Aphids, Aphis fabae Scopoli and Myzus persicae Sulzer are important pests of sugar beet, causing direct damage through phloem feeding as well as transmitting Beet Yellows Virus (BYV). Both species have a very broad host range including many wild plant species. As chemical control options are increasingly constrained by insecticide resistance and legislation, it is crucial to find alternative methods of pest regulation. Conservation biological control can be used to augment natural enemy populations in arable fields by manipulating the ecological infrastructure around the field. This study investigated highly diverse, native flower strips for conservation biological control in sugar beet crops. A split plot design was used to compare the effects of flower strips with a grass margin control. Assessments of aphids and natural enemies were conducted in three transects in each treatment, at 2, 6, 12 and 24 m from the margin. Abundance and species richness of foliar predators was found to be higher near the flower strip up to 12m from the margin. Myzus persicae was generally scarce in the fields, with no effect of the flower strip in either year, and no symptoms of BYV were found in any of the fields. The mean colonization by A. fabae was significantly higher adjacent to the flower strip in 2023 but did not exceed the damage threshold in either treatment. The aphid to predator ratio was significantly lower on plants adjacent to flower strips in 2022, indicating that flower strips enhanced predator abundance relative to aphid populations. The present study shows that flower strips promote foliar predator populations in the adjacent fields and can lead to a higher predator to aphid ratio indicating an aphid control potential but did not significantly affect the already low aphid densities in the two years of study.
The fall armyworm, Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae) is an invasive pest that has recently emerged as a serious threat to maize production in Iran. The cultivation of resistant plants is one of the most effective strategies for managing S. frugiperda. In the current study, variation in the resistance of 10 commercial maize hybrids, including BC678, BK65, BK66, SC201, SC260, SC400, SC410, SC704, SC705, and SC706 to S. frugiperda was investigated through studying the life history and population growth parameters, feeding indices, and enzymatic activities of the pest. Moreover, the levels of nutrients and anti-nutrients in the leaves of field-grown maize hybrids were quantified. According to the results, the development time of S. frugiperda was longest on SC201 and shortest on BK65. The lowest and highest fecundity were on BK66 and SC410, respectively. The intrinsic rate of increase (r) ranged from 0.139 to 0.187 day-1 on various maize hybrids, with the lowest value obtained on BK66. The feeding efficiency was significantly decreased on SC201 and BK66. The relative growth rate (RGR) varied from 0.133 to 0.190 mg mg-1 day-1 on various treatments, being lowest on BK66 and higher on BC678 and SC410. The relative metabolic rate (RMR) and metabolic cost (MC) were maximum on BK66 and minimum on SC410. The suppressed digestive enzymes activities along with the enhanced antioxidant enzymes activities in S. frugiperda larvae were observed on BK66. Analysis of nutrient and anti-nutrient contents revealed significant variation among maize hybrids. The cluster analysis further classified SC410 and BK66 as the most and least suitable hybrids for the pest, respectively. These findings can be incorporated into integrated management strategies to protect maize production in S. frugiperda-infested regions.
RNA interference (RNAi) is a promising strategy for sustainable management of Helicoverpa armigera, but its biological efficacy is strongly influenced by the developmental stage at which dsRNA is applied. Identifying the optimal larval stage for RNAi intervention is therefore critical for maximizing pest management efficacy rather than transcript suppression alone. The present study evaluated the stage-specific effects of silencing Glucosamine-6-phosphate N-acetyltransferase (HaGNA), a key gene in chitin biosynthesis pathway. Double-stranded RNA targeting HaGNA was injected into 3rd, 4th, and 5th instar larvae at a uniform cumulative dose of 100ng dsRNA mg-1 body weight followed by two booster injections for improved RNAi efficiency. Silencing of HaGNA significantly reduced survival, growth, chitin content and developmental fitness while inducing severe molting defects, pupal abnormalities and adult deformities. RNAi of HaGNA caused highest transcript knockdown in 5th instar (52.28%), while prominent biological effect was observed in 3rd instar accompanied by highest larval mortality (64.44%) and chitin depletion (27.63%) with strongest growth inhibition and pronounced developmental delays. Cox proportional hazards analysis revealed an approximately 11-fold increase in mortality risk following HaGNA silencing. Susceptibility declined progressively with larval age, whereas later-instar treatments shifted mortality toward pupal stages and increased adult malformations. Overall, the third larval instar represents the optimal developmental stage for dsRNA application, providing maximal biological efficacy, thereby suggesting HaGNA as a promising target for RNAi-based pest management.
Weedy rice (Oryza sativa f. spontanea) is a problematic weed in direct-seeded rice fields, causing substantial rice yield losses. In this study, greenhouse and field experiments were conducted to systematically evaluate the effects of water depths, flooding durations, burial depths, and preemergence herbicides on germination and growth of weedy rice. Results indicated that water management alone (3-10 cm water depth maintained for 3-14 d) did not significantly inhibit the emergence rate of weedy rice, with the highest fresh weight control efficacy reaching only 36.1%, indicating that flooding alone is insufficient for effective control. However, increasing burial depth under flooded conditions significantly inhibited weedy rice germination. At a 4-cm burial depth, emergence was reduced from 91.7% (at 2-cm depth under 3-d flooding) to less than 5% when flooding was extended to 14 d. Extending the flooding duration further reduced the burial depth required for 50% suppression from 3.2 cm (non-flooded) to 1.4 cm (14-d flooding). Under water management, the application of preemergence herbicides demonstrated notable efficacy. Flufenacet (92.3 g ai ha-1) achieved 100% control of weedy rice after a 3-d presowing water retention period. The mixture of oxadiazon + triafamone (390.0 + 39.0 g ai ha-1) provided 98.0% control efficacy after 7 d of flooding. In field trials, both herbicide treatments provided over 73.0% control of weedy rice plants. In conclusion, although flooding alone has limited efficacy, combining it with moderate soil burial (>= 4 cm) or with application of effective preemergence herbicides such as flufenacet or oxadiazon + triafamone can significantly inhibit the germination and growth of weedy rice. These findings provide technical support for the integrated management of weedy rice in direct-seeded rice systems.
The corn leafhopper, Dalbulus maidis, is a major pest of corn crops as it transmits the corn stunt disease complex (CSDC) pathogens. Chemical control has become less effective due to the selection of resistant populations. Insect growth regulators (IGRs) of both botanical and synthetic origins offer a viable alternative, affecting nymphal development and exhibiting potential sublethal effects. We evaluated the toxicity of these products on D. maidis eggs and nymphs in the lab, and, in the field, assessed their impact on pest abundance, CSDC severity, and corn yield components when applied at different times. Our results showed that the buprofezin-based insecticide reduced nymphal emergence and survival in D. maidis. Bioexos Plus (R) (neem-based) prolongs the nymphal stage and has a dose-dependent phagodeterrent effect, while Fitoneem (R) lowers the reproductive potential of the corn leafhopper. In the field, no significant differences in pathogen incidence or severity were observed; however, the combination of Fitoneem (R) with methomyl in the 4th sequential application and buprofezin applied alone in the 3rd application significantly reduced the D. maidis adult population compared with the untreated control. These findings suggest that sublethal effects of the evaluated IGRs likely influence the population dynamics of D. maidis in corn production systems.
