# Effects of different diets on life table parameters of the predatory mite Phytoseius plumifer (Acari: Phytosiidae)

Mahmoud M Al-Azzazy, Saleh S Alhewairini

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Mahmoud M Al-Azzazy, Saleh S Alhewairini. Effects of different diets on life table parameters of the predatory mite Phytoseius plumifer (Acari: Phytosiidae). Acarologia, 2024, 64 (4), pp.1019-1029. 10.24349/hwu2-v0ct. hal-04735181

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# Effects of different diets on life table parameters of the predatory mite *Phytoseius plumifer* (Acari: Phytoseiidae)

Mahmoud M. Al-Azzazy IDª, Saleh S. Alhewairini IDª

## Original research

### ABSTRACT

The predatory mite *Phytoseius plumifer* (Canestrini & Fanzago) (Acari: Phytoseiidae) is an effective predator of phytophagous mites in several countries worldwide. Plant pollen is an important alternative food for generalist predatory mites, ensuring survival and fostering population growth during periods of prey scarcity. The objective of this study was to compare the effects of a diet of a natural prey, *Oligonychus afrasiaticus* (McGregor 1939) (Acari: Tetranychidae), and a diet of pollens, e.g. corn pollen or date palm pollen, on *P. plumifer* life table parameters under laboratory conditions. The total developmental time was significantly shorter for *P. plumifer* females fed on *O. afrasiaticus* than corn or date palm pollen. However, diet type did not affect *P. plumifer* survival rate. Survivorship during immature development varied from 96 to 99% on the three tested diets. Adult females that fed on *O. afrasiaticus* lived longer, produced more eggs, and had longer oviposition periods. The highest mean of daily oviposition of *P. plumifer* was recorded when predator was fed on *O. afrasiaticus* 2.26 eggs/♀/day, while the lowest mean of daily oviposition was recorded when predator was fed with corn pollen 1.53 eggs/♀/day. The average number of preys consumed daily by the protonymphs, deutonymphs and adult female individuals was 8.09, 11.20 and 18.18, respectively. Throughout the whole life-span *P. plumifer* female fed on an average of 739.26 prey, of these more than 96% were consumed during the adult stage. The highest intrinsic rate of increase ($r_m$), net reproduction rate ($R_o$) and finite rate of increase ($\lambda$) were recorded when predator fed on *O. afrasiaticus*. Mean generation time (T) was shorter for *P. plumifer* fed on *O. afrasiaticus* than date palm pollen or corn pollen. Based on the findings, in the scarcity or absence of the main prey in the environment, the date palm pollen or corn pollen can be suggested as an alternative or supplementary food for *P. plumifer*. Also, the predatory mite, *P. plumifer* has good potential to suppress *O. afrasiaticus* populations and can be used in the biological control strategies against this pest.

**Keywords** biological control; life table parameters; alternative food; date palm

### Introduction

The predatory mite *Phytoseius plumifer* (Canestrini & Fanzago) (Acari: Phytoseiidae) is a type III generalist predator (McMurtry *et al.* 2013). It has a wide diet range including tetranychid (Kouhjani-Gorji *et al.* 2008), eriophyid (Louni *et al.* 2014), tarsonemid mites (Fouly *et al.* 2019), and plant pollen (Khodayari *et al.* 2013). The date palm mite, *Oligonychus afrasiaticus* (McGregor) (Acari: Tetranychidae), is a severe pest of the date fruit in the Middle Eastern countries (Palevsky *et al.* 2004), arid regions (Hussain 1974), and in most of the Northern

Received 17 February 2024
Accepted 30 September 2024
Published 04 October 2024

Corresponding author
Mahmoud M. Al-Azzazy ID:
m.elazzazy@qu.edu.sa

Academic editor
Tsolakis, Haralabos

https://doi.org/10.24349/hwu2-v0ct

ISSN 0044-586X (print)
ISSN 2107-7207 (electronic)

<figure><img src="image_2.png" /></figure>

Al-Azzazy M. M. and Alhewairini S. S.

Licensed under
Creative Commons CC-BY 4.0

<footnote>ªDepartment of Plant Protection, College of Agriculture and Food, Qassim University, P.O. Box 6622, Buraidah 51452, Qassim, Saudi Arabia.</footnote>
Africa (Zaher *et al.* 1982; Ben Chaaban *et al.* 2011). In Saudi Arabia, *O. afrasiaticus* is also one of the primary pests of date palms. When it exists, fruits may sustain serious damage (Talhouk, 1991; Ben Chaaban *et al.* 2011). The activity of *O. afrasiaticus* begins and peaks through the unripe, Kimri stage characterized by high acidic, moisture contents and low sugar (Palevsky *et al.* 2005).

