Dionyssios P. Lykouressis

The Aphidiinae (Hymenoptera : Ichneumonoidea : Braconidae) of Greece

Keys for the identification of genera and species of the subfamily Aphidiinae which occur in Greece as well as the observed parasitoid — aphid relations on various host plants are presented.

Life table and biological characteristics of Macrolophus pygmaeus when feeding on Myzus persicae and Trialeurodes vaporariorum

The life table and biological characteristics of the predatory bug Macrolophus pygmaeus Rambur (Hemiptera: Miridae) were studied when the bugs were fed with Myzus persicae (Sulzer) (Homoptera: Aphididae) feeding on eggplant and with Trialeurodes vaporariorum Westwood (Homoptera: Aleyrodidae) feeding on tomato plants. The tests were done at five temperatures between 15 and 30 °C, using a L16:D8 photoperiod and 65 ± 5% r.h. Most eggs (range 85 to 90%) hatched at 15 and 20 °C. Incubation period was shortest at 27.5 °C (8.45 and 8.38 days on eggplant and tomato, respectively). Preoviposition was also shortest at 27.5 °C (5.10 and 4.75 days on eggplant and tomato, respectively) whereas fecundity was highest at 20 °C (213.90 and 228.25 eggs on eggplant and tomato, respectively). Maximum longevity of females was at 15 °C (122.40 and 129.35 days on eggplant and tomato, respectively). Mean generation time was longest at 15 °C on both host plants (122.75 and 124.64 days, respectively). The intrinsic rate of increase of M. pygmaeus was highest at 27.5 °C with similar values on eggplant (0.0981 day−1) and tomato (0.1040 day−1). Doubling time was shortest at 27.5 °C (7.06 and 6.67 days on eggplant and tomato, respectively) and, also, finite rate of increase was highest at 27.5 °C (1.1031 and 1.1096 on eggplant and tomato, respectively). The results show that the predator M. pygmaeus develops well on the aphid M. persicae or on the whitefly T. vaporariorum, both of which are important pests of vegetable crops. This predator is also well adapted to the temperatures that occur both in greenhouses and in the open field in the Mediterranean region. Compared to other natural enemies of whiteflies, such as Encarsia formosa Gahan (Hymenoptera: Aphelinidae), Macrolophus pygmaeus can increase at relatively low temperatures.

The influence of temperature, photoperiod and plant type on the predation rate of Macrolophus pygmaeus on Myzus persicae

The effect of temperature and photoperiod on the rate of predation of nymphs and adults of the predator Macrolophus pygmaeus was studied using Myzus persicae prey feeding on egg-plant and pepper plants. The experiments were conducted at three photoperiods (16L:8D, 12L:12D and 8L:16D), three temperatures (20, 25 and 30 °C), and at 65% r.h. The rate of predation increased with temperature. Predation rate was affected by photoperiod on pepper but not on egg-plant. Females and fifth instar nymphs were the most voracious stages followed by third and fourth instar nymphs and males. First and second instar nymphs consumed far fewer aphids. Predation rate was higher on leaves of pepper than egg-plant, especially at 30 °C. Variation in the efficacy of this predator is discussed.

Thermal Requirements for Development of the Polyphagous Predator Macrolophus pygmaeus (Hemiptera: Miridae)

Abstract The effect of temperature on the duration of embryonic and nymphal development as well as on the preoviposition period of the polyphagous predator Macrolophus pygmaeus Rambur was studied in the presence and in the absence of prey on eggplant, pepper-plant, and tomato at 15, 20, 25, 27.5, 30, and 35°C, with 65 ± 5% RH and photoperiod of 16:8 (L:D) h. The aphid Myzus persicae (Sulzer) was used as prey on eggplant and pepper-plant and the whitefly Trialeurodes vaporariorum (Westwood) on tomato. The data obtained were used for the estimation of the thermal requirements of this predator. The temperature threshold for egg development was found as 7.61 and 6.92°C, for nymphal development in the presence 8.74 and 9.19°C and in the absence of prey 8.21 and 9.29°C, for preimaginal development 8.68 and 8.79°C, for preoviposition 7.58 and 6.96°C, and finally for egg-to-egg development 8.48 and 8.51°C on eggplant with M. persicae and on tomato with T. vaporariorum, respectively. On pepper-plant the temperature threshold for nymphal development was 8.26 and 8.23°C in the presence and in the absence of prey, respectively. The values of temperature threshold for development of the various nymphal stages were similar. It was also found that the slopes of the linear regressions between the rate of nymphal development and temperature were not significantly different among the different host plants in the presence and in the absence of prey. Also, the slopes of the linear regressions concerning the development of each nymphal stage with temperature were not found to differ significantly among the host plants in the presence and in the absence of prey. The thermal constant for egg development was estimated as 177 and 182, that for nymphal development in the presence 269 and 253 and in the absence of prey 332 and 306, for preimaginal development 439 and 431, for preoviposition 100 and 98 and finally that of egg-to-egg development 541 and 533 degree-days when fed on M. persicae on eggplant and on T. vaporariorum on tomato, respectively. On pepper-plant the degree-days for nymphal development was 280 and 361, in the presence and in the absence of prey, respectively. The temperature threshold for development was not found to differ among the host plants in the presence and in the absence of prey. However, the degree-days were significantly different between the presence and absence of prey on each host plant; the thermal constant in the absence of prey was estimated as an average of 1.21 times of that in the presence of prey. The results show that M. pygmaeus can establish, develop, and oviposit even in the absence of prey in relatively low temperatures and hence it can be released early in the season for an earlier and more effective control of whiteflies and aphids on vegetables.

