Bacillus thuringiensis chimeric proteins Cry1A.2 and Cry1B.2 to control soybean lepidopteran pests: New domain combinations enhance insecticidal spectrum of activity and novel receptor contributions

Two new chimeric Bacillus thuringiensis (Bt) proteins, Cry1A.2 and Cry1B.2, were constructed using specific domains, which provide insecticidal activity against key lepidopteran soybean pests while minimizing receptor overlaps between themselves, current, and soon to be commercialized plant incorporated protectants (PIP’s) in soybean. Results from insect diet bioassays demonstrate that the recombinant Cry1A.2 and Cry1B.2 are toxic to soybean looper (SBL) Chrysodeixis includens Walker, velvetbean caterpillar (VBC) Anticarsia gemmatalis Hubner, southern armyworm (SAW) Spodoptera eridania, and black armyworm (BLAW) Spodoptera cosmioides with LC50 values < 3,448 ng/cm2. Cry1B.2 is of moderate activity with significant mortality and stunting at > 3,448 ng/cm2, while Cry1A.2 lacks toxicity against old-world bollworm (OWB) Helicoverpa armigera. Results from disabled insecticidal protein (DIP) bioassays suggest that receptor utilization of Cry1A.2 and Cry1B.2 proteins are distinct from each other and from current, and yet to be commercially available, Bt proteins in soy such as Cry1Ac, Cry1A.105, Cry1F.842, Cry2Ab2 and Vip3A. However, as Cry1A.2 contains a domain common to at least one commercial soybean Bt protein, resistance to this common domain in a current commercial soybean Bt protein could possibly confer at least partial cross resistance to Cry1A2. Therefore, Cry1A.2 and Cry1B.2 should provide two new tools for controlling many of the major soybean insect pests described above.

Natural Enemies of Fall Armyworm Spodoptera frugiperda (Lepidoptera: Noctuidae) in Different Agro-Ecologies

Fall armyworm (FAW) Spodoptera frugiperda (J.E. Smith) and southern armyworm (SAW) Spodoptera eridania (Stoll) have become major threats to crops in Africa since 2016. African governments adopted emergency actions around chemical insecticides, with limited efforts to assess the richness or roles of indigenous natural enemies. Field surveys and laboratory studies were conducted to identify and assess the performance of parasitoids associated with spodopterans in Cameroon. FAW was the most abundant spodopteran pest. Telenomus remus (Nixon), Trichogramma chilonis (Ishi), Charops sp. (Szépligeti), Coccygidium luteum (Cameron), Cotesia icipe (Fernandez & Fiaboe), and Cotesia sesamiae (Cameron) are the first records in the country on spodopterans. Telenomus remus, T. chilonis, C. icipe, and Charops sp. were obtained from both FAW and SAW; C. luteum and C. sesamiae from FAW. The distribution of spodopterans, their endoparasitoids, and parasitism rates varied with host, season and location. In the laboratory, T. remus showed significantly higher parasitism on FAW than SAW, and significant differences in the development parameters between the two host eggs, with shorter development time on FAW. It induced significant non-reproductive mortality on FAW but not on SAW. Developmental parameters showed that C. icipe has a shorter development time compared to other larval parasitoids. Implications for conservative and augmentative biocontrol are discussed.

POTENTIAL OF MAIZE, MILLET AND RATTLEBOX TO BREAK THE CYCLE OF 𝘚𝘱𝘰𝘥𝘰𝘱𝘵𝘦𝘳𝘢 𝘦𝘳𝘪𝘥𝘢𝘯𝘪𝘢 (CRAMER) (LEPIDOPTERA: NOCTUIDAE)

This study evaluated the effect of different crops grown during soybean offseason on the development and reproduction of Spodoptera eridania (Cramer). The experiment was conducted in laboratory at 25°C±1°C, relative air humidity of 70%±10% and a 12h photophase. The plants evaluated were cotton (FMT 701), sunflower (Embrapa 122-V2000), rattlebox (Crotalaria spectabilis Roth), corn (Dekalb 370) and millet (DR-300). The less suitable hosts for the survival of S. eridania were rattlebox, corn and millet. Only cotton and sunflower the specie completed its development (egg to adult). Corn, millet and rattlebox were the crops that most affected the performance of S. eridania, and therefore they could potentially be used in the soybean offseason period to interrupt the life cycle of this species, and thus reduce population incidence during soybean season.

Spodoptera eridania (southern armyworm).

Spodoptera eridania is a polyphagous generalist feeder recorded on 200 plants species belonging to 58 botanic families. It is native to the USA and occurs throughout southern USA, Central and South America, and the Caribbean (Pogue, 2002). Due the fact that S. eridania occurs all across the USA and is present in many host plants, several regions around the world are in risk of invasion due to the global trade of vegetables, ornamental and aromatic plants, which can transport larvae and eggs. Even though it is not established in Europe, it has been detected on imported plants from the New World (Karsholt, 1994). The detection of S. eridania in Africa, demonstrates its high dispersal ability, indicating the importance of closely monitoring this species.

Inseticida biológico no controle de lagarta Spodoptera Eridania no cultivo da soja

O controle químico não tem apresentado eficiência em determinadas regiões brasileiras, devido ao hábito de lagartas Spodoptera eridania permanecer na região inferior das folhas, dificultando que a molécula química atinja o alvo. Diante disso, o objetivo do trabalho foi verificar a eficiência do produto biológico a base de Bacillus thuringiensis no controle da lagarta Spodoptera eridania. O trabalho foi realizado na fazenda Água Boa localizada no município de Paragominas-PA. O delineamento experimental utilizado foi inteiramente casualizado, com 4 tratamentos e 4 repetições, os tratamentos foram: 1 - Testemunha; 2 - Xentari + Klorpan (biológico); 3 - Dimax + Klorpan; 4 - Prêmio + Brutos. Os parâmetros avaliados foram nível de largatas e controle, desfolha, fitotoxicidade, peso de mil grãos, umidade, custo x benefício e produtividade. Os dados foram submetidos à análise de variância (ANOVA) e comparados pelo teste de Tukey, a 5% de probabilidade. O Inseticida biológico à base Bacillus thuringiensis, Xentari + Klorpan proporcionou um maior controle de lagartas Spodoptera eridania, melhor produtividade e rendimentoda soja, no município de Paragominas. Destaca-se que esse inseticida biológico proporcionou benefícios tanto para o produtor, no que se refere à produtividade e lucro, como para o meio ambiente.