Settling preferences of the whitefly vector Bemisia tabaci on infected plants varies with virus family and transmission mode

Virus infection may change not only the host‐plant phenotypic (morphological and physiological) characteristics, but can also modify the behavior of their insect vector in a mutualistic or rather antagonistic manner, to promote their spread to new hosts. Viruses differ in their modes of transmission and depend on vector behavior for successful spread. Here, we investigated the effects of the semi‐persistently transmitted Tomato chlorosis virus (ToCV, Crinivirus) and the persistent circulative Tomato severe rugose virus (ToSRV, Begomovirus) on alighting preferences and arrestment behavior of their whitefly vector Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae) Middle East Asia Minor 1 (MEAM1) on tomato plants (Solanum lycopersicum L. cv. Santa Clara, Solanaceae). The vector alighting preferences between infected and uninfected plants in choice assays were apparently influenced by the presence of ToCV and ToSRV in the whiteflies or by their previous exposure to infected plants. The observed changes in vector behavior do not seem to benefit the spread of ToCV: non‐viruliferous insects clearly preferred mock‐inoculated plants, whereas ToCV‐viruliferous insects landed on mock‐inoculated and ToCV‐infected plants, indicating a partial change in insect behavior – ToCV was able to directly affect the preference of its vector B. tabaci, but this change in insect behavior did not affect the virus spread because viruliferous insects landed on mock‐inoculated and infected plants indistinctly. In contrast, ToSRV‐viruliferous insects preferred to land on mock‐inoculated plants, a behavior that increases the probability of spread to new host plants. In the arresting behavior assay, the majority of the insects remained on mock‐inoculated plants when released on them. A greater number of insects moved toward mock‐inoculated plants when initially released on ToCV‐ or ToSRV‐infected plants, suggesting that these viruses may repel or reduce the nutritional quality of the host plants for B. tabaci MEAM1.     

Molecular Detection and Complete Genome Sequences of Tomato chlorosis virus Isolates from Infectious Outbreaks in China

Tomato chlorosis virus (ToCV) is a whitefly‐transmitted, phloem‐limited, bipartite Crinivirus. In 2012, severe interveinal symptoms characteristic of ToCV infections were observed in greenhouse tomato plants in the Shandong province of China. High levels of infestation by whiteflies (Bemisia tabaci), which transmit ToCV, were also observed on tomato plants in all the greenhouses investigated. The presence of ToCV was confirmed by specific RT‐PCR either in the sampled plants or in the whiteflies collected from the ventral surface of the leaves of diseased plants. The complete genomic nucleotide sequences (RNA1 and RNA2) of the Shandong isolate of ToCV (ToCV‐SDSG) were determined and analysed. ToCV‐SDSG RNA1 consisted of 8594 nucleotides encompassing four open reading frames (ORFs). ToCV‐SDSG RNA2 consisted of 8242 nucleotides encompassing nine ORFs. Phylogenetic analysis suggests that the Chinese ToCV‐SDSG isolate is most similar to the ToCV‐Florida isolate.     

Identification,comparison, and functional analysis of salivary phenol‐oxidizing enzymes in Bemisia tabaci B and Trialeurodes vaporariorum

The differences in the ability of the invading whitefly, Bemisia tabaci (Gennadius) (commonly known as biotype B and hereafter as B) and Trialeurodes vaporariorum (Westwood) (both Hemiptera: Aleyrodidae) to utilize salivary phenol‐oxidizing enzymes – polyphenol oxidase (PPO) and peroxidase (POD) to detoxify plant defensive phenolic compounds were explored. Polyphenol oxidase and POD were found in the saliva of both B and T. vaporariorum. For tomato colonies, the PPO and POD activities in the watery saliva of B were 2.27‐ and 1.34‐fold higher than those of T. vaporariorum. The PPO activities against specific phenolic compounds commonly found in plants were compared. The activities of those from B were significantly greater than those from T. vaporariorum. We also measured PPO activity in both species after they had fed on plants that were undamaged or had been previously damaged with either a plant pathogen [Phytophthora infestans (Mont.) de Bary (Peronosporales)] infection, mechanical damage, B infestation, or exogenous salicylic acid. For B, PPO activities in watery saliva increased 229, 184, 152, and 139% in response to the four treatments, whereas those of T. vaporariorum only increased 133, 119, 113, and 103%, respectively. Biotype B infestation significantly increased the total phenolic content of tomato leaves. Meanwhile, feeding on tomato infestation with B had no significant effect on the survival rate of B, but decreased the survival rate of T. vaporariorum significantly. These results suggest that B has stronger ability utilizing PPO to detoxify high concentrations of phenolics than T. vaporariorum, and this contributes to a significant advantage for B to hold high fitness on plants with induced resistance. Possible roles of salivary PPO in the competition between B and T. vaporariorum are discussed.     

