Arbuscular mycorrhizal fungi (AMF) influences growth and insect community dynamics in Sorghum-sudangrass (Sorghum x drummondii)

Impact of Cover Crops on Insect Community Dynamics in Organic Farming

“…Cabbage grown on the cover crop treatment plots had significantly higher biomass than the control cabbage. This is consistent with the benefits of cover crops reported in the earlier studies [25,44,45]. It is also important to note that there was a significant difference between the height of the two cover crops, with sunn hemp being taller than cowpea [39,40].…”

“…These results can have major implications in devising integrated pest management strategies for growing cash crops in the next season. However, the temporal influence on the insect diversity during the same season warrants additional examination of herbivore-induced plant chemistry, which can certainly play a major role in influencing the insect community dynamics in the field [3,[24][25][26][27]. Our results suggest that herbivores had a more-or-less uniform affinity to the cover crops throughout the summer season, while the beneficial insects were mostly found in higher numbers during the early season.…”

“…Amongst these, beneficial insects comprising of predators, parasitoids, and pollinators were found to be more abundant earlier rather than later in the season, while no crop-specific effect was observed on their abundance. As plants emit a unique blend of volatile compounds induced upon herbivory, also known as herbivore-induced plant volatiles (HIPVs) [3,[25][26][27][28], studies suggest that HIPVs can selectively attract the natural enemies like predators and parasitoids of the insect pests feeding on the host plant. For instance, a United States Department of Agriculture study suggested that sorghum sudangrass, upon herbivory by aphids, attracts their predators while cowpea, upon damage by stink bugs, leaf-footed bugs, and aphids, can attract parasitoid wasps and other beneficial insects [29].…”

“…For sweep net collection, each of the cover crop treatments was swept (20 sweeps/plot) just before cover crop termination. The rationale behind using three different methods of sampling was to obtain comprehensive coverage of the community including insects and other arthropods at canopy and soil levels, including fliers and crawlers (for details, see [3,24,25]). After the experiment, all sampled insects were identified and grouped into guilds based on their functional roles: herbivores, predators, parasitoids, and pollinators.…”

“…Damage was measured for 50 randomly chosen plants in each of the 3 sunn hemp and 3 cowpea plots for a total of >300 plants. Damage was measured visually on a scale of 0 to 4, 0 indicating no visible damage to the plant while a 4 indicated physical damage was present on almost all leaves of the plant (see [25] for methodological details). Insect collection using the sweep net method consisted of sweeping an insect net (11' diameter) three times over the cover crop plot of each of the six chosen fields plus three control plots and placing the contents into a mason jar containing 70% isopropyl alcohol for further storage and identification.…”