Myzus persicae (Homoptera: Aphididae) as Suitable Prey for Macrolophus pygmaeus (Hemiptera: Miridae) Population Increase on Pepper Plants

Abstract Life table parameters and other biological characteristics were estimated for the predator Macrolophus pygmaeus Rambur (Hemiptera: Miridae) when fed on pepper plant/leaves with or without prey Myzus persicae (Sulzer) (Homoptera: Aphididae). The experiments were conducted at 15, 20, 25, and 30°C, under a photoperiod of 16:8 (L:D) h and at 65 ± 5% RH. Egg incubation was shortest at 30°C (10.5 d), egg hatch percentage reached 90% at 20°C, sex ratio was 78% at 25°C, and preoviposition period was shortest at 25°C (6.1 d). Only females with access to prey were able to reproduce. Fecundity was highest at 20°C (203.9 eggs). Females and males survived longer at 15°C (120.7 and 132.9 d, respectively). When provided with prey, M. pygmaeus can increase its numbers at all temperatures tested. Its intrinsic rate of increase and doubling time were highest at 25°C (0.0958 d−1 and 7.2 d, respectively). The lowest temperature threshold for population increase was 9.06°C. In the absence of prey, the predator did not oviposit, but females and males survived for a relatively long time at 15°C (26.5 and 28.7 d, respectively) and for a shorter time as temperature increased. The results indicate that M. pygmaeus performs very well when it feeds on the aphid M. persicae on pepper plants. Although the pepper plant can support adults, it does not permit population increase when prey is not available. However, these results are discussed with other findings in the context of a better and more effective use of this predator for biological control of M. persicae on pepper plant.

Influence of Light-Dark Phase, Host Plant, Temperature, and Their Interactions on the Predation Rate in an Insect Predator

Abstract The predation rate per hour of Macrolophus pygmaeus Rambur (Hemiptera: Miridae) under light and dark phase was examined in relation to the host plant, photoperiod, temperature, and life stage of the predator. Individuals from each nymphal stage plus adults of both sexes of M. pygmaeus were put individually into petri dishes on an eggplant or pepper plant leaf infested with nymphs of Myzus persicae (Sulzer) (Homoptera: Aphididae). The experiments were conducted at three photoperiods (8:16, 12:12, and 16:8 h [L:D]) and temperatures (20, 25, and 30°C) on eggplant and pepper plants. Generally, the predation rate was significantly higher in the dark than in the light phase, particularly in the case of larger instars and adults. Interactions between factors showed that the preference of this predator to feed at night is much higher on pepper plants than on eggplant, and this difference is more prominent at 30°C. The importance of these results in understanding foraging behavior and how aspects of this behavior affect the predator’s potential in biological control are discussed.

Time Allocation of Activities of Two Heteropteran Predators on the Leaves of Three Tomato Cultivars with Variable Glandular Trichome Density

Abstract Plant glandular trichomes can confer protection from herbivores, but may also affect natural enemies. We studied time allocation of activities (inactive, moving, probing, feeding, and grooming) of nymphs of the predatory bugs Macrolophus pygmaeus and Orius niger on the upper surface of tomato leaflets from the cultivars Dombito, Elxis, and H30. In H30, which had the highest density of type VI glandular trichomes on the upper surface, both insects spent more time in grooming their tarsi and rostrum than the other two cultivars. In Dombito and Elxis, which have trichome densities that didn’t differ much, no significant differences were observed in time allocation of activities for both insects. When averaged across cultivars, younger instars of M. pygmaeus spent less time on probing and more time on grooming, whereas for O. niger, the nymphs of first stage spent more time on grooming and less on movement than the nymphs of older stages. Between species, O. niger first instars groomed more and walked less than M. pygmaeus, whereas there were no detected differences between the other instars tested.

