Juang-Horng Chong

Temperature Effects on the Development, Survival, and Reproduction of the Madeira Mealybug, Phenacoccus madeirensis Green (Hemiptera: Pseudococcidae), on Chrysanthemum

Abstract The Madeira mealybug, Phenacoccus madeirensis Green (Hemiptera: Pseudococcidae), has become an increasingly damaging pest in greenhouse ornamental production. Current management tactics of P. madeirensis require a regular chemical application schedule targeting the immature stages. Knowledge of the life cycle of P. madeirensis is important to the success of its management program. We investigated the effects of constant temperature (15, 20, 25, 30, 35, and 40°C) on the development, survival, and reproduction of P. madeirensis on chrysanthemum (Dendrathema x grandiflora Kitam.). We failed to establish colonies at 30–40°C. Between 15 and 25°C, the duration of development of all developmental stages were shortened at higher temperatures. The total duration of development of female mealybugs was ≈30 d at 25°C, 46 d at 20°C, and 66 d at 15°C. Developmental time of males was 3–9 d longer than females. Survival rates of individual instars ranged between 88 and 100% and were not influenced by temperature. Overall, >75% of eggs completed development to adulthood. Female mealybugs made up 50% of the adult populations in all temperature treatments. Adult longevity at 25°C was ≈3 and 20 d for males and ovipositing females, respectively. Females at 20°C produced the highest number of eggs (491 ± 38 eggs/female).

Host stage selection of the mealybug parasitoid Anagyrus spec. nov near sinope

The mealybug parasitoid Anagyrus spec. nov near sinope (Hymenoptera: Encyrtidae) is an undescribed parasitoid of the Madeira mealybug, Phenacoccus madeirensis Green (Homoptera: Pseudococcidae). We investigated the preference of Anagyrus spec. nov near sinope for six developmental stadia (first‐ and second‐instar nymphs, third‐instar immature females, third‐ or fourth‐instar immature males, pre‐reproductive adult females, and ovipositing adult females) of P. madeirensis and the fitness consequences of the host stage selection behavior. In the no‐choice test, Anagyrus spec. nov near sinope parasitized and completed development in all host stadia except third‐instar immature males. When all host stadia were offered simultaneously, the parasitoids preferred third‐instar immature and pre‐reproductive adult females. Dissection of the stung mealybugs revealed that the clutch size (number of eggs per host) was approximately four and three in the third‐instar and pre‐reproductive females, respectively, and one egg per first‐instar nymph. Parasitoids emerged from P. madeirensis parasitized at third‐instar or pre‐reproductive adult female completed development in the shortest duration, achieved a higher progeny survival rate, larger brood and body size, and the lowest proportion of males. We showed that the continued development of mealybugs had significant influence on the fitness of the parasitoids. Although deposited as eggs in first‐ or second‐instar nymphs, parasitoids emerged from mummies that had attained third‐instar or adult development achieved similar progeny survival rate, brood size, body size, and sex ratio as those parasitoids deposited and developed in third‐instar or adult mealybugs. By delaying larval development in young mealybugs, Anagyrus spec. nov near sinope achieved higher fitness by allowing the parasitized mealybugs to grow and accumulate body size and resources. We suggest that the fitness consequence of host stage selection of a koinobiont parasitoid should be evaluated on both the time of parasitism and the time of mummification.

Intraguild predation and interference by the mealybug predator Cryptolaemus montrouzieri on the parasitoid Leptomastix dactylopii

