Cold weather reduces reproduction and demand for tomato plants in Tuta absoluta

Stress from low temperatures reduced emergence, fecundity, egg hatching, and orientation of females of Tuta absoluta (currently named Phthorimaea absoluta) for tomato plants. The effect increased with the intensity of the cold. The response involved physiological, biochemical, metabolic, and transcriptional changes in adult pests (DOI 10.3390/insects17070706).

A study conducted by Chinese researchers evaluated adult Tuta absoluta kept under three temperature regimes. The control remained at twenty-five degrees Celsius. Moderate cold stress occurred at fifteen degrees Celsius. Severe cold stress occurred at five degrees Celsius. The insects remained under a photoperiod of sixteen hours of light and eight hours of darkness. Biochemical, metabolomic, and transcriptomic analyses were performed using adults kept for seven days under these treatments.

Low temperatures impaired adult emergence. Control and moderate stress maintained the highest rates. Severe stress caused the greatest reduction. The result indicates impaired completion of metamorphosis after exposure to cold.

Greater impact

Reproduction was most impacted. Control females produced more eggs. Females under fifteen degrees Celsius showed a slight reduction, with no significant difference compared to the control. Females under five degrees Celsius had almost complete suppression of oviposition. Egg laying in the control and moderate treatment groups peaked on the seventh day. Then, it decreased on the fourteenth day and almost ceased on the twenty-first day. In severe cold, egg laying remained minimal throughout the period.

Egg hatching also decreased with increased stress. The control group showed greater hatching success. The treatment at fifteen degrees Celsius did not differ from the control. The treatment at five degrees Celsius caused the greatest reduction. Severe cold also delayed the hatching process.

Search for a host

Host-seeking behavior changed. Control females showed a clear preference for tomato odors in a Y-shaped olfactometer. Females subjected to fifteen degrees Celsius had less attraction to the plant. Females subjected to five degrees Celsius showed the lowest response to volatiles. The data indicate a progressive loss of the ability to locate the host mediated by smell.

Energy metabolism

Cold weather also altered energy metabolism. Triglyceride levels remained similar between the control group and moderate cold, but decreased in severe cold. Sodium-potassium ATPase activity followed a similar pattern. It remained stable below fifteen degrees Celsius and decreased below five degrees Celsius. This enzyme functions as an indicator of membrane ion transport. The decrease suggests impairment in bioenergetic processes associated with cellular homeostasis.

Glycogen reserves also decreased under severe cold. The content remained similar between control and moderate cold. The result indicates the use or loss of lipid and carbohydrate reserves under intense thermal stress. Trehalose showed a tendency to increase with decreasing temperature, but without statistical difference. This pattern suggests a possible metabolic adjustment associated with protection against cold.

Antioxidant enzymes responded differently. Superoxide dismutase activity increased under severe cold compared to the control. Peroxidase activity decreased below five degrees Celsius. Catalase activity did not change between treatments. This suggests a progressive alteration in defenses against oxidative stress.

Non-targeted metabolomics revealed widespread metabolic reprogramming. Control, moderate cold, and severe cold samples showed distinct metabolic profiles. Comparison between control and 15 degrees Celsius identified 324 reduced and 291 increased metabolites. Comparison between control and 5 degrees Celsius identified 297 reduced and 333 increased metabolites. Comparison between 5 and 15 degrees Celsius showed 111 reduced and 132 increased metabolites.

The affected pathways included amino acid metabolism, alkaloid biosynthesis, central carbon metabolism, transfer aminoacyl-RNA biosynthesis, tyrosine metabolism, purine metabolism, alanine, aspartate and glutamate metabolism, arginine biosynthesis, nicotinate and nicotinamide metabolism, phenylalanine metabolism, terpenoid and steroid biosynthesis, and carbon metabolism.

Transcriptomic analysis

Transcriptomic analysis also showed a clear separation between treatments. The comparison between control and moderate cold showed the greatest alteration: nine hundred and thirty-nine genes with lower expression and one hundred and four with higher expression. The comparison between control and severe cold indicated eighty-four genes with lower expression and fifty-eight with higher expression. The comparison between the two levels of cold showed one hundred and thirty-seven reduced genes and one hundred and forty-five increased genes.

The enriched gene pathways involved thermogenesis, oxidative phosphorylation, MAPK signaling, glycolysis, gluconeogenesis, propanoate metabolism, cGMP-PKG signaling, and processes associated with cellular response, metabolism, biological regulation, development, and response to stimuli. The study also found coordinated networks between genes and metabolites. These networks grew in proportion to the intensity of the stress.

Researchers conclude that adult Tuta absoluta triggers an integrated response to cold. The pest prioritizes survival mechanisms, with changes in energy metabolism, accumulation of cryoprotectants, and antioxidant defenses. In parallel, it reduces reproduction, growth, and host searching. The results help explain the species' response to low temperatures and may support population dynamics models and management strategies under variable climate scenarios.