Development, long-term survival, and the maintenance of fertility in Neoseiulus californicus (Acari: Phytoseiidae) reared on an artificial diet

Artificial diets for rearing Euseius scutalis (Acari: Phytoseiidae)

Mass rearing of the predatory mite Euseius scutalis (Athias-Henriot) using natural prey is costly and labor-intensive, limiting its application in biological pest control. Artificial diets may serve as alternative food sources; however, some studies should be previously conducted, to evaluate the possible biological consequences of their adoption. In this study, we compared the suitability of eight artificial diets, including a basic artificial diet (A) consisting of a combination of 10% honey, 10% sucrose, 5% tryptone, 5% yeast extract, 10% egg yolk, and 60% distilled water (w/w), along with seven other diets, each consisting of 80% of diet A enriched with date palm pollen (B), Typha pollen (C), Ephestia kuehniella eggs (D), Helicoverpa armigera hemolymph (E), a mixture of date palm pollen and E. kuehniella eggs (F), Tetranychus turkestani adults (G), and hen's liver (H). The data showed that E. scutalis was able to complete its development on all tested diets. Oviposition of the predator was observed on all diets, except for diets E and H. Females reared on diets B and F had the shortest adult pre-oviposition period (APOP), while those on diet B had the shortest total pre-oviposition period (TPOP). Furthermore, the number of oviposition days and fecundity were highest on diets B, D and F. Diets B and F resulted in significantly higher intrinsic (r) and finite (λ) rates of increase than the other diets, with values statistically similar to those obtained on D. The lowest values of r and λ were recorded on diet G. Based on our results, date palm pollen, E. kuehniella eggs or their mixture added to the basic diet A are more beneficial than other options for use in artificial diets for the mass rearing of E. scutalis.

Potential of a winterschmidtiid prey mite for the production of the predatory mite Neoseiulus californicus (Acari: Phytoseiidae)

Mass rearing of the predatory mite Neoseiulus californicus (McGregor) (Acari: Phytoseiidae) using natural (prey) methods is costly and laborious, limiting its application in the biological control of pests. A high-production, low-cost method using a prey substitute would help to relieve this problem. Oulenziella bakeri Hughes (Acari: Winterschmidtiidae) could be an alternative prey source, but studies on the reproductive parameters of N. californicus under rearing conditions are lacking. This study evaluated the potential of O. bakeri as an alternative prey in N. californicus rearing by comparing developmental parameters among N. californicus reared on three diets based on an age-stage two-sex life table. We found that the preoviposition period and developmental time of N. californicus did not vary based on diet. The fecundity of N. californicus adults reared on O. bakeri was 29.8 eggs per female, which was lower than that of adults reared on Tetranychus urticae Koch (Acari: Tetranychidae) (42.9 eggs per female); there was no significant difference between O. bakeri and apple pollen (30.2 eggs per female). The oviposition rate of mites fed on O. bakeri was 69% of that fed on T. urticae. Neoseiulus californicus reared on O. bakeri and apple pollen showed the same intrinsic rate of increase (0.25 per day), which was 86% of the rate of those fed on T. urticae. Compared with predatory mites reared on natural prey, N. californicus reared on O. bakeri had a high survival rate and good oviposition and population growth parameters, suggesting that O. bakeri is suitable for the rearing of N. californicus.

Strawberry pollen as a source of UV-B protection ingredients for the phytoseiid mite Neoseiulus californicus (Acari: Phytoseiidae)

BACKGROUND

A new physical control method using ultraviolet-B (UV-B) lamps and light-reflecting sheets (UV method) significantly suppressed a spider mite population on greenhouse strawberries. Although UV-B radiation may adversely affect the survival of phytoseiid mites, previous research has suggested that Neoseiulus californicus can improve its survival on exposure to UV-B irradiation by consuming antioxidants contained in tea and peach pollen. In this study, we evaluated strawberry pollen as an alternative food source for N. californicus and examined whether antioxidants in the pollen mitigated UV-B damage to N. californicus.

RESULTS

The fecundity of N. californicus females reared on Tetranychus urticae decreased on shifting their diet to pollen. By contrast, females reared continuously on strawberry pollen produced as many eggs as females reared continuously on T. urticae. Survival and fecundity after UV-B irradiation were higher in females on the pollen diet. Oxygen radical absorbance capacity analysis revealed that the high antioxidant activity of strawberry pollen was due to four hydroxycinnamoyl spermidine derivatives.

