The endoparasitoid Tetrastichus howardi (Olliff) (Hymenoptera: Eulophidae) can be reared with the alternative host Tenebrio molitor (Linnaeus) (Coleoptera: Tenebrionidae). Host storage at low temperatures can regulate parasitoid production and demand in biological control programs. The life cycle (egg to adult), parasitism and emergence percentage, number of parasitoids emerged per host pupae, sex ratio, and longevity of the T. howardi offspring per T. molitor pupa were evaluated after low temperature storage of this host for different periods, and its immature (pupae) in T. molitor pupae for 5 periods at 10.3 °C. Tenebrio molitor pupae stored at 0.5 ± 0.09 °C and 2.7 ± 0.11 °C for 10 and 20 d, respectively, were adequate to produce T. howardi. The biological characteristics of this parasitoid were better with T. molitor pupae stored at 0.5 ± 0.09 °C and 2.7 ± 0.11 °C for 10 and 20 d. Tetrastichus howardi immature (pupae) can be stored in T. molitor pupae for 10, 20, 30, 60, and 90 d at 10.3 °C, preferably in pupae of this host for 10 d to produce the adults of this parasitoid for biological control programs. These results contribute to overcoming 1 of the difficulties encountered in the mass production of parasitoids. Therefore, the conservation of T. molitor pupae in low temperatures can be used to increment of population of T. howardi in mass production for pest control programs.

Parasitoids control insect pests, but their number per host affects their efficiency. The objective of this work was to evaluate the best density of Tetrastichus howardi (Olliff, 1893) (Hymenoptera: Eulophidae) individuals parasitizing fourth instar Plutella xylostella (Linnaeus, 1758) (Lepidoptera: Plutellidae) larvae in greenhouse conditions. These larvae were exposed to parasitism by T. howardi females with 1:1, 3:1, 6:1, 9:1, 12:1, 15:1 and 18:1 parasitoid/host ratios with 10 replications during 96 hours. After this period the larvae were kept on host plants (Brassica oleracea) until pupa formation. Tetrastichus howardi parasitized and reproduced in P. xylostella larvae at all its densities tested, but with higher values, 84% and 10 ± 2.4 individuals, respectively, with 9:1 parasitoids/host. Nine T. howardi females per P. xylostella larvae are the adequate number to manage this insect pest.

Selectivity is an important aspect of modern insecticides to be able to target pests whilst maintaining beneficial entomofauna in the crop. The present objective was to assess the selectivity of different insecticides for the pupal parasitoid of soybean caterpillars, i.e., Trichospilus diatraeae Cherian & Margabandhu, 1942 (Hymenoptera: Eulophidae). Acephate, azadirachtin, Bacillus thuringiensis (Bt), deltamethrin, lufenuron, teflubenzuron and thiamethoxam + lambda-cyhalothrin at the highest recommended concentrations for the soybean looper Chrysodeixis includens (Walker, [1858]) (Lepidoptera: Noctuidae), as well as water in the control, were used against the pupal parasitoid T. diatraeae. The insecticides and the control were sprayed on the soybean leaves, which were left to dry naturally and placed in cages with T. diatraeae females in each one. Survival data were submitted to analysis of variance (ANOVA) and the means were compared using Tukey’s HSD test (α = 0.05). Survival curves were plotted according to the Kaplan–Meier method, and the pairs of curves were compared using the log-rank test at 5% probability. The insecticides azadirachtin, Bt, lufenuron and teflubenzuron did not affect T. diatraeae survival, while deltamethrin and thiamethoxam + lambda-cyhalothrin presented low toxicity and acephate was highly toxic, causing 100% mortality in the parasitoid. Azadirachtin, Bt, lufenuron and teflubenzuron are selective for T. diatraeae and could be used in IPM programs.

