The Culex pipiens complex is a major and prevalent pest of dipterans for the most part of the world. The addition of sub-lethal quantities of chemical toxicants, such as fungicides and herbicides, can change the toxicity of certain insecticides on mosquito larvae. Hence, the purpose of the current study was to evaluate toxicity of certain insecticides individually and in combination with the sub-lethal concentrations of myclobutanil (1 µg ml-1 ) or S-metolachlor (0.140 µg ml-1 ) against C. pipiens larvae after 24, 48 and 72 h of exposure. Depending on the combination of the sub-lethal concentrations of S-metolachlor and myclobutanil, as well as the LC50 values of each studied insecticide, the insecticides exhibited distinct interaction reactions (e.g., antagonistic and/or synergistic effects) on C. pipiens larvae. Permethrin mixed with myclobutanil or S-metolachlor at sub-lethal concentrations produced a synergistic effect and enhanced permethrin's toxicity on C. pipiens larvae during exposure durations (except for the sub-lethal concentration of S-metolachlor after 72 h). On the other hand, following exposure times, combining imidacloprid or cyromazine with sub-lethal concentrations of myclobutanil or S-metolachlor was an antagonistic impact and reduced the toxicity of both insecticides on C. pipiens larvae. Only after 24 h of exposure did the sublethal concentrations of myclobutanil or S-metolachlor increase the lethality of indoxacarb; however, after 48 and 72 h of exposure, they decreased the toxicity of indoxacarb. It will be worthwhile to evaluate the impact of insecticides on fish and mosquito larvae when sub-lethal levels of herbicides and fungicides are present.

Tebuconazole + fluopyram is a new binary mixture fungicide product that is widely used to control many plant fungal pathogens and nematodes in several agricultural crops worldwide, including Egypt. However, there is a lack of information about their toxicological effects on honeybees (Apis mellifera L.). In the current study, the lethal and sub-lethal toxic effects of mixture tebuconazole + fluopyram were examined on A. mellifera workers. Tebuconazole + fluopyram exhibited low acute toxicity to A. mellifera foragers (the 96-h LC50 value was 1.389 mg a.i. · ml^–1). Sub-lethal effects of tebuconazole + fluopyram on survival, body weight, food consumption and antioxidant defenses of A. mellifera were determined by chronic oral exposure of A. mellifera workers to sugar syrup which contained two sublethal concentrations of the fungicide, 0.139 mg · ml^–1 (1/10 of 96 h LC50) and 0.278 mg · ml^–1 (1/5 of 96 h LC50), along with clear sugar syrup as a control for 18 days. Honeybees exposed to both sublethal concentrations of tebuconazole + fluopyram showed a significant decrease in the bees’ survivability and dry body weight. Sugar syrup and pollen consumption by the exposed A. mellifera were relatively less than by the controls. Tebuconazole + fluopyram also induced disruptions in the enzymatic antioxidant and detoxification defense systems in bees, indicating the presence of oxidative stress. Fungicide exposure elicited a significant depletion in catalase and superoxide dismutase activities and a significant elevation in glutathione and malondialdehyde levels in bees, indicating lipid peroxidation. This is the first study indicating the harmful impacts of tebuconazole + fluopyram on honeybee health.

The predatory efficacy of tilapia Oreochromis niloticus was confirmed against the immature stages of mosquitoes including Culex pipiens. The present study evaluated the detrimental impacts of sublethal concentration of myclobutanil (1000 µg/L) and S-metolachlor (140 µg/L) pesticides for 15 days on the predatory potential of O. niloticus on larvae of Cx. pipiens. Also, effects of both pesticides on acetylcholinesterase (AChE), and certain antioxidant parameters (i.e., total antioxidant capacity [TAC] and superoxide dismutase [SOD]) in the fish were assessed. The exposure of O. niloticus to sublethal concentration of myclobutanil and S-metolachlor caused destructive effects on the predatory behavior of the fish and decreased its predation rates on mosquito larvae compared to the control. Changes in predation capacity of the predatory fish on mosquito larvae may be due to the toxic effect of these pesticides on fish’s antioxidants and AChE activity. The fish pre-exposed to both pesticides presented a significant decrease in the TAC and a significant increase in the SOD activity relative to control group, indicating the advancement of oxidative stress in the treated fish. Fishes pre-exposed to sublethal of both pesticides also showed a significant increase in AChE activity. This study suggests a threat of S-metolachlor and myclobutanil to O. niloticus health and potential as a successful indigenous predatory fish on Cx. pipiens larvae.