Biotype and insecticide resistance status of Bemisia tabaci populations from Peninsular Malaysia

Bemisia tabaci, a resistance‐prone insect pest, is a cryptic species complex with important invasive biotypes such as B and Q. The biotype and resistance statuses of this pest in Malaysia remain unclear. This study assessed the biotype and resistance status of a number of contemporary populations of B. tabaci based on the mtCO1 marker and the dose‐response method, respectively. The Pahang (PHG) population was labelled as the Q biotype, while the remainder of the populations belonged to the Asia 1 biotype. A very low level of resistance for profenofos, cypermethrin, and imidacloprid was detected for all populations [resistance factor (RF) < 10]. Resistance to diafenthiuron ranged from very low to very high (RF > 100). All populations showed a very low level of resistance against pymetrozine except Q‐type PHG population, which exhibited a very high level of resistance. For most insecticides, the highest level of resistance was detected in the PHG population. The implications of these findings for better management of this noxious pest are discussed.     

Infection of tomato by Tomato Yellow Leaf Curl Virus alters the foraging behavior and parasitism of the parasitoid Encarsia formosa on Bemisia tabaci

Encarsia formosa Gahan is a solitary endoparasitoid that is commercially reared and released for augmentative biological control of whiteflies including Bemisia tabaci (Gennadius). Bemisia tabaci biotypes B and Q are two most invasive species that greatly reduce crop yields in China by feeding on plant sap and by transmitting Tomato Yellow Leaf Curl Virus (TYLCV). The effects of TYLCV infection of tomato on E. formosa foraging on B. tabaci B and Q are unknown. In Y-tube olfactometer assays in the present study, E. formosa significantly preferred TYLCV-infected tomato plants over TYLCV-free plants. The wasp females also significantly preferred TYLCV-infected tomato plants infested with 3rd-instar nymphs of B. tabaci biotype Q over TYLCV-free plants with biotype Q nymphs. However, no significant differences were observed when B. tabaci biotype B was infested on tomato plants. The oviposition bioassays confirmed that TYLCV infection on tomato plants resulted in the recruitment of parasitoids. These results indicate that TYLCV-infection of tomato increase the foraging of E. formosa on B. tabaci, as differs on the B and Q biotypes.     

Different effects of exogenous jasmonic acid on preference and performance of viruliferous Bemisia tabaci B and Q

The sweetpotato whitefly, Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae), B and Q biotypes have caused severe losses to crops and vegetables through virus transmission. Our previous studies showed that Q is more efficient than B in acquisition and transmission of tomato yellow leaf curl virus (TYLCV) and viruliferous Q is better equipped than B in counterattacking jasmonic acid (JA)‐related plant defense. To understand how plant‐mediated defensive responses involving JA affect insect vectors within a tritrophic framework of plants, insects, and viruses, we examined the effects of exogenous JA on preference and performance of non‐viruliferous and viruliferous B and Q on tomato plants (Solanum lycopersicum L., Solanaceae). Our results demonstrated a significantly lower fecundity, shorter longevity, shorter developmental time, and lower survival rate of whiteflies on JA‐treated than on control plants. In addition, viruliferous Q performed significantly better than B in fecundity, longevity, developmental time, and survival rate. When given a choice between JA‐treated and control tomato plants, viruliferous Q was not repelled to JA‐treated plants when the JA concentration was 0.01 and 0.1 mm , whereas others all preferred the untreated control plants. Exogenous JA increased the concentration and the composition of plant volatiles, such as α‐terpinene and β‐ocimene, which deterred whiteflies in a Y‐tube bioassay. It is worth noting that Q has a mutualistic relationship with TYLCV to counteract the host defenses. A better understanding of tritrophic interactions between plants, insects, and viruses will facilitate the development of sustainable management of this invasive global pest.     