The maize weevil, Sitophilus zeamais Motschulsky, 1885 (Coleoptera: Curculionidae), is one of the primary insect pests affecting maize in Brazil. Due to the limited availability of active compounds for insect control, there is a pressing need to explore alternative sources of resistance, potentially harboring genetic reservoirs for material improvement. This study aimed to identify resistant maize varieties by assessing S. zeamais emergence, amylase enzyme inhibitors, susceptibility indices, and nutritional analysis of the grains. Eight maize varieties, namely Azteca, Caiano, Colorado, Maisena, Oaxaca, Oito Carreira, Palha Roxa, and Rajado, were evaluated. Unsexed S. zeamais adults were confined in 250 mL plastic bottles containing grains of each maize variety for ten days, with ten replications for copulation and oviposition. After the incubation period, the insects were removed, and the infested grains stored for an additional thirty days. The emergence of S. zeamais was monitored every two days, and the pots were discarded after three consecutive evaluations without emergence. The amylase enzyme inhibitors, as a potential factor influencing resistance, was also analyzed. The susceptibility index was the primarily parameter used to evaluate resistance of maize varieties to S. zeamais adults. The Colorado, Oaxaca, and Oito Carreira maize varieties were resistant through antibiosis and the Azteca, Caiano and Rajado were moderately resistant. In contrast, the Maisena and Palha Roxa varieties were susceptible to S. zeamais. The Azteca variety was moderately resistant, despite its high levels of amylase enzyme inhibitors.

The use of botanical insecticides is a sustainable alternative for the regulation of Plutella xylostella (Linnaeus, 1758) (Lepidoptera: Plutellidae) in brassica crops. Similarly, biological control with parasitoids can be an effective tool when integrated with bioinsecticides. However, the safety of natural insect enemies must be prioritized within pest control programs. The objective was to evaluate the effects of the water-based extracts of Serjania erecta Radlk (Sapindaceae) and Serjania marginata Casar (Sapindaceae), at 5% and 10% concentrations, on the reproduction of Tetrastichus howardi (Olliff, 1893) (Hymenoptera: Eulophidae) in larvae of P. xylostella, topically treated with extracts. In addition, we evaluated the survival of adult females of T. howardi exposed to the respective extracts of Serjania spp. For this purpose, two bioassays were conducted. In the first, 4th instar larvae of P. xylostella were selected, and 20 μL of each treatment was applied topically (S. erecta 5%, S. erecta 10%, S. marginata 5%, S. marginata 10%, distilled water) in each larva and then exposed to T. howardi parasitism for 48 hours. The percentage of parasitism and emergence (%), life cycle length (days), total number of progeny, sex ratio and adult longevity were evaluated. In the second bioassay, the ASPECLE (Evaluation of Pesticide Selectivity under Extended Laboratory Conditions) system, adapted from the International Organization for Biological Control (IOBC) standard model, was used. In this bioassay, five cabbage leaf disks were introduced in each glass cylinder of the ASPECLE system, duly treated with distilled water, aqueous extracts of S. erecta and S. marginata, at concentrations of 5% and 10%, or acephate. Subsequently, ten adult females of T. howardi were released in each cylinder and the system was activated. Parasitoid survival was evaluated for 24, 48, 72, 96 and 120 hours. The aqueous extracts of S. marginata and S. erecta at concentrations of 5% and 10% did not interfere in the parasitism of T. howardi on 4th instar larvae of P. xylostella. Field experiments should be developed to prove the negative effect of aqueous extracts of S. marginata and S. erecta on other biological characteristics of T. howardi. As a precaution, releases of T. howardi and sprays of aqueous extracts of S. marginata and S. erecta should be made at different times for the biological management of P. xylostella.

Optimizing mass-rearing systems using alternative hosts is essential for successful biological control programs. This study evaluated the effect of foundress density on the biological parameters of Tetrastichus howardi (Olliff) (Hymenoptera: Eulophidae) reared on pre-pupae and pupae of Anticarsia gemmatalis Hübner (Lepidoptera: Erebidae). Hosts were individually exposed to six parasitoid densities (1, 5, 10, 15, 20, and 25 females/host) for 24 h under laboratory conditions. Tetrastichus howardi successfully parasitized both developmental stages across all densities. Parasitism and emergence rates reached 100% at densities ≥ 10 females/host. The egg-to-adult development period decreased as foundress density increased, indicating intraspecific competition. Total progeny peaked at the 25:1 density, yielding 389.4 individuals per pre-pupa and 414.0 individuals per pupa. Conversely, individual female productivity was inversely proportional to density. The sex ratio remained highly female-biased (~0.80) across all treatments, and female longevity (~9 days) was not compromised. In conclusion, A. gemmatalis pre-pupae and pupae are highly suitable alternative hosts for T. howardi multiplication. For optimized mass production, a foundress density of 5 to 10 females per host is recommended to maximize high-quality progeny yield.