the pupae stage. Accordingly, to better reconcile the chemical management of weeds with the biological control of insects, the use of herbicides allowing greater survival of T. pretiosum is suggested, whenever possible.

Persistência de agrotóxicos utilizados na cultura do milho ao parasitoide Trichogramma pretiosum Riley, 1879 (Hymenoptera: Trichogrammatidae)

The high yields in corn have been achieved due to various technical factors, being the pest control one of the most important. In this way, the objective was to evaluate the persistence of the pesticides used in corn field to the parasitoid Trichogramma pretiosum. It was evaluated the persistence of seven insecticides and three fungicides, which were separately diluted to 200L of water and sprayed on the vine leaves. These leaves were taken to the laboratory and used into cages at 3, 10, 17, 24 and 31 days, where remained confined the adults of the parasitoids to contamination. The adult mortality of T. pretiosum was measured according to the lower number of parasitized eggs of alternative host Anagasta kuehniella. The results were compared with the witness treatment and pesticides classified according to IOBC categorization. Four replicates for each treatment were used. The fungicides Opera, Priori Xtra and Folicur 200 EC were short life (class 1). The insecticides Match EC and Sumithion 500 CE were short life (class 1); Lorsban 480 BR and Safety were moderately persistent (class 3), and Engeo Pleno, Karate Zeon 50 CS and Tracer were persistent (class 4) to adults of T. pretiosum.

Prohexadione calcium reduces vegetative growth and increases fruit set of ‘Smith’ pear trees, in Southern Brazil

ABSTRACT: Prohexadione calcium (P-Ca) has been reported to effectively control shoot growth in several pear cultivars, but with a few reports about its efficiency under the climatic conditions of southern Brazil. Therefore, the objective of this study was to evaluate vegetative growth, production, and fruit quality of ‘Smith’ pear trees in response to the use of different rates of P-Ca in the climatic conditions of southern Brazil. The experiment was conducted during the 2013/2014 and 2014/2015 seasons, in a 6-year-old ‘Smith’ pear orchard, trained to a central-leader system, with spacing of 1.5 × 4.8 m, grafted onto Pyrus calleryana Decne. Different P-Ca rates were applied (100, 200, 300, and 400 mg·L –1 ) in different stages: first, in early spring for all treatments, and the others when shoot growth resumed (GR), but only for some treatments. Variables BASIC AREAS - Article Prohexadione calcium reduces vegetative growth and increases fruit set of ‘Smith’ pear trees, in Southern Brazil

GIBBERELLIC ACID REDUCES FLOWERING AND TIME OF MANUAL THINNING IN ‘MACIEL’ PEACH TREES

The thinning peach fruits is to reduce the load of the plant with the aim to improve the size, flavor and color of the remaining fruits. However, the practice of thinning requires high demand of manpower and become more expensive the production costs. The objective of this study was to evaluate the reduction of flowering buds and the time of hand thinning in ‘Maciel’ peach after gibberellic acid (GA3) application at different times and concentrations. The experiments were performed in the harvests of 2012 and 2013 in a commercial peach orchard located in the county of Morro Redondo, RS. The plants of cultivar Maciel, in 2012, were sprayed with four doses of GA3 0, 25, 75 and 125 mg L-1, at different times 20, 40 and 60 days after full bloom (DAFB). The number of flowering buds and consequently thenumber of flowers was reduced in the 2013 season after application of GA3 on the 2012 harvest. The manual thinning decreased with doses applied at 60 DAFB. The number of flowering buds and consequently the number of flowers was reduced in 2013. There was reduction of manual thinning when applied at 60 DAFB. The doses of 25, 75 and 125 mg L-1 applied at 60 DAFB resulted in a reduction of 50.1, 76.9 and 87.1%, respectively, at the time of hand thinning. When applied the dose of 25 mg L-1 of GA at 60 DAFB reduces the number of flowering buds and hand thinning time in the next cycle in ‘Maciel’ peach, without compromising production.