Shaaban Abd-Rabou

Incidence of Parasitoids and Parasitism of Bemisia tabaci (Homoptera: Aleyrodidae) in Numerous Crops

Abstract Understanding the relationship of parasitoids with their insect hosts and crop plants is needed to develop good management strategies for Bemisia tabaci (Gennadius), a whitefly pest. The abundance and establishment of parasitoids of B. tabaci B-biotype were tested with taxonomically diverse plants in the greenhouse (7 plant species) and in the field (16 plant species in Egypt). Greenhouse tests were conducted on plants free of whitefly nymphs to avoid this influence on parasitoid behavior, and field tests were conducted in crops with feral populations of B. tabaci. In the greenhouse, the parasitoid, Encarsia pergandiella Howard, was most abundant on Vigna unguiculata (L.) Walpers, followed by Gossypium hirsutum L. The propensity for this parasitoid to forage on the bottom leaf surface compared with the top surface varied among crops (45–90% were on the bottom leaf surface) and over time (≈50% were on the bottom leaf surface around sunrise, whereas ≈90% were on the bottom surface by mid-day). Inundative releases of laboratory-reared parasitoids, Eretmocerus mundus (Mercet), into field crops increased parasitization rates in all crops tested. Some crops (e.g., two Brassica species and V. unguiculata) were more conducive to parasitism of B. tabaci than other crops (e.g., Cucumis sativus L. and Lycopersicon esculentum Miller). Findings from this research may be useful in the enhancement and conservation of parasitoids of Bemisia.

Survey of Reproductive Host Plants of Bemisia tabaci (Hemiptera: Aleyrodidae) in Egypt, Including New Host Records

ABSTRACT: A field survey was conducted on the reproductive host plant species of the Bemisia tabaci (Gennadius) complex throughout Egypt. Infested plants were collected during each month of the year. Bemisia tabaci completed its development on 118 species of plants in 79 genera belonging to 28 families. The family Asteraceae (= Compositae) included 23 host plant species (20% of the total) belonging to 16 genera, while the family Fabaceae (= Leguminosae) included 17 host plant species belonging to 13 genera. The study revealed six new reproductive host plants consisting of five species and one subspecies in the families Asteraceae, Fabaceae, Piperaceae, Plantaginaceae and Portulacaceae. About 70% of the host plants are new host records for Egypt. Several recent studies have mistakenly cited a previous list of B. tabaci hosts in Egypt by erroneously referring to an early world host list as being a list of hosts in Egypt. The results of this study have implications on whitefly ecology and management.

Survey of Natural Enemies of Whiteflies (Hemiptera: Aleyrodidae) in Egypt with New Local and World Records

ABSTRACT Whiteflies (Hemiptera: Aleyrodidae) are some of the most problematic global pests of agricultural crops. Yet, natural enemies help control whiteflies. A field survey was conducted to identify and record the natural enemies associated with whiteflies in Egypt. Fifty-two natural enemies (29 species of parasitoids, 8 species of pathogens, and 15 species of predators) were found attacking or isolated from 14 whitefly species in Egypt. New world records are reported herein for two parasitoids [Encarsia lutea Masi and Eretmocerus mundus (Mercet)] on eight species of whiteflies, and for three predators [Chilocorus bipustulatus L., Chrysoperla carnea (Stephens), and Coccinella septempunctata L.] on a single whitefly species [Siphoninus phillyreae (Haliday)]. In addition, new local records of natural enemies on whiteflies are reported; this is the first local report of six predators and three entomopathogenic fungi of whiteflies in Egypt. This work helps in defining the natural enemies of whiteflies in and near agricultural communities.

Climate Change and Bemisia tabaci (Hemiptera: Aleyrodidae): Impacts of Temperature and Carbon Dioxide on Life History

ABSTRACT Climate change is relevant to life around the globe. A rise in ambient temperature and carbon dioxide (CO2) may have various impacts on arthropods such as altered life cycles, modified reproductive patterns, and changes in distribution. The sweetpotato whitefly, Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae), is a global pest responsible for significant losses of agricultural yields annually. This study was conducted to determine the impacts of changing temperature and CO2 levels on selected life history parameters of B. tabaci biotype B. Populations were established at three temperature regimes (25,28, and 33°C), and each population was evaluated in all three environments. Collard, Brassica oleracea ssp. acephala de Condolle (Brassicaceae), was used as the host. These results were based on data from 5 to ≈30 generations. Oviposition, nymphal survival, and reproduction were significantly affected by temperature, with net reproductive success declining to 36.4% at 33°C. Overall, 28°C was most favorable for whitefly fitness. However, the optimal temperature for B. tabaci reproduction may be between 28 and 33°C. There were no temperature effects on total nonstructural carbohydrate concentrations in collard, and impacts of the host plant on whitefly development in the different environments were determined to be minimal. An environment of enriched CO2 (750 ppm) was not observed to have an adverse effect on whitefly reproduction. Temperature was negatively correlated with adult body size. Length and width of males and females were affected by temperature. Data regarding population dynamics of B. tabaci in response to climate change are important for accurate predictions and improving management practices.

