Side-effects of pesticides used in irrigated rice areas on Telenomus podisi Ashmead (Hymenoptera: Platygastridae)

Abstract

Telenomus podisi Ashmead (Hymenoptera: Platygastridae) is an important agent for the biological control of stink bug eggs in irrigated rice areas and the best strategy for its preservation is the use of selective pesticides. The aim of this study was to know the side-effects of pesticides used in Brazilian irrigated rice areas on egg parasitoid T. podisi. We evaluated, under laboratory conditions, 13 insecticides, 11 fungicides, 11 herbicides, and a control (distilled water) in choice and no-choice tests. In the no-choice tests, the pesticides were sprayed at pre and post-parasitism stages (egg and larval stages of T. podisi). In the choice tests, sprays were conducted only at pre-parasitism stages. For all tests, we prepared cards with 25 eggs of the alternative host Euschistus heros (Fabricius) (Hemiptera: Pentatomidae) non-parasitized (pre-parasitism) and parasitized (post-parasitism), which were subjected to pesticide sprays. The parasitism and emergence rates of T. podisi were determined classifying the pesticides in terms of the reduction of parasitism or emergence rates compared to the control. The neurotoxic insecticide cypermethrin, lambda-cyhalothrin, zeta-cypermethrin, etofenprox, thiamethoxam, thiamethoxam + lambda-cyhalothrin, acetamiprid + alpha-cypermethrin, and bifenthrin + alpha-cypermethrin + carbosulfan were more harmful to T. podisi and, therefore, are less suitable for the integrated management of insect pests in irrigated rice areas.

Selectivity of Insecticides to a Pupal Parasitoid, Trichospilus diatraeae (Hymenoptera: Eulophidae), of Soybean Caterpillars

“…These insecticides do not affect adult insects as they are growth regulators inhibiting chitin synthesis [ 25 ]. This is similar to that reported for the insecticides lufenuron and novaluron from the same IRAC-appointed insecticide action group, specific to insect larvae and nymphs with the parasitoid Diachasmimorpha longicaudata (Ashmead, 1905) (Hymenoptera: Braconidae) [ 16 , 26 ]. The 100% mortality of T. diatraeae females after 24 h exposure to acephate classifies this insecticide as toxic [ 20 ].…”

“…Trichospilus diatraeae female mortality within 24 h from deltamethrin and thiamethoxam + lambda-cyhalothrin classifies these insecticides as mildly toxic to this natural enemy [ 20 ]. These insecticides, from the pyrethroid and neonicotinoid groups, act by keeping sodium channels open, causing hyperexcitation and blocking the insect’s nervous system and or binding to acetylcholine (ACh), transforming it into nAChRs and causing diverse symptoms, including hyperexcitation, lethargy and paralysis [ 26 ]. Pyrethroids and neonicotinoids act on the nervous system and respiration at all stages of insect development [ 27 , 29 ].…”

Differential impacts of pesticides on Euschistus heros (Hem.: Pentatomidae) and its parasitoid Telenomus podisi (Hym.: Platygastridae)

“…Adult parasitoids may be directly exposed to insecticide droplets during spraying or indirectly by toxic residues on the plant canopy, water droplets, nectar, or honeydew 43 , and are more sensitive to the effects of pesticides than the immature stages because the embryo is protected by the egg chorion during insect development 44 . Therefore, the RQ was used for the first time to evaluate the ecological risk of insecticide used to control E .…”

“…40 evaluated the toxicity of sublethal doses (CL 25 ) of the pyrethroids deltamethrin and cyfluthrin to the progeny of females of Telenomus busseolae Gahan (Hymenoptera: Platygastridae) and found no detrimental effects on insect emergence. However, studies with parasitoids of the Platygastridae family indicated that insects emergence decreased when immature stages were exposed to pesticides 41,44 . It is of note that our results do not allow determining whether the reduction in insect emergence is due to the direct effects of pesticides or the occurrence of other dysfunctions such as organ malformation 31 .…”

Selectivity of Insecticides Against Telenomus podisi Ashmead (Hymenoptera: Platygastridae) on Corn

“…adversely affect natural enemies and reduce the effectiveness of biological control. Several studies have shown adverse effects of chemicals on Telenomus remus (Carmo, A. F. Bueno, R. C. O. F. Bueno, Vieira, Gobbi, & Vasco, 2009;Vieira, Boff, A. F. Bueno, Gobbi, Lobo, & R. C. O. F. Bueno, 2012), Trissolcus sp., (González, Laumann, Silveira, Moraes, Borges, & Ferreira, 2013), Trichogramma galloi (Oliveira, Antigo, Carvalho, Glaeser & Pereira, 2013), Telenomus podisi (Smaniotto, Gouvea, Potrich, E. R. L. Silva, J. Silva & Pegorini, 2013;Turchen, Golin, Butnariu, Guedes, & Pereira, 2015;Pazini, Pasini, Seidel, Rakes, Martins, & Grutzmacher, 2017), among other egg parasitoids.…”