CONCLUSION

Strawberry pollen was an adequate alternative food source for N. californicus. Feeding on strawberry pollen, which contains spermidine derivatives with high antioxidant activity, mitigated UV-B damage. This shows the potential of combining the UV-method with N. californicus for controlling T. urticae in strawberries.

Productivity of Neoseiulus bicaudus (Acari: Phytoseiidae) Reared on Natural Prey, Alternative Prey, and Artificial Diet

The predatory mite, Neoseiulus bicaudus (Wainstein), is a potential biological control agent against spider mites and thrips. The objective of this experiment was to compare the effects of three diets on the life table of N. bicaudus. The three diets were 1) Tetranychus turkestani (Ugarov & Nikolskii) (Acari: Tetranychidae), the natural prey of N. bicaudus; 2) Tyrophagus putrescentiae (Schrank) (Acari: Acaridae), an alternative prey; and 3) artificial diet primarily consisting of decapsulated shrimp cysts, egg yolk, and honey. The computer simulation was used to project the population growth of N. bicaudus fed on different diets. The preadult developmental time (3.83 d) of N. bicaudus was shortest, and the intrinsic rate of increase (r = 0.2782 d-1) and the net reproductive rate (R0 = 18.98 offspring) were highest when reared on the alternative prey Ty. putrescentiae. The total development time (7.37 d) was longest, and the population parameters were the lowest (r = -0.0081 d-1, R0 = 0.85 offspring) when N. bicaudus was reared on artificial diet. The population projection showed that the population of N. bicaudus reared on Ty. putrescentiae could increase fast. Our results showed that the Ty. putrescentiae was the most suitable prey for mass rearing of N. bicaudus. The artificial diet could not support the N. bicaudus population and needs to be improved.

Delayed mite hatching in response to mechanical stimuli simulating egg predation attempts

Delayed or induced hatching in response to predation risk has been reported mainly in aquatic systems, where waterborne cues from predators and injured neighbouring eggs are available. Newly emerged larvae of the terrestrial predatory mite Neoseiulus womersleyi are vulnerable to predation by con- and heterospecific predatory mites, whereas their eggs are not. We examined whether N. womersleyi embryos delay hatching in response to artificial mechanical stimuli that simulates egg predation attempts. When embryos near the hatching stage were artificially stimulated every 5 min for 60 min, most stopped hatching for the duration of the 60-min period, whereas unstimulated embryos did not. Stimulated embryos resumed hatching when the treatment was stopped, and the proportion of hatched stimulated embryos caught up with that of unstimulated embryos within 120 min after stimuli stopped. Since hatching did not stop in response to changes in gravity direction, the effect of direct mechanical stimuli on the eggs was considered a proximate factor in delayed hatching. These results suggest that N. womersleyi embryos recognise immediate predation risk via mechanical stimuli, and delay hatching until the predation risk is reduced.

Supplementary food for Neoseiulus californicus boosts biological control of Tetranychus urticae on strawberry

BACKGROUND

A wide range of supplementary food resources can be offered to generalist predatory mites to improve their survival and reproduction and enhance their persistence in the environment. We investigated the relative suitability of different pollen types for the survival and reproduction of Neoseiulus californicus and its life history on a mixed diet of pollen and prey. We also evaluated the population dynamics of Tetranychus urticae in the presence of N. californicus with or without pollen, and in comparison to Phytoseiulus macropilis.

RESULTS

Survival and reproduction of N. californicus adults were satisfactory on exclusive diets of T. urticae, cattail pollen, palm pollen and bee pollen. However, mites did not reproduce when fed only pollen during both immature and adult stages. Both predatory mites successfully controlled T. urticae. Although the specialist P. macropilis was more efficient in suppressing the pest population in the short term, it abandoned plants at low prey densities, whereas N. californicus performed better and persisted longer under prey scarcity.

CONCLUSION

N. californicus is an efficient biological control agent of T. urticae and the provision of supplementary food could retain them in the crop prior to the arrival of the pest or in periods of prey scarcity. © 2019 Society of Chemical Industry.