Nettle extract effects on the aphid Myzus persicae and its natural enemy, the predator Macrolophus pygmaeus (Hem., Miridae)

Abstract:  The effect of water extract of Urtica urens L. on the biological characteristics and population parameters of Myzus persicae (Sulzer) and its natural enemy, the polyphagous predator Macrolophus pygmaeus (Rambur) was investigated on eggplants. Plant material was extracted in deionized water (1 : 5 w/w) for 24 h. Three applications were made at 5‐day intervals using the nettle extract, with deionized water as the control. The effect of the extract on survival, duration of nymphal development, pre‐reproductive period, fecundity and longevity of both insects was studied at conditions of 25 ± 1°C, 65 ± 5% relative humidity and photoperiod of 16 : 8 h (light : dark). The results showed that the application of nettle extract significantly reduced the fecundity of M. persicae (20% on average) but did not result in a substantial lowering in its intrinsic rate of population increase. However, the predators biological characteristics and population parameters were not affected by the application of this plant extract. The importance of these results for the use of nettle extract in the management of M. persicae along with its compatibility with the use or conservation of M. pygmaeus is discussed.

Plant food effects on prey consumption by the omnivorous predator Macrolophus pygmaeus

Omnivorous predatory Heteroptera are important biological control agents of pests in several crops. They can feed on plant food resources that may positively affect their biological characteristics. In the current paper, the influence of leaves and flowers on the predation rate of the omnivorous predator Macrolophus pygmaeus (Rambur) (Hemiptera: Miridae) was investigated. Its predation rates were recorded on prey offered on (a) a single leaf of tomato, pepper or black nightshade (Solanum nigrum), or (b) a leaf of pepper or S. nigrum plus flowers of pepper or S. nigrum, respectively. In all cases the aphid Myzus persicae (Sulzer) (Homoptera: Aphididae) was used as prey at densities of 4, 8, 12, 16, 20 and 24 nymphs of the second instar. The experiments were conducted in petri dishes at 25 ± 1°C and prey consumption was evaluated after 24 h. The predation rate of M. pygmaeus was significantly higher on leaves of S. nigrum than on those of pepper at the prey density of 20 prey items. Therefore, the hypothesis that increased predation rates should occur on plants of lower suitability for development or reproduction was not supported under our experimental conditions. The flower availability did not alter the prey consumption among the prey densities on S. nigrum. However, the presence of a pepper flower caused a significant decrease in the predation rates on pepper leaves, at prey densities higher than eight prey items. Thus, pepper flowers can provide the predator with nutrient sources that may partially substitute for prey consumption, with practical implications in biological control.

Effect of Temperature on Development and Survival of the Parasitoid Pnigalio pectinicornis (Hymenoptera: Eulophidae) Reared on Phyllocnistis citrella (Lepidoptera: Gracillariidae)

Abstract Laboratory studies were conducted to assess the effect of temperature on the development and survival of the indigenous parasitoid Pnigalio pectinicornis L. on the citrus leaf miner Phyllocnistis citrella Stainton as host, fed on leaves of Citrus sinensis L. Osbck cultivar Washington navel and Citrus reticulata Blanco cultivar Clementine. Experiments were conducted at five constant temperatures ranging from 15 to 32.5°C, with 60 ± 10% RH and a photoperiod of 14:10 (L:D) h. The relationship between the developmental rate and temperature was determined using both linear and nonlinear (Lactin’s formula) models. Developmental time of immature stages tended to be shorter as the temperature increased the range from 15 to 30°C. Mortality was greater at the temperatures extreme tested. Both linear and nonlinear models provided a reliable fit of developmental rates versus temperature for all immature stages. Developmental thresholds that were estimated by the linear model for eggs were higher than those estimated by the nonlinear model. However, higher values of the low developmental threshold for larva and pupa stage of P. pectinicornis were estimated by the Lactin-2 model than that by the linear model. The potential of these models to predict the phenology of this parasitoid and its biological characteristics found in this study are discussed for its proper use as a biological control agent.