Abstract The compatibility of the encyrtid parasitoid Leptomastix dactylopii with the coccinellid beetle Cryptolaemus montrouzieri against the citrus mealybug, Planococcus citri, is determined by the extent of intraguild predation and interference by the predator. We tested the preference of the adults and fourth-instar larvae of C. montrouzieri for healthy mealybugs and parasitized mealybugs harboring 1-, 4-, 7- and 14-day-old parasitoid larvae. The experiments were conducted in no-choice (only unparasitized mealybugs or parasitized mealybugs of one parasitoid age were offered at one time) and choice (unparasitized and parasitized mealybugs of a specific age were offered simultaneously) tests. Both the adults and larvae of C. montrouzieri fed on unparasitized and parasitized mealybugs but strongly discriminated against the hardened mummies (14 days old). We also investigated the influence of the presence of C. montrouzieri to the foraging effectiveness of L. dactylopii. The level of parasitism by L. dactylopii was reduced from about 13 to 6% when the number of the C. montrouzieri was increased from zero to four. We recommended that the releases of C. montrouzieri should be conducted 14 days after the releases of L. dactylopii to reduce intraguild predation on the parasitized mealybugs and to avoid interference with the foraging parasitoids.

Influence of Temperature and Mating Status on the Development and Fecundity of the Mealybug Parasitoid, Anagyrus sp. nov. nr. sinope Noyes and Menezes (Hymenoptera: Encyrtidae)

Abstract Anagyrus sp. nov. nr. sinope Noyes and Menezes (Hymenoptera: Encyrtidae) is a new parasitoid of the Madeira mealybug, Phenacoccus madeirensis Green (Hemiptera: Pseudococcidae), a common pest in the greenhouses of the southeastern United States. The objectives of this study were to assess the influence of temperature (15, 20, 25, 30, and 35°C) and mating status (virgin and mated) on the life history of this parasitoid. Anagyrus sp. nov. nr. sinope is an arrhenotokous parasitoid with the mated females producing progeny with the proportion of males between 0.34 and 0.41. Parasitism rates ranged between 17 and 40% and increased with temperature. The number of progeny produced by the mated parasitoids increased from 8 at 15°C to 11 at 30°C, which were 10 and 50% lower, respectively, than that of virgin parasitoids. For females of either mating status, brood sizes averaged between 3.1 and 4.9 progeny per mummy. More than 94% of parasitoids successfully survived to adulthood between 15 and 30°C. No parasitoid completed development at 35°C. The developmental times of Anagyrus sp. nov. nr. sinope were 55, 25, 17, and 12 d at 15, 20, 25, and 30°C, respectively. Using a linear thermal summation model and a nonlinear Logan 6 model, we determined that the lower developmental threshold, upper developmental threshold, and optimal temperature to be 11.1, 35.0, and 30.3°C, respectively, and the thermal constant was 222.2 DD. The lifetime fecundity of Anagyrus sp. nov. nr. sinope were 58–71 progeny between 15 and 30°C. Mated females had significantly higher lifetime fecundity than virgin females. We expect Anagyrus sp. nov. nr. sinope to survive and reproduce within a temperature range commonly maintained in greenhouses.

Effects of Elevated Carbon Dioxide Levels and Temperature on the Life History of the Madeira Mealybug (Hemiptera: Pseudococcidae)

Atmospheric carbon dioxide concentrations and temperatures are increasing and, thus, the interactions between insect herbivores and their host plants in environments of elevated CO2 concentration a...

Progeny Fitness of the Mealybug Parasitoid Anagyrus sp. nov. nr. sinope (Hymenoptera: Encyrtidae) as Affected by Brood Size, Sex Ratio, and Host Quality

Abstract Anagyrus sp. nov. nr. sinope Noyes & Menezes (Hymenoptera: Encyrtidae) is a gregarious, koinobiont parasitoid of the Madeira mealybug, Phenacoccus madeirensis Green (Hemiptera: Pseudococcidae). We investigated effects of larval competition on development, survival, and progeny body size of the parasitoid over a range of brood sizes and sex ratios. We recorded the brood size, sex ratio, and fitness parameters of parasitoids developing from second instars and adult P. madeirensis. Adult mealybugs as hosts produce larger brood and progeny body sizes and more female progeny. Second instar P. madeirensis continued to develop after parasitism, and mummies achieved a more advanced developmental stage yielding parasitoid cohorts of larger brood and body sizes, female-biased sex ratio, and longer developmental time than mummies formed from younger host instars. Overall, the sexual composition within a brood had little or no effect on the development, survival and body size of the parasitoid progeny developing from second instar and adult mealybugs. Larval competition among brood-mates developing in adult mealybugs caused a reduction in the progeny tibial length with increasing brood sizes. In contrast, parasitoids developing from second instar mealybugs had a longer developmental time and little (although positive) or no response in the progeny tibial length to increasing brood size. We hypothesize that the continuous development of second instar mealybugs allows the hosts to accumulate additional resources, thus, reducing competition among parasitoid brood mates for limited resources. The continuous development of hosts of younger developmental stages after parasitism may have the potential to alter the direction and intensity of larval competition of the koinobiont gregarious parasitoid.

