Insecticidal effect of garlic essential oil on Diatraea saccharalis (Fabricius, 1794) (Lepidoptera: Crambidae) eggs

Abstract

Studies have reported the resurgence of insect pests that are resistant to chemical and, more recently, to biological pesticides. Diatraea saccharalis is one of the main pests in sugarcane crops and responsible for large losses in the sugar and alcohol industries. The use of plant extracts including garlic essential oil (Allium sativum) which contains allicin, a compound that interferes with biochemical and physiological factors of target insects is considered an efficient and sustainable alternative for integrated pest management. The objective of this study was to test the toxicity of garlic essential oil on D. saccharalis eggs by analyzing rates of unhatched eggs, changes in external morphology, and esterases profile, enzymes related to insect resistance. For this, 24, 48, and 72-h-old eggs were immersed in 0.1, 0.5, and 1% garlic essential oil solutions for 2 min. Observations on embryonic development were made every 24-h for 72-h. Data on unhatched eggs were collected 288-h after treatments. For the esterases profile, eggs at 24-h after treatment with 1% solution were used. Eggs at 24-h-old, showed the least resistance to bioinsecticide, being that, 24-h after treatments with solutions 0.1, 0.5, and 1%, unhatched rates 80, 91.7, and 89.2%, respectively. The absence of embryos, ruptures, and protrusions on the chorionic region, and partial inhibition of EST-9, 10, and 11 were observed 24-h after the bioassays. These results demonstrate that garlic essential oil affects D. saccharalis eggs, partially inhibiting enzymes related to the insect immune system and can be used as a sustainable alternative for the integrated management of this insect pest.

Potential of Two <i>Metarhizium anisopliae</i> (Clavicipitaceae) Isolates for Biological Control of <i>Diatraea saccharalis</i> (Lepidoptera: Crambidae) Eggs

“…Consequently, the toxins and enzymes released by M. anisopliae isolate MT may activate cell death in insects. Eggs of D. saccharalis express different esterases at different ages [31] [49], which activate metabolic processes crucial to embryonic development and survival [50]. The melanization process observed in this study is similar to those described by other authors who treated D. saccharalis eggs treated with different formulations (essential oil and entomopathogens) [31] [32] [51].…”

“…Eggs of D. saccharalis express different esterases at different ages [31] [49], which activate metabolic processes crucial to embryonic development and survival [50]. The melanization process observed in this study is similar to those described by other authors who treated D. saccharalis eggs treated with different formulations (essential oil and entomopathogens) [31] [32] [51]. Protease controls the melanization process [43] [52] and activates the serine protease cascade.…”

“…The presence of these enzymes in lepidopteran eggs was confirmed by Canazart et al [31], Kanost and Clem [52], and Maki and Yamashita [55].…”

“…This result is superior to the inviability potential of Blissus Antilles (Hemiptera: Lygaeidae) eggs (24-h old) infected by the ESALQ818 isolate (10 4 conidia/mL), at 96.7% [40]. Other studies have evaluated the mortality of D. saccharalis eggs treated with different solutions: Daquila et al [32] observed 34.98% inviability in eggs (0 -24-h old) infected by Bacillus thuringiensis isolate Aizawai GC-91 (Bacillales: Bacillaceae) and Canazart et al [31] observed that the alternative control with garlic essential oil (0.5%) made more than 60% of the eggs unfeasible.…”

“…The chorion of D. saccharalis eggs has a thin and translucid structure [31], formed by two structures, the exochorion and endochorion [32]. These structures are synthesized by ovarian follicular cells [46].…”