Currently, management practices of pests are generally limited to chemical pesticide application, and date palm orchards are submitted to very high levels of synthetic pesticides (Al-Dosary 2010). In addition to having detrimental effects on biodiversity, the use of synthetic pesticides to control phytophagous mites led to death of non-target organisms, the presence of residues in crops, and the development of mite resistance (Desneux *et al.* 2007; Guedes *et al.* 2016; Ziad 2017; Lorenzon *et al.* 2018; Malagnini *et al.* 2023). These side effects strongly limit the agricultural systems' sustainability and primarily necessitate the development of non-chemical techniques of pest control (Khan *et al.* 2023). Consequently, it is imperative to find effective biocontrol agents against *O. afrasiaticus*.

Generalist predatory mites can exploit various food sources, including natural prey and plant pollen (Xin and Zhang 2021; Shishehbor *et al.* 2022). Additionally, plant pollens are suitable as an alternative or additional food sources with high nutritional value for some predatory mites (McMurtry *et al.* 2013; Xin and Zhang 2021; Coll and Guershon 2022).

Several phytoseiid species rely on pollen to reach their maximum reproductive capacity (McMurtry *et al.* 2013; Barzkar *et al.* 2023). Several studies demonstrated that a source of pollen into a crop can boost the biological control due the improvement in reproduction and survival of predatory mites (Duarte *et al.* 2015; Vacacela *et al.* 2019; Van Rijn *et al.* 2022; Lamlom *et al.* 2024). For example, date palm pollen, *Phoenix dactylifera* L., castor-oil pollen, *Ricinus communis* L., and corn pollen, *Zea mays* L. are potential plant pollen diets for rearing *P. plumifer* (Zaher *et al.* 1969; Rasmy and El-Banhawy 1974; Khodayari *et al.* 2013). Although biological characteristics of *P. plumifer* fed on eriophyid (Rasmy and El-Banhawy 1974; Louni *et al.* 2014; Al-Azzazy and Alhewairini 2020), tetranychid (Zaher *et al.* 1969; Rasmy and El-Banhawy 1974; Kouhjani-Gorji *et al.* 2008; Shakarami and Bazgir 2017) and tarsonemid mite species (Fouly *et al.* 2019) have been studied previously, no information is available on *P. plumifer* attacking or feeding on *O. afrasiaticus* in Saudi Arabia or elsewhere.

Therefore, our purpose in the present study was to develop a comprehensive understanding of the comparison of natural prey *O. afrasiaticus*, corn pollen and date palm pollen diets, on the developmental times, survival, reproduction rate, and life table parameters of the predator *P. plumifer*. These data are necessary to understand and predict the performance of this natural enemy under field conditions.

# Material and methods

## Pollen collection

Fresh date palm pollen *P. dactylifera* var. Barhi was collected from date trees planted in the Qassim region, Saudi Arabia. Pollens were oven-dried at 26 °C for one day and then stored at -17 °C. The corn pollen, *Z. mays* was purchased from a rural supplier in Qassim city. Pollen was stored in a freezer at -5 °C for up to 2 weeks before experimentation.

## Mite colonies

Predatory mite, *P. plumifer* was originally collected from unsprayed short heighted medium-laden date palm Barhi variety located in the Agricultural Experiments Station, Qassim University, Al-Mulida district (26.297875° N, 43.790684° E), Saudi Arabia. Individuals of *O. afrasiaticus* were collected from severely infested date palm trees in the same orchard. Predatory mite colonies were kept apart in rearing arenas constructed from kidney bean *Phaseolus vulgaris* L. (Fabaceae) leaves which were submerged in water-soaked cotton within
plastic trays measuring 10 x 15 cm in length and 2 cm in height. The incubator was set to 32 °C, 50% RH, and 12L:12D photoperiod.

To preserve leaf freshness and a steady water level, water was fed to the plastic trays daily. To prevent mites from escaping, strips of moist tissue paper were placed around the margins of the bean leaves. Moreover, every 5 days, the predators were transferred to new rearing arenas. The predatory mite was fed with different stages of *O. afrasiaticus*. Before the trials started, the *P. plumifer* colony was reared for numerous generations feeding on *O. afrasiaticus*.

## Experimental units

To obtain individuals with the same age for experiments, one hundred and sixty adult females from the stock colony were moved to a different arena. The females were allowed to oviposit for one day and all adults were then removed from the leaf discs. The freshly molted larvae were separately placed in rearing arenas consisting of bean leaf discs using a hairbrush.