Survey of Natural Enemies of the Sweetpotato Whitefly (Hemiptera: Aleyrodidae) in Ten Vegetable Crops in Egypt

Abstract The sweetpotato whitefly, Bemisia tabaci (Gennadius) is a worldwide pest in diverse agroecosystems. There are numerous species of predators and parasitoids that are associated with this pest. Climate and species of vegetation can dramatically affect the distribution and incidence of these natural enemies. A field survey was conducted to determine the incidence of the primary natural enemies of B. tabaci in 10 vegetable crops in Egypt. Fifteen species of natural enemies of B. tabaci were observed, including 5 species of predators and 10 species of parasitoids. Coccinella septempunctata L. was the most commonly found predator, and it was found in four of the crops. The parasitoids consisted of four species of Encarsia and six species of Eretmocerus which represents 71% of the known aphelinid parasitoid species of B. tabaci in Egypt. Eretmocerus aegypticus Evans and Abd-Rabou was the most commonly encountered parasitoid species; it was found in five of the crops. To date, this species has only been reported in Egypt. These results help define the diversity of natural enemies of B. tabaci among vegetable crops.

Inundative field releases and evaluation of three predators for Bemisia tabaci （Hemiptera： Aleyrodidae） management in three vegetable crops

Abstract  The sweetpotato whitefly, Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae), is a global pest on numerous crops, including vegetables. Weekly inundative releases of a coccinellid predator (Coccinella undecimpunctata L. [Coleoptera: Coccinellidae]), a common green lacewing predator (Chrysoperla carnea Stephen [Neuroptera: Chrysopidae]), and a mirid predator (Macrolophus caliginosus[Wagner][Hemiptera: Miridae]) were independently made in three vegetable crops (cabbage [Brassica oleracea var. capitata L.], cucumber [Cucumis sativus L.], and squash [Cucurbita pepo L.]) for the management of the sweetpotato whitefly. Approximately 1 million to 2.5 million larvae or nymphs of each predator were released in the vegetable crops during 20 weeks. Whitefly populations were reduced by ≈ 25%–45% during most of the season in each crop where each predator was released. The effect of each predator was similar on whitefly population reduction. Late in the season (October) when whitefly populations were low, generally no benefit was obtained from releasing the predators. Numbers of predators recovered during sampling in all crops were greatest for C. carnea, but this corresponded with the fact that more individuals of this predator were released than any other predator in the experiment. These results help define the utility of these natural enemies for managing B. tabaci in vegetable crops.

Augmentation and evaluation of a parasitoid, Encarsia inaron, and a predator, Clitostethus arcuatus, for biological control of the pomegranate whitefly, Siphoninus phillyreae

The aim of this study was to evaluate the biological control potential of Encarsia inaron (Walker) (Hymenoptera: Aphelinidae) and a predator Clitostethus arcuatus (Rossi) (Coleoptera: Coccinellidae) against the pomegranate whitefly, Siphoninus phillyreae (Haliday) (Homoptera: Aleyrodidae) on pomegranate (Punica granatum L.) by mass rearing and augmentative releases of these two natural enemies during a long-term field study in Egypt. A study was conducted to evaluate the biological control potential of this pest by augmentation with a parasitoid, En. inaron, and a predator, C. arcuatus. Both species were mass reared and monthly releases were made in fields of pomegranate during each of 11 consecutive years (1996–2006). About 1,155,000 En. inaron and 990,000 C. arcuatus were released in fields in Assuit governorate in Egypt on pomegranate which was naturally infested by S. phillyreae. Populations of the natural enemies and parasitism were much higher in field plots where releases were made compared with where no releases were made. The maximum rate of parasitism reached 93% (88% by En. inaron) in the field treatment where releases were made, while parasitism peaked at 36% where no releases were made. The population of En. inaron was significantly correlated with the population of whitefly during the field season. Additional parasitism was by natural infestation with Eretmocerus parasiphonini Evans and Abd-Rabou (Hyneoptera: Aphelinidae). Among all years, the maximum number of C. arcuatus ranged from 13 to 44 beetles per 100 leaves for the treatment, and there were more predators in the release plot than in the control plot. These observations enhance understanding of the usefulness of these natural enemies after augmentation in the field.