Abundance of Bemisia tabaci Gennadius (Hemiptera: Aleyrodidae) and its parasitoids on vegetables and cassava plants in Burkina Faso (West Africa)

The whitefly Bemisia tabaci is a pest of many agricultural and ornamental crops worldwide and particularly in Africa. It is a complex of cryptic species, which is extremely polyphagous with hundreds of host plants identified around the world. Previous surveys in western Africa indicated the presence of two biotypes of the invasive MED species (MED‐Q1 and MED‐Q3) living in sympatry with the African species SSA and ASL. This situation constitutes one of the rare cases of local coexistence of various genetic entities within the B. tabaci complex. In order to study the dynamics of the distribution and abundance of genetic entities within this community and to identify potential factors that could contribute to coexistence, we sampled B. tabaci populations in Burkina Faso in 2015 and 2016 on various plants, and also their parasitoids. All four genetic entities were still recorded, indicating no exclusion of local species by the MED species. While B. tabaci individuals were found on 55 plant species belonging to eighteen (18) families showing the high polyphagy of this pest, some species/biotypes exhibited higher specificity. Two parasitoid species (Eretmocerus mundus and Encarsia vandrieschei) were also recorded with E. mundus being predominant in most localities and on most plants. Our data indicated that whitefly abundance, diversity, and rate of parasitism varied according to areas, plants, and years, but that parasitism rate was globally highly correlated with whitefly abundance suggesting density dependence. Our results also suggest dynamic variation in the local diversity of B. tabaci species/biotypes from 1 year to the other, specifically with MED‐Q1 and ASL species. This work provides relevant information on the nature of plant–B. tabaci‐parasitoid interactions in West Africa and identifies that coexistence might be stabilized by niche differentiation for some genetic entities. However, MED‐Q1 and ASL show extensive niche overlap, which could ultimately lead to competitive exclusion.     

Impacts of elevated CO2 on Bemisia tabaci infesting Bt cotton and its parasitoid Encarsia formosa

Atmospheric carbon dioxide concentration is expected to rise in the coming decades. Rising atmospheric CO₂ levels may alter plant‐insect‐parasitoid associations due to the indirect effects of CO₂ enrichment on phytochemicals important for herbivore and parasitoid nutrition. Tritrophic effects of elevated CO₂ on Bt cotton (GK‐12) and non‐transgenic (Simian‐3, or S3) cotton [Gossypium hirsutum L. (Malvaceae)], Bemisia tabaci (Gennadius) biotype B (Hemiptera: Aleyrodidae), and its parasitoid Encarsia formosa Gahan (Hymenoptera: Aphelinidae), were examined in open‐top chambers. Significantly, longer egg‐adult developmental duration and higher mortality of nymphs were observed under elevated CO₂ concentrations on both cotton cultivars during three successive generations. However, no significant differences were found in adult longevity, offspring sex ratio, and the number of eggs laid per female adult of B. tabaci fed on transgenic (GK‐12) or non‐transgenic cotton (S3) grown under elevated CO₂. Abundance of B. tabaci adults increased from 10 to 120 per plant and then decreased to 40 per plant through the growing season, but no significant differences in density occurred between CO₂ treatments and between cultivar treatments. Similarly, no significant differences were found in the developmental duration, parasitization rate, and adult emergence rate of E. formosa after parasitizing B. tabaci for three successive generations. Our results showed that the effects of transgenic Bt cotton did not significantly affect the development, survivorship, life span, or fecundity of B. tabaci and its parasitoids. Moreover, interactions between B. tabaci and E. formosa were not significantly affected by elevated CO₂. These results suggest that the biological control of B. tabaci by E. formosa would not be influenced by transgenic Bt cotton and/or elevated CO₂, indicating that the current risk management strategy regarding B. tabaci outbreaks and biocontrol by E. formosa will remain effective if the atmospheric CO₂ level continues to rise.     