Sample sizes for *P. plumifer* development, survival, reproduction, and life table parameters tests were 60 individuals in *O. afrasiaticus*, 50 in corn pollen, and 44 in date palm pollen treatments. The bean leaf discs including the midrib (2.0 cm in diameter) were placed upside down on a moistened layer of cotton (2 mm thick) in a Pyrex® Petri dish (5 cm in diameter × 2.5 cm high), following Al-Azzazy and Alhewairini (2020) methodology. Distilled water was added to every rearing arena daily, to maintain a constant water level. The mites were moved to newly cut discs as the leaf discs grew older.

## Immature development, reproduction and predation rate

The development, survival rate, reproduction, sex ratio, fecundity, longevity, and life table parameters of *P. plumifer* were determined by feeding it with one of the following food sources: (1) *O. afrasiaticus*, (2) date palm pollen, and (3) corn pollen. In the prey treatment, the freshly molted larvae were fed on a mixture of 15 prey of different nymphal stages (protonymphs and deutonymphs) of *O. afrasiaticus* while each adult predator was fed on 25 individuals. Predation rate was recorded as the quantity of prey that was consumed. To ensure a plentiful food supply, everyday prey that was consumed was replaced by alive ones from the stock colony.

The experimental units were recorded daily at 12h intervals to record the developmental duration and survival rate of immature stages. Molting was verified by the existence of exuviae in the rearing arenas. After the adult female emerged in each treatment, a single male was placed to allow mating. To ensure multiple mating, the couple was maintained together up to the end of the experiments. The rearing arenas were monitored daily and pre-oviposition period, oviposition period, post-oviposition period, adult longevity, total fecundity, and mortality were recorded.

To distinguish predation rate of females from males, the predation rate of thirty males was evaluated under same conditions. Then, the mean of predation rate of male was subtracted from the average predation rate of the couples following Moghadasi *et al.* (2006).

## Sex ratio

Thirty eggs were individually moved to a new arena to evaluate the predator's sex ratio. The hatched larvae were raised until they reached adulthood, at which point their sex was determined. In the pollen treatments, about 10 mg of corn or date palm pollen was added to respective treatment dishes. New pollen replaced the old every other day.

## Statistical analysis

Developmental time, survival rate, pre-, post- and oviposition periods, longevity, and fecundity of *P. plumifer* fed *O. afrasiaticus*, corn and date palm pollen were analyzed using a one-way analysis of variance (one-way ANOVA). Tukey's Honestly Significant Difference (HSD) test
<table><caption>**Table 1** Mean (± SE) immature development time days of *Phytoseius plumifer* feeding on different diets.</caption><thead><tr><th rowspan="2">Parameters</th><th rowspan="2">Sex</th><th colspan="3">Natural prey and pollen diets</th></tr><tr><th><i>O. afrasiaticus</i> (n = 60)</th><th>Date palm pollen (n = 50)</th><th>Corn pollen (n = 44)</th></tr></thead><tbody><tr><td rowspan="2">Egg incubation period</td><td>Female</td><td>2.08 ± 0.06 a*</td><td>2.10 ± 0.12 a</td><td>2.00 ± 0.10 a</td></tr><tr><td>Male</td><td>2.00 ± 0.08 a</td><td>2.05 ± 0.10 a</td><td>2.00 ± 0.12 a</td></tr><tr><td rowspan="2">Larva</td><td>Female</td><td>1.00 ± 0.06 a</td><td>1.10 ± 0.11 a</td><td>1.05 ± 0.09 a</td></tr><tr><td>Male</td><td>1.00 ± 0.10 a</td><td>1.10 ± 0.09 a</td><td>1.07 ± 0.10 a</td></tr><tr><td rowspan="2">Protonymph</td><td>Female</td><td>1.05 ± 0.04 a</td><td>2.00 ± 0.18 b</td><td>2.04 ± 0.14 b</td></tr><tr><td>Male</td><td>1.00 ± 0.11 a</td><td>1.98 ± 0.06 b</td><td>2.00 ± 0.16 b</td></tr><tr><td rowspan="2">Deutonymph</td><td>Female</td><td>1.22 ± 0.12 a</td><td>1.63 ± 0.16 b</td><td>1.87 ± 0.20 c</td></tr><tr><td>Male</td><td>1.20 ± 0.10 a</td><td>1.59 ± 0.09 b</td><td>1.82 ± 0.13 c</td></tr><tr><td rowspan="2">Total</td><td>Female</td><td>5.35 ± 0.20 a</td><td>6.83 ± 0.24 b</td><td>6.96 ± 0.24 b</td></tr><tr><td>Male</td><td>5.20 ± 0.16 a</td><td>6.72 ± 0.20 b</td><td>6.89 ± 0.28 b</td></tr></tbody></table>

was used to separate the means at $\alpha = 0.05$. The statistical program SPSS version 22 (SPSS for Windows, SPSS Institute Inc., Chicago, IL, USA) was utilized for data analysis.

