Abstract: A two-year field study was conducted using canola to check the efficacy of
different soil amendment treatments (SAT), i.e., with elemental sulfur (ES), bio-sulfur (BS),
and compost (Cp) mixtures against insecticide-treated (Carbosulfan) and untreated controls
regarding aphid populations. The results of the experiment revealed that ES treatments
significantly reduced aphid abundance, followed by Cp and ES+Cp. However, BS improved
aphid herbivory. The number of siliques, seeds, thousand-seed weight, and yield were
improved with a trend of ES+Cp > Cp > BS+Cp. Similarly, physiological mechanisms
revealed the regulation of nutrient and phenolic contents in canola with ES improving
sulfur, BS nitrogen, Cp, and ES+Cp calcium, and BS+Cp enhancing phosphorus, potassium,
iron, and zinc. Furthermore, RP-HPCL indicated that ferulic acid was highest in insecticide-
treated plot. Similarly, Cp improved quercetin and gallic acid; ES+Cp caffeic, chlorogenic,
m-coumaric, and sinapic acid; and BS+Cp enhances syringic, vanillic, ferulic, p-coumaric,
and cinnamic acid. The analysis regarding health risk assessment revealed among different
SAT, ES+Cp significantly reduced the Hazardous Quotient (HQ) of Cu and Zn. However,
further research is still needed to explore SAT’s potential to remediate other heavy metal
stresses with possible implications for pest management in different field crops.
Introduction
Urbanization and certain other anthropogenic activities are contaminating agricultural
lands on a wide scale [1]. No country in the world is totally free from such hazardous
impacts of industrialization, where effluents, industrial wastes, and sewage water are
affecting agricultural lands, either directly or indirectly [2]. Synthetic pesticides and
chemical fertilizers are also contributing to heavy metals (HMs) contamination in soils [3].
Due to limited land resources, farmers cannot quit growing crops on such contaminated
soils, especially in developing or underdeveloped economies. About 16% of land in China
is contaminated with HMs, and a higher percentage is anticipated for countries like India
Plants 2025, 14, 1110 https://doi.org/10.3390/plants14071110
Plants 2025, 14, 1110 2 of 26
and Pakistan [3,4]. Crops cultivated on such soils are overloaded with HMs and other
harmful elements that pose serious threats to human health, particularly in children [5].
Additionally, the level of insect herbivory and their impacts on crop plants may also be
affected by heavy metal contamination and effluent pollution [6].
Canola or rapeseed Brassica napus L. (Brassicales, Brassicaceae) is the second most
important vegetable oil crop in the world [7,8]. Aphids (Aphididae: Homoptera) are a
major pest of canola and other field crops at the global level [9]. They feed on leaves,
inflorescence, stems, and pods of canola and cause heavy yield losses. A heavy infestation
could reduce yield by up to ~75% [10]. The management of aphids relies primarily and
heavily on insecticides, but they have numerous concerns and implications for the environ-
ment, specifically contaminating the water reservoirs [11], trans-generational impacts on
biocontrol agents [12], and bioaccumulation of phytotoxic metals [13]. Hence, there is an
urgent need to look for other environmentally friendly pest management approaches
Soil amendment treatments (SAT) are reportedly involved in mitigating insect her-
bivory through the acquisition of antibiotic or antixenotic properties. Among the SAT,
sulfur is considered an important component of various pesticides [7,14]; it could reduce
insect herbivory by improving the defense mechanisms of crop plants [15]. It had been
reported that the use of sulfur against grapevine moth (Lobesia botrana) reduced the survival
of female moths by 43%, egg laying by 80%, emergence of neonates by 10%, and larval
settlement on treated berries by 55% [16]. Similarly, among dustable and wettable formu-
lations of sulfur, the former significantly reduced the infestation levels and oviposition
preference of Tuta absoluta in tomato seedlings [17]. The application of elemental and
bio-sulfur also hinders different fitness parameters of aphids (Brevicoryne brassicae) feeding
on canola crop. Furthermore, sulfur treatments significantly affect the reproduction time,
effective fecundity, relative growth rate, intrinsic rate of natural increase, and generation
time of tested pest [7,9]. Similarly, sulfur could also enhance the quality, yield, and nitrogen
utilization of crop plant [7,18]. Sienkiewicz-Cholewa and Kieloch [19] reported that the
number of pods, seeds, seed weight, and seed yield per plot was higher in sulfur-treated
canola than in untreated controls. Similarly, Abdallah et al. [20] showed that the application
of sulfur improved seed yield, oil yield, and nitrogen-use efficiency of canola