Evaluation of Tomato Hybrids Carrying Ty‐1 and Ty‐2 Loci to Japanese Monopartite Begomovirus Species

Tobacco leaf curl Japan virus, Honeysuckle yellow vein mosaic virus and Tomato yellow leaf curl virus are three begomoviruses that infect tomato crops in Japan. Tomato infection by begomoviruses has increased in Japan after the development of a high level of resistance to certain insecticides in some populations of the vector B. tabaci biotypes ‘B and Q’. Ty‐1 and Ty‐2 homozygous tomato hybrids were evaluated for reaction to monopartite begomovirus species in Japan by Agrobacterium‐mediated inoculation. Test plants were evaluated by a disease assessment scale (DAS), varying from 1 = no symptoms to 4 = severe symptoms, and systemic infection was evaluated by polymerase chain reaction (PCR), using specific begomovirus primers for each virus. Ty‐1 hybrids showed tolerance to HYVMV and with a large number of plants being neither virus‐free nor symptom‐free. The response of Ty‐1 hybrids was also resistant to moderately resistant against TbLCJV. The response of Ty‐2 hybrids was resistant to highly resistant against the three monopartite begomoviruses, when compared with susceptible plants.     

The Complete Nucleotide Sequence of the RNA 1 of a Chinese Isolate of Tomato chlorosis virus

Interveinal leaf chlorosis, brittleness, limited necrotic flecking or bronzing developed on greenhouse‐grown tobacco and tomato plants at Nanjing Agricultural University from 2010 to 2013. A positive RT‐PCR using a pair of degenerate primers for Crinivirus confirmed the diseased plants were infected with Tomato chlorosis virus (ToCV). The complete RNA 1 genomic sequence of this ToCV isolate was determined; it comprises of 8596 nucleotides with four open reading frames. Phylogenetic analysis of ToCV isolates from diverse geographical regions categorized the ToCV isolates into two main groups. Group one consisted of Chinese, American‐Florida, Greek and Brazilian isolates, while Group two contained only the Spanish isolate. The first group had two subgroups, one of Chinese and American‐Florida isolates, while the other subgroup had Greek and Brazilian isolates. This is the first study of the complete nucleotide sequence of the RNA 1 of ToCV isolated from China.     

Effects of host,temperature and relative humidity on competitive displacement of two invasive Bemisia tabaci biotypes [Q and B]

Abstract Bemisia tabaci shifted unexpectedly in China from a predominance of B biotype to Q biotype during 2005–2008. This observation stimulated an interest in investigating whether environmental factors, including host, temperature and relative humidity (RH) could possibly explain the observed shift in biotypes distribution. Results indicated that all three parameters examined influenced biotype survivability. The percentage of B biotype, when reared together on pepper plants with the Q biotype, decreased significantly from 66.7% in the founder population, to 13.6% and 3.7% in the first and second generations, respectively. When the B (founder at 66.7%) and Q (founder at 33.3%) biotypes were reared together on eggplant alone, or on pepper‐plus‐eggplant combination, the population size of the B biotype either remained constant, or increased somewhat in the first and second generations. On eggplant, the effects of RH and temperature on the competitiveness between the Q and B biotypes (3 pairs of Q and 6 pairs of B) were not significant.     

Does a multi‐plant diet benefit a polyphagous herbivore? A case study with Bemisia tabaci

Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae) is a highly polyphagous herbivore. This research was conducted to compare the development of B. tabaci reared in a multi‐plant treatment (polyculture) with those in single‐plant treatments (monocultures). Adult B. tabaci females fed on a mixture of tomato, cabbage, cotton, cucumber, and kidney bean survived longer and laid more eggs than those fed exclusively on one of these plant species. Egg numbers per plant laid in the polyculture treatment were positively correlated with those laid on the same plant species in the monoculture treatments, and egg numbers per plant laid on tomato, cotton, and cucumber in the polyculture were significantly higher than those laid on the same plants in the monocultures. Concentrations of total protein and trehalose in B. tabaci were not significantly different after 7 days of feeding in the respective treatments, but activities of superoxide dismutases (SOD) and alkaline phosphatase (AKP) of B. tabaci in polyculture were lower than those in monoculture. Conversely, activities of trehalase, sucrase, and amylase in B. tabaci kept in polyculture were higher than those of insects from the monoculture. In each of the monoculture treatments, there was a negative correlation between AKP in B. tabaci and oviposition, and also between AKP and amylase. SOD and sucrase activities in B. tabaci were positively correlated with polyphenol oxidase (PPO) and peroxidase (POD) activities in plants. In the plants damaged by whiteflies in the polyculture treatment, activities of SOD in cucumber, PPO in cotton and kidney bean, and POD in tomato and cucumber were lower than those in the monoculture treatments, whereas SOD in cabbage and catalase (CAT) in tomato in the polyculture treatment were higher than those in the monoculture treatments.     

