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Survival and mortality of females and males of Oligonychus punicae (Trombidiformes: Tetranychidae) on three host plants under laboratory conditions

Under laboratory conditions, *Oligonychus punicae* mites exhibited significantly greater longevity and slower mortality rates on avocado leaves compared to rose and guamuchil, with males consistently outliving females across all host plants, suggesting that avocado is the most suitable host while the observed sex-specific survival differences highlight a clear instance of sexual conflict.

Original authors: Yahir Alejandro Guevara-Gamez, Julio César Chacón-Hernández, Salvador Ordaz-Silva, Rafael Delgado-Martínez, Imelda Virginia López-Sánchez, Mario Rocandio-Rodríguez, Sandra Grisell Mora-Ravelo, Jorge L

Published 2026-09-18

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CC BY 4.0

Original authors: Yahir Alejandro Guevara-Gamez, Julio César Chacón-Hernández, Salvador Ordaz-Silva, Rafael Delgado-Martínez, Imelda Virginia López-Sánchez, Mario Rocandio-Rodríguez, Sandra Grisell Mora-Ravelo, Jorge Luis Delgadillo-Ángeles

Original paper licensed under CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). ⚕️ This is an AI-generated explanation of a preprint that has not been peer-reviewed. It is not medical advice. Do not make health decisions based on this content. Read full disclaimer

In the hidden world of microscopic life, the way an organism ages and dies tells a story about its environment, its biology, and its relationships with others. Scientists who study these patterns look at survival curves, which are essentially maps showing how long a population lives under specific conditions. These maps reveal whether a creature dies young and often, or if it survives for a long time before facing a sudden increase in death rates. Understanding these patterns is vital for managing pests that damage crops, as it helps researchers predict how quickly a population might grow or collapse. When a pest feeds on different plants, its life span can change dramatically, offering clues about which plants are good hosts and which are hostile. This knowledge is the foundation for developing control methods that rely on natural biology rather than just chemical sprays, a crucial step in protecting the global food supply.

In a recent study, researchers set out to examine the life and death of a specific pest known as the avocado brown mite. This tiny arachnid is a major problem for avocado farmers in Mexico, but it also feeds on other plants, including roses and a tree called guamuchil. The scientists wanted to know how long these mites lived and how quickly they died when placed on leaves from these three different plants. They also sought to understand if there was a difference in how long the males and females lived, a detail that had been largely overlooked in previous research. To do this, they brought the mites into a laboratory setting, placing pairs of males and females on small squares of leaves from avocado, rose, and guamuchil trees. They watched these pairs every day, recording who survived and who died, until the last mite had passed away.

The results painted a clear picture of how the host plant influences the mites' lives. On the avocado leaves, both male and female mites lived the longest. The females survived for about 35 days, while the males lived even longer, reaching 44 days. In contrast, on the leaves of the rose and guamuchil trees, the mites did not last as long. Females on these plants lived for only 31 days, and males lived for 37 days. The data showed that the avocado was the most suitable home for these mites, allowing them to age more slowly and live longer than they did on the other two plants. The researchers found that the mites on the rose and guamuchil leaves faced a faster increase in their risk of dying as they got older, suggesting that these plants are not ideal environments for the pest.

A striking discovery was that in every case, the male mites lived longer than the females. This difference was consistent across all three types of plants. The study suggests that this gap in longevity is not just about the food they ate, but also about how they interact with each other. The researchers propose that the constant pressure of mating and the energy females spend on producing eggs take a heavy toll on their bodies. While the males invest energy in finding mates and producing sperm, the females seem to pay a higher price in terms of their own survival. The study indicates that the social interactions between the sexes, particularly the behavior of the males, may actually shorten the lives of the females.

The researchers also looked at how the risk of death changed as the mites aged. They found that for both sexes on all three plants, the risk of dying increased as they got older, a pattern known as a Type I survival curve. This means that the mites were likely to survive their early and middle years, only to face a sharp rise in mortality as they reached old age. However, the speed at which this risk doubled was faster on the rose and guamuchil leaves than on the avocado leaves. This means that the mites on the non-avocado plants aged more rapidly, facing a quicker decline in their health. The study concludes that while the avocado is a comfortable home that supports a long life, the rose and guamuchil are less suitable, causing the mites to age faster and die sooner. These findings provide a deeper understanding of the avocado brown mite's biology, highlighting that the plant it feeds on and its interactions with the opposite sex are key factors in determining how long it will live.