Population of the Sweetpotato Whitefly in Response to Different Rates of Three Sulfur-Containing Fertilizers on Ten Vegetable Crops

Whiteflies in the Bemisia complex are global pests on numerous horticultural crops. The effect of cultural practices on the population of the B-biotype sweetpotato whitefly, Bemisia tabaci (Gennadius), is only partly understood. A study was conducted to examine the effect of different rates of three common sulfur-containing fertilizers (ammonium sulfate, potassium sulfate, and superphosphate) on the population of B. tabaci in 10 vegetable crops. Three different rates were tested in the field for each fertilizer, but the specific rates were varied among crops to reflect the general use by growers in comparison with higher and lower rates. Egg, nymph, and adult whitefly counts were generally elevated with increased rates of ammonium sulfate or decreased with increasing rates of potassium sulfate. Conversely, field and laboratory data suggested a reduction in whitefly counts on cabbage and cucumber in response to increased rates of ammonium sulfate. However, whitefly populations within crops were generally the same regardless of rate of the superphosphate. Although each of the three fertilizers provides more than one essential nutrient, the individual role of sulfur, or any other nutrient, on the whitefly population was not identified. Nevertheless, the results from this study support that in certain sulfur-containing fertilizers, populations of the sweetpotato whitefly can be affected in several vegetable crops.

Infestation by Bemisia tabaci (Hemiptera: Aleyrodidae) and incidence of whitefly-transmitted viruses after the application of four biorational insecticides in some crops in Egypt

Bemisia tabaci (Gennadius) is a global insect pest that transmits many important plant viruses. A field study was conducted on infestation by B. tabaci and incidence of whitefly-transmitted viruses after the application of selected foliar and seed-treated biorational insecticides in seven vegetable and row crops in Egypt. Three foliar insecticides (Actara, Biofly and Neemix) and a treated check (Actellic) were assayed across three weeks on seedlings and mature plants, and two seed-treated insecticides (Actara and Gaucho) and a treated check (Aldicarb) were assayed on seedlings. All of the foliar insecticides led to 60–100% reductions in whitefly infestations in each crop. Biofly and Neemix were the least efficacious insecticides. Incidences of whitefly-transmitted viruses were reduced in each insecticide-treated plot with seedlings of four crops; however, no effect on virus incidence was observed in the experiment with mature plants. Crops of cucumber, eggplant, squash and tomato displayed symptoms characteristic of Cucumber vein yellowing virus, Squash leaf curl virus or Tomato yellow leaf curl virus; however, no symptoms of whitefly-transmitted viruses were observed in green bean, potato or sugar beet. The results show that several biorational insecticides may suppress whitefly populations in seedlings to delay whitefly-transmitted viruses in some vegetable crops in Egypt.

Parasitoids as a bioagent to eliminate the insecticides to control the main pests-infested economic crops

Hemipterous insects are one of the important pests that attack different economic plants. A study was conducted to evaluate the biological control potential of these pests by augmentation with parasitoids, such as Microterys flavus (Howard), Metaphycus lounsburyi Howard (Encyrtidae), Encarsia sophia (Girault and Dodd), Coccophagus scutellaris (Dalman), Aphytis melinus DeBach (Aphelinidae) and Aphidius ervi Haliday (Braconidae). All the species were mass reared and monthly releases were made in fields of citrus, olive, tomato, sugar cane, mango and squash during each of 11 consecutive years (1999–2009). About 5,830,000 individuals of M. flavus, M. lounsburyi, E. sophia, C. scutellaris, A. melinus and A. ervi were released in the fields of Gharbiya, Marsa Matrouh, Daqahlyia, Qena, Qalyubiya and Behira governorates in Egypt on citrus, olive, tomato, sugar cane, mango and squash which were naturally infested by Ceroplastes floridensis Comstock, Saissetia oleae (Olivier) (Coccidae), Bemisia tabaci (Gennadius) biotype Q (Aleyrodidae), Pulvinaria tenuivalvata (Newstead) (Coccidae), Aulacaspis tubercularis (Newstead) (Diaspididae) and Aphis craccivora Koch (Aphididae), respectively. Population of the parasitoids and parasitism increased in field plots where releases were made when compared with where no releases were made. The maximum rate of parasitism reached 61.4, 92.1, 45.7, 59, 91 and 55.2% in the field treatment where releases were made, while parasitism peaked at 8.2, 13.5, 6, 2, 16 and 17.5% where no releases were made. The populations of M. flavus, M. lounsburyi, E. sophia, C. scutellaris, A. melinus, A. ervi were significantly correlated with the populations of C. floridensis, S. oleae, B. tabaci, P. tenuivalvata, A. tubercularis and A. craccivora during the field seasons. Additional parasitism was caused by natural infestations of Metaphycus helvolus (Compere) and M. lounsburyi (Howard) (C. floridensis), Scutellista cyanea (Motschulsky) (S. oleae), Encarsia lutea (Masi) and Eretmocerus mundus (Mercet) (B. tabaci biotype Q), Encarsia citrina (Craw) (A. tubercularis) and Aphelinus demyaati Abd-Rabou (A. craccivora). These observations enhance the understanding of the usefulness of these parasitoids after augmentation in the field.