Life table parameters, i.e., net reproductive rate ($R_0$), intrinsic rate of increase ($r_m$), finite rate of increase ($\lambda$), gross reproductive rate (GRR), and mean generation time (T) were calculated with the TWOSEX-MSChart program (Chi 2024). The population doubling time (DT) of *P. plumifer* was also estimated using the formula $DT = \ln(2)/rm$, which indicates the number of days needed for the population to double in numbers. The population growth parameters' standard error (SE) was calculated according to (Maia et al. 2000).

# Results

## Developmental time, survival of immature stages and sex ratio

*Phytoseius plumifer* reached adult stage, and successfully preyed on *O. afrasiaticus*. The developmental time of *P. plumifer* on the tested diets are shown in (Tables 1 and 2). The results demonstrated that 100% of the eggs hatched. Total developmental time of *P. plumifer* males and females were affected significantly by diet type (females: $F = 36.42$; $df = 2, 81$; $P < 0.001$; males: $F = 5.72$; $df = 2, 28$; $P = 0.004$). The development time was significantly shorter for females and males fed on *O. afrasiaticus* than palm pollen or corn pollen (Tables 1 and 2). Survival rate during the immature stages of development exceeded 96% on the three tested diets (Table 3). The percentage survival rate of females and males was not significantly impacted by

<table><caption>**Table 2** Mean (± SE) pre-oviposition, oviposition, post-oviposition, longevity, and life span (days) of *Phytoseius plumifer* fed different diets at 32 ± 1 °C, 50% ± 5% RH.</caption><thead><tr><th rowspan="2">Parameters</th><th colspan="3">Natural prey and pollen diets</th></tr><tr><th><i>O. afrasiaticus</i></th><th>Date palm pollen</th><th>Corn pollen</th></tr></thead><tbody><tr><td>Adult preoviposition period (APOP)</td><td>2.15 ± 0.26 a</td><td>3.86 ± 0.31 b</td><td>4.02 ± 0.18 b</td></tr><tr><td>Oviposition period (OP)</td><td>28.40 ± 1.57 a</td><td>19.81 ± 1.95 b</td><td>18.66 ± 1.42 b</td></tr><tr><td>Total preoviposition period (TPOP)</td><td>30.55 ± 2.11 a</td><td>23.67 ± 1.86 b</td><td>22.67 ± 2.15 a</td></tr><tr><td>Post-oviposition period</td><td>8.89 ± 0.84 a</td><td>9.14 ± 0.38 a</td><td>9.72 ± 0.45 a</td></tr><tr><td>Female longevity</td><td>39.44 ± 2.15 a</td><td>32.81 ± 1.94 b</td><td>32.40 ± 2.31 b</td></tr><tr><td>Male longevity</td><td>36.71 ± 1.88 a</td><td>32.25 ± 1.70 b</td><td>30.55 ± 2.07 b</td></tr><tr><td>Female life span</td><td>44.79 ± 2.56 a</td><td>39.64 ± 2.80 b</td><td>39.36 ± 1.72 b</td></tr><tr><td>Male life span</td><td>41.91 ± 2.10 a</td><td>38.97 ± 1.88 b</td><td>37.44 ± 2.04 b</td></tr></tbody></table>

<footnote>*The same letters in rows denote not significantly different, using the Tukey test at 5% significance level. n = number of mites reaching adulthood.</footnote>

<footnote>The same letters in rows denote not significantly different, using the Tukey test at 5% significance level.</footnote>
<table><caption>**Table 3** Survival percentages of *Phytoseius plumifer* immature stages fed different diets at 32 ± 1 °C, 50% ± 5% RH.</caption><thead><tr><th rowspan="3">Diet</th><th colspan="4">Phytoseius plumifer</th><th rowspan="3">Survival to<br>adulthood (% ± SE)</th></tr><tr><th colspan="4">Stage specific survival (% ± SE)</th></tr><tr><th>Egg</th><th>Larva</th><th>Protonymph</th><th>Deutonymph</th></tr></thead><tbody><tr><td>O. afrasiaticus</td><td>100 ± 0.00 a</td><td>100 ± 0.00 a</td><td>100 ± 0.00 a</td><td>99.50 ± 0.06 a</td><td>99.00 ± 0.08 a</td></tr><tr><td>Date palm pollen</td><td>100 ± 0.00 a</td><td>100 ± 0.00 a</td><td>98.60 ± 1.08 a</td><td>98.20 ± 1.24 a</td><td>98.00 ± 1.12 a</td></tr><tr><td>Corn pollen</td><td>100 ± 0.00 a</td><td>98.40 ± 1.38 a</td><td>98.00 ± 1.46 a</td><td>97.10 ± 2.16 a</td><td>96.00 ± 3.28 a</td></tr></tbody></table>

