Abstract
ABSTRACT Adverse weather conditions, or mechanical problems and decrease in the application rate, may increase the storage time of the spray solution in the sprayer tank. This study aimed to assess the effect of the phytosanitary spray solution storage on the germination of Beauveria bassiana conidia, with or without agricultural adjuvants. A completely randomized design was used, in a 13 x 5 factorial scheme, consisting of thirteen storage times (0, 4, 8, 12, 16, 20, 24, 28, 32, 36, 40, 44 and 48 h) and five compositions for the spray solution (B. bassiana, B. bassiana + Helper Neutrum, B. bassiana + TA-35, B. bassiana + Nimbus and B. bassiana + Orobor). The biological spray solution containing B. bassiana conidia and no adjuvants remained viable for use after preparation and the conidial germination decreased 9.2 times after 48 h when an adjuvant was added.
Highlights
Brazil is the largest producer and second largest consumer of coffee worldwide (ICO 2018), with an estimated production of 44.97 million 60-kg bags (Arabica and Robusta) in 2018 and a planted area of around 2.2 million hectares
The conidial germination was influenced by the spray solution composition as a function of the storage time and used adjuvant
Including adjuvants in the spray solution may increase the control efficacy; knowledge regarding the interaction between adjuvants and entomopathogenic fungi is still incipient, and research on the topic is vital to aid in the decision making in the field and increase the application efficiency and treatment efficacy without losing the germination characteristics of the fungal spores
Summary
Brazil is the largest producer and second largest consumer of coffee worldwide (ICO 2018), with an estimated production of 44.97 million 60-kg bags (Arabica and Robusta) in 2018 and a planted area of around 2.2 million hectares. The estimated production in the Minas Gerais state in 2017 was 24.45 million bags, 24.1 million of which were Coffea arabica L. Annual economic losses caused by this insect are estimated at USD 287 million in Brazil alone (Oliveira et al 2012). The most widely used control methods are chemical and biological. Among the fungi used for its biological control is Beauveria bassiana (Bals.) Vuill., which has been reported attacking the beetle in several countries where it occurs naturally (Neves & Hirose 2005). Jenkins & Grzywacz (2000) reported that fungal and viral biocontrol agents have not yet reached a level of efficacy comparable to that of chemical insecticides or the most widely used bacterial antagonist, Bacillus thuringiensis
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