مطلوبیت غذاهای جایگزین در تولید انبوه کنه شکارگر Neoseiulus californicus: فراسنجه‌های زیستی روی پودر قند و گرده‌های مختلف

توانایی شکارگرها برای تغذیه، رشد و تولیدمثل روی غذایی غیر شکار یک ویژگی مطلوب برای عوامل بیولوژیک است که بتوانند جمعیتشان را در زمان کمبود شکار حفظ کنند. در این پژوهش، ارزش غذایی سه تیمار غذایی شامل پودر قند (خاکی قند)، گرده زعفران و مخلوطی از گرده بادام و ذرت برای پرورش کنه شکارگر Neoseiulus californicus McGregor مورد ارزیابی قرار گرفت. طول دوره قبل از بلوغ (15.94 روز) به‌طور معنی‌داری روی تیمار غذایی پودر قند طولانی‌تر از گرده زعفران (6.70 روز) و ترکیب گرده بادام و ذرت (6.85 روز) بود. طول عمر افراد نر و ماده بالغ با تغذیه از گرده زعفران و مخلوط گرده بادام-ذرت طولانی‌تر از افراد تغذیه کرده از پودر قند بود.

به هر حال روی تمام تیمارهای غذایی مورد بررسی، طول عمر ماده‌ها بیشتر از نرها بود. افراد تغذیه کرده از پودر قند، علیرغم زنده‌مانی و طول عمر زیاد، هیچ گونه باروری نداشتند. میزان باروری روی گرده زعفران و مخلوط گرده بادام-ذرت به ترتیب 43.19 و 37.59 تخم/ماده بود. مقادیر مربوط به نرخ ذاتی افزایش جمعیت (r)، نرخ متناهی افزایش جمعیت (λ)، نرخ ناخالص تولیدمثل (GRR)، نرخ خالص تولیدمثل (R0) و مدت زمان طول یک نسل (T) روی گرده زعفران و مخلوط گرده بادام-ذرت بدون هیچ گونه اختلاف معنی‌داری به ترتیب 0.195 در مقابل 0.183 بر روز، 1.215 در مقابل 1.201 بر روز، 32.15 در مقابل 31.48 نتاج، 29.85 در مقابل 25.36 نتاج، و 17.41 در مقابل 17.68 روز بود.

نتایج نشان‌دهنده‌ی مطلوبیت گرده زعفران و مخلوط گرده بادام-ذرت به عنوان غذای جایگزین طعمه طبیعی در تولید انبوه کنه شکارگر N. californicus می‌باشد. اگرچه کارایی تولیدمثلی کنه شکارگر روی تیمار غذایی پودر قند ضعیف بود (فاقد باروری) اما به دلیل مطلوبیت آن در زنده‌مانی طولانی مدت کنه شکارگر، می‌توان از این تیمار غذایی برای نگهداری جمعیت کنه شکارگر در زمان کمبود تقاضا و یا در طول دوره عرضه کنه شکارگر استفاده نمود.

Background and Objectives: The ability of predators to feed, develop, and reproduce on non-prey food sources, such as pollen, is a desirable trait for biological agents to maintain their populations in the event of prey scarcity. Additionally, this trait is valuable for rearing predators in laboratories or mass-rearing purposes before release. Research has shown that pollen as a dietary supplement may increase the establishment of generalist predatory mites, thereby improving pest control by these mites. Pollen provides essential nutrients, including proteins, carbohydrates, lipids, amino acids, vitamins, flavonoids, and minerals;

however, pollen’s nutritional value can vary among plant species. In addition, phytosetid mite species vary in their ability to utilize pollen. Studies have shown that food sources, particularly those containing high percentages of protein and carbohydrates, are nutritionally valuable for rearing predators. Thus, our study aimed to compare the nutritional value of a powdered sugar diet (contains high carbohydrates) and saffron and the mixture of almond and maize pollen grains (contains high protein) for Neoseiulus californicus McGregor (Acari: Phytoseiidae) performance to optimize its mass-rearing.

Materials and Methods: In this research, we evaluated the nutritional value of powdered sugar (sugar dust), saffron pollen, and a mixture of almond and maize (almond+maize) pollen in mass-rearing of the predatory mite N. californicus. Life table studies were conducted under laboratory conditions at 25 ± 1°C, 60 ± 5% RH, and a photoperiod of 16:8 (L:D) h. Data analysis and population parameters (r, λ, GRR, R0, and T) were calculated using the TWOSEX-MSChart program. The means and standard errors of all parameters (duration of different life stages, fecundity, reproductive periods, longevities, and population growth parameters), were calculated by the bootstrap procedure. To obtain stable estimates, 100,000 bootstraps were used. Mean comparisons of the parameters were performed using the paired bootstrap test based on confidence interval.

Results: Individuals of N. californicus successfully developed from larva to adult when fed all tested diets. However, the pre-adult duration was significantly longer on the powdered sugar diet compared to the pollen diet. The individuals fed saffron pollen had the shortest pre-adult duration (6.70 days). The adult longevity of males and females fed on the pollen diets was longer than those fed on powdered sugar. Females lived longer than males on all the treatments. The highest average lifespan was for the individuals fed saffron pollen (58.33 days).

However, the longest life span belonged to one of the female individuals fed on the almond+maize pollen (90 days). Although individuals fed on powdered sugar exhibited high survival rates and long lifespans, they had no fecundity. However, the average fecundity on saffron and almond+maize pollens was 43.19 and 37.59 eggs/female, respectively. The values of the intrinsic rate of increase (r), finite rate of increase (λ), gross reproductive rate (GRR), net reproductive rate (R0) and mean generation time (T) on saffron pollen and almond+maize pollen were 0.195 versus 0.183 day[-1], 1.215 versus 1.201 day[-1], 32.15 versus 31.48 offspring, 29.85 versus 25.36 offspring and 17.41 versus 17.68 days, respectively, without any significant differences. The probability of newly laid eggs reaching the adult stage was 100%, 100%, and 91% on the saffron pollen, almond+maize pollen, and powdered sugar diet, respectively.

Discussion: Our results indicate that saffron and almond+maize pollens can be effectively used for the mass-rearing and conservation of the predatory mite N. californicus in biological programs. Although the reproductive efficiency of the predatory mite on the powdered sugar diet was poor (with no fecundity), this diet is suitable for the long-term survival of the predatory mite and can be used to maintain populations during periods of low demand or limited supply. The long lifespan of the powdered sugar diet may be related to its high carbohydrate content; however, the lack of fertility on this diet is due to its deficiency in protein and other essential nutrients. The protein content of pollen is believed to be one of the best indicators of nutritive quality as it is closely linked to the reproductive performance of consumers. The high efficiency of the predator on the saffron and almond+maize pollens is probably due to their high protein content.