Means followed by the same letter inside a column are not significantly different (Tukey HSD test; P<0.05)

the type of diet (F = 1.46; df = 2, 7; P = 0.31) which was 99.00 ± 0.08, 98.00 ± 1.12, and 96.00 ± 3.28 for *P. plumifer* fed on *O. afrasiaticus*, date palm pollen, and corn pollen, respectively.

Contrary, the food type had a discernible, noteworthy impact on the sex ratio. Sex ratio on all diets varied between 50 and 73.33%. A maximum female-biased sex ratio was observed by *P. plumifer* fed on *O. afrasiaticus* (Table 5). The female-to-male offspring ratio was about (2.2:1, 2:1 and 1.5:1), when predator fed on *O. afrasiaticus*, date palm pollen, and corn pollen, respectively. Although females developed slightly slower than males, there was no significant variation between the periods of development on the three tested diets.

## Reproduction

In general, no significant difference in the pre-oviposition period was observed between date palm pollen and corn pollen, while the shortest pre-oviposition period was recorded on *O. afrasiaticus*. The oviposition period was significantly different among diets (F = 31.56; df = 2, 86; P < 0.001). The longest overall oviposition duration was observed in case of feeding on *O. afrasiaticus*, whereas it was the shortest when the predators fed on corn pollen (Table 2).

Total fecundity was significantly affected by diet (F = 35.32; df = 2, 84; P < 0.001; Table 4). *Phytoseius plumifer* females fed on *O. afrasiaticus* exhibited a higher rate of fecundity than those feeding on date palm pollen or corn pollen. The highest number of eggs was recorded when *P. plumifer* fed on *O. afrasiaticus*, while the minimum was when *P. plumifer* fed on corn pollen. Therefore, it could be concluded that the date palm mite, *O. afrasiaticus* was suitable prey for *P. plumifer*. There was no difference in *P. plumifer* post-oviposition periods between the three diets that were examined. The diet had a clear significant effect on the longevity (F = 59.82; df = 2, 80; P < 0.001 for females; F = 20.34; df = 2, 75; P < 0.001 for males; Table 2). Compared to diets containing date palm pollen or corn pollen, *P. plumifer* males and females lived longer when fed the *O. afrasiaticus* diet.

## Predation rate

The larval stage of *P. plumifer* did not feed on the date palm mite, *O. afrasiaticus*, and predation began to occur just after the mites entered the protonymphal stage. During the immature stages, *P. plumifer* females consumed mean of 9.66 ± 0.95 *O. afrasiaticus* nymphal stages per

<table><caption>**Table 4** Fecundity of *Phytoseius plumifer* fed different diets at 32 ± 1 °C, 50% ± 5% RH.</caption><thead><tr><th rowspan="2">Diet</th><th colspan="2">Phytoseius plumifer</th></tr><tr><th>Total fecundity± SD</th><th>Daily fecundity</th></tr></thead><tbody><tr><td>O. afrasiaticus</td><td>64.42±1.65 a</td><td>2.26± 0.09</td></tr><tr><td>Date palm pollen</td><td>39.61± 1.49 b</td><td>1.99± 0.08</td></tr><tr><td>Corn pollen</td><td>28.73± 1.82 c</td><td>1.53± 0.11</td></tr></tbody></table>