Attempt to Develop Cost-Effective Rearing of Amblyseius swirskii (Acari: Phytoseiidae): Assessment of Different Artificial Diets

Commercial production of Amblyseius swirskii Athias-Henriot based on storage mites needs both space and labor to maintain large cultures of these prey, and also may lead to health problems for workers. Therefore, the accessibility of a suitable artificial diet could eliminate the mentioned problems; however, the artificial diets must support the persistent production of high quality progeny. This study endeavored to find a more easily available and cheaper nutrient that may further reduce the cost of diet production for A. swirskii. The predator's performance was determined when it was fed on a basic artificial diet (AD1) composed of honey, sucrose, tryptone, yeast extract, and hen egg yolk, and on eight other artificial diets consisting of 80% AD1 enriched with different nutrients including maize pollen (AD2), hemolymph of Plusia gamma L. (AD3), Ephestia eggs (AD4), Artemis cysts (AD5), Ephestia last-instar larvae (AD6), multivitamin syrup (AD7), bovine serum albumin (AD8), and bull sperm (AD9). The lowest development time was on AD2. The highest value of fecundity and oviposition period were observed on AD5, followed by AD2 and AD4. The intrinsic rate of increase (r) and the finite rate of increase (λ) reached the maximal value on AD5. Feeding on AD2 and AD5 resulted in highest value of R0 (net reproductive rate). Our results indicated that Artemia cysts and maize pollen had better potential to be used as nutrient in artificial diet for mass production of A. swirskii. Overall, it seems that AD2 is the most cost effective than others.

The use of the cannibalistic habit and elevated relative humidity to improve the storage and shipment of the predatory mite Neoseiulus californicus (Acari: Phytoseiidae)

This study investigated the feasibility of using the cannibalistic habits of the mite Neoseiulus californicus (McGregor) and controlling the relative humidity (RH) to prolong the survival time during the storage or shipment of this predatory mite. Three-day-old mated and unmated females were individually kept at 25 ± 1 °C in polypropylene vials (1.5 mL), each containing one of the following items or combinations of items: a kidney bean leaf disk (L), N. californicus eggs (E), and both a leaf disk and the eggs (LE). Because the leaf disk increased the RH in the vials, the RH was 95 ± 2 % under the L and LE treatments and 56 ± 6 % under the E treatment. The median lethal time (LT50) exceeded 50 days for the mated and unmated females under the LE treatment. However, it did not exceed 11 or 3 days for all females under the L or E treatments, respectively. Under the LE treatment, the mated and unmated females showed cannibalistic behavior and consumed an average of 5.2 and 4.6 eggs/female/10 days. Some of the females that survived for LT50 under each treatment were transferred and fed normally with a constant supply of Tetranychus urticae Koch. Unmated females were provided with adult males for 24 h for mating. Only females previously kept at LE treatment produced numbers of eggs equivalent to the control females (no treatment is applied). The results suggested that a supply of predator eggs and leaf material might have furnished nutrition and water vapor, respectively, and that this combination prolonged the survival time of N. californicus during storage. Moreover, this approach poses no risk of pest contamination in commercial products.

Artificial and factitious foods support the development and reproduction of the predatory mite Amblyseius swirskii

The generalist predatory mite Amblyseius swirskii Athias-Henriot (Acari: Phytoseiidae) was reared on Ephestia kuehniella Zeller eggs (Lepidoptera: Pyralidae), decapsulated dry cysts of the brine shrimp Artemia franciscana Kellogg (Anostraca: Artemiidae), and on meridic artificial diets (composed of honey, sucrose, tryptone, yeast extract, and egg yolk) supplemented with pupal hemolymph of the Chinese oak silkworm Antheraea pernyi (Guérin-Méneville) (Lepidoptera: Saturniidae) (AD1), with E. kuehniella eggs (AD2) or with A. franciscana cysts (AD3). Development, reproduction and predation capacity of the predatory mites were assessed in the first (G1) and sixth generation (G6) of rearing on the different diets. Immature survival rates in G1 were similar on all diets (96.8-100 %). After six generations, however, survival of A. swirskii was significantly reduced on all diets except on A. franciscana cysts. Oviposition rates did not differ between generations when females were fed on E. kuehniella, AD2 or AD3. The total number of deposited eggs was similar among diets except in G6 where the females fed on A. franciscana cysts produced more eggs than those maintained on E. kuehniella eggs. On most diets the intrinsic rates of increase in G1 were superior to those in G6, except for predators supplied with A. franciscana cysts where no differences were observed among generations. Female mites did not lose their capacity to kill first instar Frankliniella occidentalis (Pergande) (Thysanoptera: Thripidae) after six generations on the different diets, but predation rates in G6 on E. kuehniella were lower than in G1. In conclusion, the different factitious and artificial diets tested in the present study supported the development and reproduction of A. swirskii for a single generation but fitness losses occurred to a varying degree after several generations on E. kuehniella eggs or the artificial diets. Artificial diet enriched with A. franciscana cysts yielded better results than the other artificial diets. Amblyseius swirskii performed best on decapsulated Artemia cysts indicating their potential for use in the mass production of the predator or to sustain its populations in the crop after release.