Evaluation of artificial diets based on different legume seeds on the nutritional physiology and digestive function of Helicoverpa armigera (Hübner)

Helicoverpa armigera (Hübner) is considered a serious agricultural pest worldwide. We explored the effects of artificial diets containing ten legumes, including broad beans (Shadan, Feyz, Saraziri, Barekat, and Mahta cultivars), white kidney beans (Dehghan cultivar), red kidney beans (Goli cultivar), common beans (Khomein cultivar), cowpeas (Mashhad and Arabi cultivars) on the feeding responses of H. armigera by quantifying specific primary and secondary metabolites in the studied legumes and determining larval nutritional indices and digestive enzyme activities. The results showed that the highest efficiency of conversion of digested food (ECD) and relative growth rate values (RGR) of whole larval instars were obtained in the Dehghan and Goli cultivars. However, the lowest values of ECD and RGR were observed in the larvae fed on the Khomein and Mahta cultivars. The highest proteolytic and amylolytic activities of larvae were found on the Dehghan and Mashhad cultivars. The highest and lowest values of standardized insect-growth index and index of plant quality were observed in larvae feeding on the Dehghan and Khomein cultivars, respectively. Additionally, significant variations in phytochemical metabolites were recorded among the studied legume cultivars. Significant negative or positive correlations were also found between feeding characteristics and enzymatic activities of H. armigera with the biochemical composition of the studied legumes. The cluster analysis results revealed that artificial diets containing Mahta and Khomein cultivars were unsuitable for H. armigera, and can be used as candidates for integrated pest management programs or for screening insect inhibitors to produce genetically modified pest-resistant plants.

Identification of Cellulolytic Bacteria from Guts of Microcerotermes diversus Silvestri (Isoptera: Termitidae) in Southern Iran

Termites are a large and important group of insects in terrestrial ecosystems that decompose lignocelluloses. Among these, Microcerotermes diversus Silvestri (Termitidae) is a destructive invasive pest in many tropical and subtropical regions. In the present study, M. diversus specimens were collected from traps in Ahvaz, Bandar Abbas, Kish, and Khark Islands. Sample suspensions were prepared in 5-ml DH₂O and cultured on nutrient agar (NA) medium. All 47 representative bacterial isolates were evaluated for cellulolytic activity by growing them on cellulose Congo-red agar medium. Based on some key phenotypic characteristics, the isolates were tentatively identified at the genus level. These were confirmed by 16S rRNA analysis using a universal primer pair (P1/P6). Sequence alignments revealed that most of the isolates are novel species so far found in the termite guts. Results showed that some of the isolates are common for all surveyed areas. However, there were significant differences in their numbers and degree of cellulolytic activity. The species reported here for the first time for termites of Iran are Bacillus wiedmanii, B. paramycoides, Elizabethkingia anophelis, Lysinibacillus pakestanensis, Pseudomonas hibiscicola, Actinetobacter pitti, A. venetianus, and Ochrobactrum anthropi.

Horizontal Transmission of the Entomopathogen Fungus Metarhizium anisopliae in Microcerotermes diversus Groups

An experiment was carried out in order to investigate fungal conidia transmission of Metarhizium anisopliae (Metschnikoff) Sorokin from vector (donor) to healthy Microcerotermes diversus Silvestri (Iso.: Termitidae) and determine the best donor/concentration ratio for transmission. After preliminary trials, concentrations of 3.1 × 10⁴, 3.9 × 10⁵, 3.2 × 10⁶ and 3.5 × 10⁸ conidia mL⁻¹ were selected for testing. The experiment was performed at three donor : Recipient ratios of 10, 30 and 50%. The highest mortality of recipient workers was observed after 14 days at the concentration of 3.5 × 10⁸ conidia mL⁻¹ and donor ratio of 50%. The mortality of recipient workers was less than 20% at all concentrations at a donor ratio of 10%. Our observations indicate social behavior of M. diversus, such as grooming, can be effective in promoting epizootic outbreaks in a colony. While the current results suggest good potential for efficacy, the use of M. anisopliae as a component of integrated pest management of M. diversus still needs to be proven under field conditions.

Foraging population and territory estimates for Microcerotermes diversus (Isoptera: Termitidae) through mark-release-recapture in Ahwaz (Khouzestan, Iran)

Microcerotermes diversus Silvestri (Isoptera: Termitidae), an important pest in Ahwaz (Khouzestan, Iran), causes serious economic damage to wooden products in buildings. In this study, we determined the foraging populations and territories of this species using mark-release-recapture techniques. Based on both the weighted mean model and Lincoln index methods, mean termite foraging population estimates for two colonies, A and B, were 2,984,489 +/- 258,802 and 326,134 +/- 8,713, respectively. Estimates with the Lincoln index were 2,731,229 +/- 813,081 for colony A and 321,493 +/- 138,499 for colony B. Estimated horizontal foraging territories for colonies A and B were 25.59 and 44.16 m2, respectively. The maximum and minimum linear foraging distances were 5.40 and 2.14 m for colony A and 9.14 and 1.86 m for colony B, respectively. Our data expand the knowledge about the biology, ecology and behavior of M. diversus.

Laboratory evaluation of Flurox, a chitin synthesis inhibitor, on the termite, Microcerotermes diversus

Microcerotermes diversus (Silvestri) (Isoptera: Termitidae) is the most economically destructive termite in structures in southwest Iran. One sustainable control strategy that usually helps to reduce subterranean termite damage in buildings, is the use of insect growth regualtors in a suitable bait matrix that are safe to the user and the environment. In the laboratory assays described here, the delayed toxicity of Flurox, a chitin synthesis inhibitor, to M. diversus was evaluated under force-feeding and choice trials. Flurox induced worker and nymph mortality and incomplete ecdysis in nymphs of M. diversus under no-choice and two-choice feeding tests. These adverse effects may cause disruption of the caste balance in M. diversus, leading to the collapse of the colony. These assays determined concentrations of Flurox that can be used in bait formulations.