Values followed by the different letters in the same column are significantly different, using the Tukey test at 5% significance level.
<table><caption>**Table 5** Predation rate of *Phytoseius plumifer* feeding on date palm mite, O. afrasiaticus at 32 ± 1 °C, 50% ± 5% RH.</caption><thead><tr><th rowspan="2">Predatory stage</th><th rowspan="2">Sex</th><th colspan="2">No. of attacked mite individuals</th></tr><tr><th>Total average mean ± SD</th><th>Daily rate, mean ± SD</th></tr></thead><tbody><tr><td rowspan="2">Protonymph</td><td>Female</td><td>8.50±0.10 a</td><td>8.09±0.20 a</td></tr><tr><td>Male</td><td>8.00±0.18 a</td><td>8.00±0.16 a</td></tr><tr><td rowspan="2">Deutonymph</td><td>Female</td><td>13.45±0.28 a</td><td>11.02±0.30 a</td></tr><tr><td>Male</td><td>12.00±0.32 a</td><td>10.00±0.36 a</td></tr><tr><td rowspan="2">Total</td><td>Female</td><td>21.95±1.14 a</td><td>9.66±0.95 b a</td></tr><tr><td>Male</td><td>20.00±1.06 a</td><td>9.00±0.80 a</td></tr><tr><td>Pre-oviposition</td><td>Female</td><td>32.94±2.28</td><td>15.32±1.56</td></tr><tr><td>Oviposition</td><td>Female</td><td>615.14±6.17</td><td>21.65±1.64</td></tr><tr><td>Post-oviposition</td><td>Female</td><td>69.23±2.42</td><td>7.78±1.12</td></tr><tr><td rowspan="2">Longevity</td><td>Female</td><td>717.31±7.90 a</td><td>18.18±1.25 a</td></tr><tr><td>Male</td><td>531.92±5.41 b</td><td>14.49±1.55 b</td></tr></tbody></table>

Values in columns followed by the same letter are not significantly different, using one-way ANOVA test: P<0.05.

day. The mean daily predation rate was significantly affected by predator age (*P* < 0.001), daily consumption increased significantly in adults. Predation rates increased throughout the pre-oviposition and oviposition periods and reduced during the post-oviposition period. Subsequently, daily predation decreased with age. Through the oviposition period, the female consumed an average of 21.65 ± 1.64 *O. afrasiaticus*, marking the greatest rate that was observed. The number of preys consumed during the longevity reported for *P. plumifer* females was 717.31 ± 7.90 prey, while for males, it was 531.92 ± 5.41 prey.

## Life-table parameters

Life table parameters proved that food type had significant impacts on *P. plumifer* life history (Table 6). The females reared on *O. afrasiaticus* showed the highest net reproductive rate (*R*<sub>o</sub>), intrinsic rate of natural increase (*r*<sub>m</sub>) and finite rate of increase (*λ*). On the other hand, *P. plumifer* individuals reared on *O. afrasiaticus* had the shortest mean generation time. Life table parameters were estimated as net reproduction rate (*R*<sub>o</sub>) of 28.72, 22.21, 18.44, mean generation time (T) of 14.16, 17.45, 22.67 d, the intrinsic rate of population increase (*r*<sub>m</sub>) 0.278, 0.241, 0.141 day<sup>-1</sup>, finite rate of increase (*λ*) of 1.34, 1.29, 1.19 for *P. plumifer* when fed on *O. afrasiaticus*, date palm pollen, and corn pollen respectively. Note that *P. plumifer* fed on corn pollen had the lowest values of life table parameters and the longest mean generation time.

<table><caption>**Table 6** Table 6 Effect of different diets on the life-table parameters of *Phytoseius plumifer* at 32 ± 1 °C, 50% ± 5% RH. The values are shown as means ± SE.</caption><thead><tr><th rowspan="2">Parameters</th><th colspan="3">Natural prey and pollen diets</th></tr><tr><th>O. afrasiaticus</th><th>Date palm pollen</th><th>Corn pollen</th></tr></thead><tbody><tr><td>Net reproduction rate (R<sub>o</sub>)</td><td>28.72±2.50 a</td><td>22.21±2.75 b</td><td>18.44±2.30 c</td></tr><tr><td>Mean generation time (T) (days)</td><td>14.16±0.22 a</td><td>17.45±0.88 b</td><td>22.67±1.10 c</td></tr><tr><td>Intrinsic rate of increase (r<sub>m</sub>) day<sup>-1</sup></td><td>0.278±0.01 a</td><td>0.241±0.01 b</td><td>0.141±0.02 c</td></tr><tr><td>Finite rate of increase (λ) day<sup>-1</sup></td><td>1.34±0.01 a</td><td>1.29±0.02 b</td><td>1.19±0.01 c</td></tr><tr><td>Sex ratio<br>(n = 30)</td><td>0.73<br>(f = 22; m = 8)</td><td>0.66<br>(f = 20; m = 10)</td><td>0.5<br>(f = 15; m = 15)</td></tr></tbody></table>
Discussion

It is the first time to assess the biology and predatory efficiency of *P. plumifer* against *O. afrasiaticus*. The current study demonstrates that *O. afrasiaticus* is a highly nutritious and suitable prey, leading to rapid development and a high rate of fecundity. The predatory mite was also able to develop and reproduce successfully when fed on date palm pollen or corn pollen. This is a significant step in developing management strategies against *O. afrasiaticus*.