Technical Summary: Survival and Mortality of Oligonychus punicae on Three Host Plants

Problem Statement
The avocado brown mite, Oligonychus punicae (Trombidiformes: Tetranychidae), is a significant pest of avocado (Persea americana) crops in Mexico, which is the world's leading producer of the fruit. While chemical control is common, the mite's rapid generation time and growth rate increase the risk of pesticide resistance, necessitating a deeper ecological understanding for integrated management. Previous research, such as that by González-Hernández (2024), has documented the survival of immature stages and female longevity on various hosts but has left critical gaps regarding male longevity, sex-specific mortality rates, mortality doubling times, and the specific types of survival curves for adult males and females across different host plants. Furthermore, the influence of host plant species on the senescence patterns and sexual interactions affecting survival remains insufficiently characterized.

Methodology
The study was conducted under laboratory conditions at the Universidad Autónoma de Tamaulipas. Adult O. punicae were collected from Pithecellobium dulce (guamuchil) in Ciudad Victoria and reared on bean plants (Phaseolus vulgaris) for three generations. The experimental design utilized leaf squares (4 cm²) from three host plants: avocado (cultivar Hass), guamuchil, and rose (Rosa hybrida).

Thirty pairs of adult mites (one male and one female per pair) were placed on leaf squares for each host species. Due to accidental mortality (drowning in cotton), the final analysis was based on 25 pairs per host. Mites were transferred to fresh, sterilized leaf squares every three days to maintain nutritional quality. Daily monitoring recorded survivorship ( $l_x$ ), survival period ( $p_x$ ), mortality frequency ( $d_x$ ), and additional life expectancy ( $e_x$ ).

Data analysis employed the Weibull distribution to model survival curves and distinguish curve types (Type I, II, or III) based on the shape parameter ( $c$ ). The Gompertz mortality model was used to estimate the instantaneous mortality rate ( $\mu_x$ ) and the mortality rate doubling time (DT). Entropy ( $H$ ) was calculated to measure the heterogeneity of the mortality distribution. Statistical comparisons included the log-rank test for survival distributions and confidence interval overlap analysis for model parameters.

Key Results

Survival Curves: Both sexes exhibited a Type I survival curve (where mortality risk increases with age, $c > 1$ ) on all three host plants. The Weibull model provided a strong fit for the data (Pseudo- $R^2$ values ranging from 0.97 to 0.99).
Host Plant Influence: Longevity was significantly greater on avocado leaves compared to guamuchil and rose for both sexes.
- Females: Mean longevity was 23.60 days on avocado, versus 20.25 days on guamuchil and 20.29 days on rose. Maximum observed survival reached 35 days on avocado and 31 days on the other hosts.
- Males: Mean longevity was 28.31 days on avocado, versus 24.58 days on guamuchil and 24.9 days on rose. Maximum observed survival reached 44 days on avocado and 37 days on the other hosts.
- Statistical analysis confirmed significant differences in survival distributions between avocado and the other two hosts, but no significant difference was found between guamuchil and rose.
Sexual Dimorphism: Males consistently outlived females across all host plants. The study observed that females began to decline in survival earlier (day 14 on avocado; day 11 on others) compared to males (day 17 on avocado; day 16 on others).
Mortality Dynamics: The Gompertz model indicated that the logarithm of the instantaneous mortality rate increased linearly with age. The mortality rate doubling time (DT) was shorter for both sexes on guamuchil and rose compared to avocado, indicating a faster acceleration of mortality on the non-avocado hosts. Specifically, female DT was shorter than male DT across all hosts.
Entropy: Entropy values ( $H$ ) ranged from 0.2350 to 0.2947, indicating a convex survival timeline where small changes in mortality rates significantly impact life expectancy.

Key Contributions
This research provides the first comprehensive demographic data for adult male O. punicae alongside females across three distinct host plants. It quantifies the mortality doubling time and characterizes the specific type of survival curve (Type I) for this pest, filling a gap left by previous studies that focused primarily on females or immature stages. The study establishes that P. dulce and R. hybrida are unsuitable hosts for adult O. punicae compared to P. americana, as evidenced by reduced longevity and accelerated mortality rates.

Significance and Claims
The authors claim that the observed patterns highlight a clear instance of sexual conflict in O. punicae, where male harassment or mating interactions drastically reduce female fitness and survival. The study posits that the greater energy expenditure by females for egg production, combined with the costs of interacting with males, leads to higher mortality rates and shorter lifespans compared to males.

The findings suggest that host plant selection is a critical factor in the population dynamics of O. punicae. The authors conclude that understanding these sex-specific survival dynamics and the impact of intersexual interactions is essential for accurately interpreting the demographic response of the mite. This information serves as a basis for selecting appropriate experimental hosts and refining management strategies, noting that while laboratory results are clear, field interactions involving population density and resource availability may introduce further complexity. The paper does not propose specific new control methods but emphasizes the need for further research into virgin vs. mated mite comparisons and the potential role of males in female dispersal.

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