Influence of Temperature, Nourishment, and Storage Period on the Longevity and Fecundity of the Mealybug Parasitoid, Anagyrus sp. nov. nr. sinope Noyes and Menezes (Hymenoptera: Encyrtidae)

Abstract Anagyrus sp. nov. nr. sinope Noyes and Menezes (Hymenoptera: Encyrtidae) is a candidate for biological control of the Madeira mealybug, Phenacoccus madeirensis Green (Hemiptera: Pseudococcidae). P. madeirensis is a serious pest of horticultural crops in the southeastern United States. The first experiment studied the effect of temperature (15, 20, 25, 30, and 35°C) and feeding treatment (starved, hydrated with distilled water, and nourished and hydrated with diluted honey) on adult longevity of Anagyrus sp. nov. nr. sinope. Nourished and hydrated female parasitoids survived an average of 52.8 d at 15°C, which was 14 and 8 times longer than starved and hydrated females at the same temperature, respectively, and 8 times longer than nourished and hydrated females at 35°C. The second experiment studied the influence of feeding treatment on the reproduction of Anagyrus sp. nov. nr. sinope at 25°C. Nourished and hydrated female parasitoids lived (mean = 14.2 d) and reproduced (mean = 7 d) for a longer duration, parasitized more hosts (mean = 16), and produced more offspring (mean = 45) than starved or hydrated females. The third experiment assessed the longevity and reproduction of Anagyrus sp. nov. nr. sinope after storage for various durations (0, 1, 4, 7, 14, 21 d) at 15 and 25°C. Parasitoids stored at 15°C had increased longevity and a decreased reproductive period but similar parasitism rates and fecundity to those stored at 25°C. The results suggested that the parasitoids could be stored at 15 and 25°C for up to 14 d without significant reduction in fecundity after release.

Impacts of Parasitism on the Survivorship and Reproduction of the Madeira Mealybug (Hemiptera: Pseudococcidae)

This study was conducted to assess the impacts of parasitism by Anagyrus sp. nov. nr. sinope Noyes and Menezes on the reproductive potential and the survivorship of the Madeira mealybug, Phenacoccu...

Foraging Behavior of the Mealybug Parasitoid Anagyrus sp.nov. nr. sinope (Hymenoptera: Encyrtidae)

Anagyrus sp. nov. nr. sinope Noyes and Menezes (Hymenoptera: Encyrtidae) is a candidate biological control agent against the Madeira mealybug, Phenacoccus madeirensis Green (Hemiptera: Pseudococcidae). This study reported on the components of the oviposition behavior of Anagyrus sp. nov. nr. sinope in relation to 6 developmental stadia of P. madeirensis: crawlers, second-instar nymphs, third-instar immature females, third-instar immature males, prereproductive adult females, and ovipositing adult females. A behavioral sequence and a time budget were prepared for Anagyrus sp. nov. nr. sinope, indicating that the parasitoids foraging in a patch containing third-instar and prereproductive adult females had the highest probability to encounter and eventually parasitize a host. The parasitoids attacking third-instar and prereproductive adult females also spent the largest proportion of total foraging time in oviposition (67 and 69%, respectively) and had the longest handling time (997 and 655 sec per event, re...