In this study, the type of diet had a clear influence on *P. plumifers* immature development.
Here, date palm mite *O. afrasiaticus* may be excellent and more favorable food than date palm
pollen or corn pollen diets.

Total development time of *P. plumifer* females fed *O. afrasiaticus* (at 32 °C, 5.97 days) in the current study was shorter than for *P. plumifer* fed on *Tetranychus urticae* Koch at 30 °C was 6.60 days (Gorji et al. 2008), *Rhynchaphytoptus ficifoliae* (Keifer) at 25 °C was 8.73 days, (Louni et al. 2014), *Eotetranychus hirsti* Pritchard & Baker at 30 °C was 8.62 days (Shakarami and Bazgir 2017), *Tegolophus hassani* (Keifer) at 35 °C was 5.92 days (Al-Azzazy and Alhewairini 2020). The developmental time of immature females of *P. plumifer* fed on *T. urticae* at 35 °C (5.3 days) which was very close to the current results against *O. afrasiaticus* (Gorji et al. 2008). On the other hand, the development of *P. plumifer* immature females was longer in our study (5.35 d) than reported when fed on the red spider mite *Tetranychus cinnabarinus* (Boisduval) 3.8 days (Zaher et al. 1969). The developmental time of 6.72 days for *P. plumifer* females fed on the date palm pollen in the current study was shorter when compared to 10.5 days reported by Zaher et al. (1969).

Likewise, the development time of 6.89 d for *P. plumifer* females fed corn pollen in our study was short when compared to 10.00 days reported by (Khodayari *et al.* 2013). Contrasting our findings with those of Kouhjani-Gorji *et al.* (2008) and Hamedi *et al.* (2011) it can be concluded that when corn pollen was the only food source, immature development took longer, and adult female longevity and fecundity were decreased, altogether resulting in a significant reduction in r<sub>m</sub> of 0.112 day<sup>-1</sup>. However, the predator was able to develop and reproduce successfully on the corn pollen, which is consistent with the results of (Khodayari *et al.* 2013). Furthermore, *O. afrasiaticus*-fed *P. plumifer* developed quicker than their prey. For instance, *O. afrasiaticus* female took about 12.45 days to mature at 30 °C (Al-Jboory 2010). The developmental time of *P. plumifer* fed on *O. afrasiaticus* in this study was also shorter than the developmental time reported for potential mite prey such as black flat mite, *Brevipalpus phoenicis* (Geijskes) 18.81 days at 26 °C (Lal 1979), *T. urticae* 6.7 days at 29.4 °C (Carey and Bradley 1982), and red palm mite, *Raoiella indica* Hirst 13.33 days at 30 °C (Fidelis *et al.* 2019).

The capability of the predator to develop quicker than prey species has significant implica-
tions for augmentative biocontrol. It implies that *P. plumifer* augmentative releases might help
to eradicate pest populations in date palm orchards. In the current study, when the predator
fed on natural prey source *O. afrasiaticus*, it exhibited higher indicators of oviposition period,
total fecundity, and adult longevity compared to when it fed on date palm pollen or corn
pollen. The maximum fecundity was attained when *P. plumifer* fed on *O. afrasiaticus* (64.42
eggs/female). This value was higher when compared to mites that fed on *T. urticae* (45.23
eggs/female) (Kouhjani-Gorji *et al.* 2012), on *R. ficifoliae* (28.47 eggs/female) (Louni *et al.*
2014), on *E. hirsti* (35.71 eggs/female) (Shakarami and Bazgir 2017), and on *O. niloticus*
(50.80 eggs/female) (Al-Azzazy and Alhewairini 2020).

These findings suggest that a diet of *O. afrasiaticus* is more suitable for *P. plumifer*
reproduction. *Phytoseius plumifer* produced more eggs with the *O. afrasiaticus* diet suggest
that the quality of macronutrients necessary for ovary development and egg maturation are
greater in *O. afrasiaticus*. Adult longevity of *P. plumifer* was also affected by diet type in
this study; females and males lived longer when fed *O. afrasiaticus*. The female longevity in
this study (39.44 ± 2.15 days) was close to the longevity of females feeding on *T. urticae* in a
study by Kouhjani-Gorji *et al.* 2008 (43.83 ± 1.07 days) at 30 °C. *Phytoseius plumifer* females
consumed on an average of 739.26 individuals of *O. afrasiaticus* during the whole life-span in this study, while they consumed 346 individuals of *T. cinnabarinus* (Zaher *et al.* 1969), and 517.33 individuals of *T. urticae* (Al-Azzazy and Alhewairini 2020).

