Impact of insecticides used to control Spodoptera frugiperda (J.E. Smith) in corn on survival, sex ratio, and reproduction of Trichogramma pretiosum Riley offspring

Abstract

Corn (Zea mays L.) is cultivated in large areas and considered one of the world's major cereal crops. There are several arthropod pests that can reduce its production such as the fall armyworm, Spodoptera frugiperda (J.E. Smith) (Lep.: Noctuidae), which is considered to be the main pest for corn. Fall armyworm is primarily controlled by insecticides. The use of biological control agents to manage this pest is growing with an emphasis on the egg parasitoid Trichogramma pretiosum Riley (Hym.: Trichogrammatidae). Thus, the aim of this research was to evaluate the impact of the following insecticides (g ai L -1 ) beta-cypermethrin (0.03), chlorfenapyr (0.60), chlorpyrifos (0.96), spinosad (0.16), etofenprox (0.10), triflumuron (0.08), alfa-cypermethrin/teflubenzuron (0.0425/0.0425), and lambda-cyhalothrin/thiamethoxam (0.11/0.083) on survival, sex ratio, reproduction, and T. pretiosum offspring. Distilled water was used as a control. Commercial insecticide formulations were diluted in distilled water. Bioassays used Anagasta kuehniella eggs treated with insecticides which were afterwards exposed to parasitism. Bioassays were conducted under controlled conditions at 25 ± 2 ºC, 70 ± 10% RH, and 12:12 h photoperiod. Alfa-cypermethrin/teflubenzuron, beta-cypermethrin, chlorpyrifos, chlorfenapyr, spinosad, etofenprox, and lambda-cyhalothrin/thiamethoxam reduced parasitism capacity of maternal generation females as well as the percentage of insect emergence from the F1 generation. Only triflumuron was selective for T. pretiosum and can be recommended along with this parasitoid in fall armyworm management programs in corn.

Lethal and Sublethal Effects of Insecticides Used on Citrus, on the Ectoparasitoid Tamarixia radiata

“…exiguum (Class 4). These results diverge from those found in this study because Souza et al [ 46 ] treated the host eggs before offering them to the parasitoids. This difference in methodology and in insect species used might account for the divergent the results.…”

“…In this study, etofenprox was considered slightly harmful or harmless (Class 2 and 1) for generations F 0 and F 1 , respectively. However, Souza et al [ 46 ] obtained different results for T . pretiosum , reporting etofenprox as moderately harmful (Class 3).…”

Selectivity of registered pesticides for the corn crop on immature stages of Trichogramma pretiosum (Hymenoptera: Trichogrammatidae)

“…The longevity of T. pretiosum females was similar at 24 and 48 hours post-treatment with the products and lowest with atrazine 48 hours post-treatment (9.60 ± 3.48 hours), with all the others and the controls classified as harmless (lower than 30% reduction) ( Table 2). The reduction in parasitism and emergence of T. pretiosum under the positive control (product containing λ-cyhalothrin + thiamethoxam) and the low impact on the longevity of this parasitoid agree with reports of low λ-cyhalothrin toxicity to T. pretiosum adults in terms of longevity 48 hours after parasitism on treated A. kuehniella eggs (Souza et al, 2013). Cyhalothrin sprayed onto the leaves of upland cotton, Gossypium hirsutum L. (Malvaceae) plants was innocuous to Trichogramma exiguum Pinto & Platner, 1983 females four days after treatment (Suh;Orr;Van Duyn, 2000).…”

Toxicity of some insecticides used in maize crop on Trichogramma pretiosum (Hymenoptera, Trichogrammatidae) immature stages

“…Sex ratio alterations caused by some pesticides, as verified in this study for F1 and F2 adults of T. pretiosum (Tables 2 and 5) were also observed by Moura et al (2004; and Souza et al (2013) for the same Trichogramma species, as well as by other researchers for Trissolcus grandis Thomson, 1861 (Hymenoptera, Scelionidae) (Novozhilov et al, 1973) and Bracon mellitor Say, 1836 (Hymenoptera, Braconidae) (O'Brien et al, 1985). However, the physiological basis that could explain these alterations is not clear.…”