The current study investigated the toxicity of five insecticides, indoxacarb,
thiamethoxam+chlorantraniliprole, chlorantraniliprole, fipronil and lufenuron against
the 2 nd and the 4 th instar larvae of the cotton leafworm, Spodoptera littoralis using leaf-
dip bioassay under laboratory conditions. Based on the LC 50s values of the tested
insecticides for the 2 nd instar larvae of S. littoralis, the most toxic insecticide was
indoxacarb (0.009, 0.006 and 0.001 ppm), followed by thiamethoxam +
chlorantraniliprole (0.016, 0.01 and 0.009 ppm fold), chlorantraniliprole (0.21, 0.12 and
0.052 ppm fold), fipronil (3.79, 2.81 and 0.661 ppm fold) and lufenuron (5.19, 3.21 and
0.916 ppm fold) after 24, 48 and 72 hrs. post exposure, respectively. The toxicity index
and relative potency values showed indoxacarb was more toxic for the 2nd instar larvae
than thiamethoxam + chlorantraniliprole, chlorantraniliprole, fipronil and lufenuron by
(1.78, 23.33, 421.11 and 576.67), (1.67, 20.00, 468.33 and 535.0) and (9.0, 52.0, 661.0
and 916.0) fold, respectively. The 4 th instar larvae showed high susceptibility to
indoxacarb compared thiamethoxam + chlorantraniliprole, chlorantraniliprole, fipronil
and lufenuron. The LC 50s values of the tested insecticides revealed that indoxacarb was
more effective than other insecticides (0.83, 0.61 and 0.32 ppm), followed by
thiamethoxam + chlorantraniliprole (7.11, 5.23 and 1.11 ppm), fipronil (10.11, 9.13 and
3.26 ppm) and lufenuron (16.38, 14.39 and 4.11 ppm) after 24, 48 and 72 hrs. exposure,
respectively. Therefore, our study recommended using indoxacarb, thiamethoxam +
chlorantraniliprole and chlorantraniliprole in controlling CLW because of their mode of
action are different and promising for using these insecticides in Integrated Pest
Management programs.

The German cockroach, Blattella germanica, is a prominent housing urban pest
that poses significant public health concerns due to its capacity to transmit various
pathogens. This study investigated the toxicity of several insecticides emamectin
benzoate, spinetoram, indoxacarb, thiocyclam hydrogen oxalate, and metaflumizone
alone and in combination with jojoba oil at concentrations of 250, 500, and 1000 ppm.
Based on the LC50s values of the tested insecticides for the adult of B. germanica, the
most toxic insecticide was emamectin benzoate (0.414, 0.012 and 0.002 ppm), followed
by spinetoram (2.96, 0.093 and 0.056 ppm), indoxacarb (4.88, 0.602 and 0.090 ppm),
thiocyclam hydrogen oxalate (17.04, 0.769 and 0.182 ppm), metaflumizone (96.67,
21.22 and 2.042 ppm) and jojoba oil (350.64, 258.97 and 197.61 ppm) after 24, 48 and
72 hrs. post exposure, respectively. The incorporation of jojoba oil as a synergist
significantly enhanced the toxicity, with pronounced effects observed at higher
concentrations and extended exposure durations. Emamectin benzoate, spinetoram and
indoxacarb showed marked improvements in efficacy when combined with jojoba oil.
In contrast, thiocyclam hydrogen oxalate and metaflumizone remained the least
effective compound, although slight enhancements were observed with jojoba
supplementation. These findings suggest that jojoba oil may function as a valuable
synergist, amplifying the insecticidal potency of conventional chemical agents. Its
integration into pest management programs could improve control outcomes for B.
germanica while potentially reducing the reliance on higher pesticide doses. Future
research should focus on practical, application-oriented strategies to establish jojoba as
a bioinsecticide and explore its combinations with other insecticides.