The life table parameters of *P. plumifer* were affected by diet. Many biological studies have affirmed that the high-quality food sources led to increased values in life table parameters (Jiale *et al.* 2016; Ali *et al.* 2023; Barzkar *et al.* 2023). The highest intrinsic rate of increase ($r_m$) in the current study was recorded when *P. plumifer* fed on *O. afrasiaticus* (0.278 d⁻¹). This value is greater than those stated by Hamedi *et al.* 2011 when *P. plumifer* fed on *T. urticae* (0.200 at 26 °C), *E. hirsti* 0.180 at 30 °C (Shakarami and Bazgir, 2017), *R. ficifoliae* 0.154 at 25 °C (Louni *et al.* 2014), corn pollen 0.112 at 27 °C (Khodayari *et al.* 2013) and *Polyphagotarsonemus latus* (Banks) 0.19 at 26 °C (Fouly *et al.* 2019).

Moreover, the values of (Ro), ($r_m$) and ($\lambda$) of *P. plumifer* at 32 °C and 50% RH in this study are also higher than that of some other predacious mites on the same food source, *O. afrasiaticus*, including *Euseius scutalis* (Athias-Henriot) (Ro= 13.60, $r_m$ = 0.161 and $\lambda$ = 1.17 at 26 °C and 70% RH) (Al-Shammery 2010), *Cydnoseius negevi* (Swirski and Amitai) (Ro= 17.35, $r_m$ = 0.19 and $\lambda$ = 1.21 at 35 °C and 35% RH), and *Neoseiulus barkeri* Hughes (Ro= 13.84, $r_m$ = 0.16 and $\lambda$ = 1.17 at 35 °C and 35% RH) (Negm *et al.* 2014), which shows that the use of *O. afrasiaticus* in *P. plumifer* mass rearing is appropriate. In view of this, *P. plumifer* could be a useful biological control agent for date palm mite *O. afrasiaticus*. According to (Kouhjani-Gorji *et al.* 2012), when testing *P. plumifer* at six constant temperatures, the highest intrinsic rate of increase (0.257) was recorded at 30 °C, which is close to the result of *P. plumifer* feeding on *O. afrasiaticus* ($r_m$ = 0.278) reported in the present study. The intrinsic rate of increase of *P. plumifer* when feeding on corn pollen is 0.112 (Khodayari *et al.* 2013), which is lower than when feeding on corn pollen reported in the present study ($r_m$ = 0.195). Previous studies have not assessed the effects of a diet of date palm pollen on life table parameters of *P. plumifer*. Moreover, the values of (Ro), ($r_m$) and ($\lambda$) of *P. plumifer* in this study are also higher than that of some other predacious mites when they fed date palm pollen, including *C. negevi* (Ro= 13.99, $r_m$ = 0.20 and $\lambda$ = 1.22 at 30 °C and 35% RH) (Alatawi *et al.* 2018), *Euseius scutalis* (Ro= 17.88, $r_m$ = 0.23 and $\lambda$ = 1.26 at 26 °C and 75% RH) (Fouly *et al.* 2013), and *A. swirskii* (Ro= 6.06, $r_m$ = 0.08 and $\lambda$ = 0.08 at 25 °C and 66% RH) (Riahi *et al.* 2017). This research provides valuable information into the life history traits and life table parameters of *P. plumifer* under different diets. The results contribute to our knowledge of the reproductive performance and population dynamics of this predacious mite species. Additional studies are needed to explore the possibility of using this predator under field conditions.

## Conclusion

This study indicates that *P. plumifer* exhibits favorable fecundity, and the capacity to establish populations using natural prey *O. afrasiaticus*. This suggests that *P. plumifer* can be utilized as a biocontrol agent of the date palm mite, *O. afrasiaticus*. Additionally, *P. plumifer* demonstrated the capability of development on alternative food sources, including date palm pollen and corn pollen, yielding favorable results, specifically when fed on date palm pollen. Moreover, date palm pollen is a supplementary source of food in critical periods when prey is absent or insufficient.

## Author contributions

This manuscript was drafted by Mahmoud M. Al-Azzazy and Saleh S. Alhewairini. Laboratory work and statistical analysis were performed by Mahmoud M. Al-Azzazy. Saleh S. Alhewairini planned and assisted with the implementation of this study.
Competing interests

The authors declare no competing interests.

Funding

No funding was provided for this study.

ORCID

Mahmoud M. Al-Azzazy ID https://orcid.org/0000-0002-2569-8770

Saleh S. Alhewairini ID https://orcid.org/0000-0003-2770-7412

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