Temporal Dynamics of Tomato Severe Rugose Virus and Bemisia tabaci in Tomato Fields in São Paulo,Brazil

Temporal progress of a begomovirus disease in tomato fields and the abundance of its whitefly vector, Bemisia tabaci biotype B, were evaluated during three consecutive tomato plantings in the municipality of Sumaré, state of São Paulo, Brazil, in 2006 and 2007. The incidence of symptomatic plants and the number of adult whiteflies were weekly monitored on experimental plots randomly chosen in tomato commercial fields. Tomato severe rugose virus (ToSRV) was identified as the causal agent of the disease, and its relationships with other Brazilian begomoviruses was confirmed by partial and complete nucleotide sequencing of the viral genome. The disease temporal progress was analysed by fitting different models to disease incidence. The monomolecular model showed the best fit, which is consistent with a predominant role of primary spread in the epidemiology of ToSRV. A higher number of adult whiteflies were observed at the borders of the plots, also suggesting primary spread of ToSRV from external sources of inoculum, which might be represented by weeds and volunteer tomato‐infected plants. In Brazil, since 2004, there is a legislative measure that mandates, for some regions of processing tomato plantings, a 2‐month crop‐free period during the year. Based on our results, we suggest the extension of this measure to all tomato‐producing regions, including fresh market tomato. We also suggest that growers emphasize the elimination of old plants from harvested fields that can serve as virus reservoirs several weeks prior to new plantings and weeds nearby the fields to limit the primary spread of ToSRV.     

Differences in host selection and performance between B and Q putative species of Bemisia tabaci on three host plants

B and Q are two putative species of the Bemisia tabaci complex (Hemiptera: Aleyrodidae), and are among the most invasive and destructive pests of crops and horticultural plants worldwide. In China, Q predominates and is displacing B. Although researchers have proposed that the higher capacity of Q to utilize host plants plays an important role in its replacement of B, there are few relevant field surveys and experimental studies. The difference in host assessment between B and Q in multiple‐choice rather than in no‐choice situations may be essential to understanding the displacement. Here, we compared settling and oviposition preferences, and adult and nymph performance, for the putative species B and Q of the B. tabaci complex on three common host species: poinsettia [Euphorbia pulcherrima Wild. ex Klotsch (Euphorbiaceae)], cotton [Gossypium hirsutum L. (Malvaceae)], and cabbage [Brassica oleracea L. (Brassicaceae)]. Although the preferred hosts for settling and oviposition were the same as those that supported maximum fitness (adult longevity, fecundity, and nymph survivorship), these hosts differed between B and Q. When given a choice, B preferred to settle and oviposit on cabbage over poinsettia and cotton, whereas Q preferred to settle and oviposit on poinsettia and cotton over cabbage. In a no‐choice experiment, adult longevity, fecundity, and nymphal survival for B were greater on cabbage than on poinsettia and cotton, but the opposite was true for Q.     

Genetic identification of members of the Bemisia tabaci cryptic species complex from South Africa reveals native and introduced haplotypes

The whitefly Bemisia tabaci cryptic species complex contains some important agricultural pest and virus vectors. Members of the complex have become serious pests in South Africa (SA) because of their feeding habit and their ability to transmit begomovirus species. Despite their economic importance, studies on the biology and distribution of B. tabaci in SA are limited. To this end, a survey was made to investigate the diversity and distribution of B. tabaci cryptic species in eight geographical locations (provinces) in SA, between 2002 and 2009, using the mitochondrial cytochrome oxidase I (mtCOI) sequences. Phylogenetic analysis revealed the presence of members from two endemic sub‐Saharan Africa (SSAF) subclades coexisting with two introduced putative species. The SSAF‐1 subclade includes cassava host‐adapted B. tabaci populations, whereas the whiteflies collected from cassava and non‐cassava hosts formed a distinct subclade, referred to as SSAF‐5, and represent a new subclade among previously recognized southern Africa clades. Two introduced cryptic species, belonging to the Mediterranean and Middle East–Asia minor 1 clades, were identified and include the B and Q types. The B type showed the widest distribution, being present in five of the eight provinces explored in SA, infesting several host plants and predominating over the indigenous haplotypes. This is the first report of the occurrence of the exotic Q type in SA alongside the more widely distributed B type. Furthermore, mtCOI PCR‐RFLP was developed for the SA context to allow rapid discrimination between the B, Q and SSAF putative species. The capacity to manage pests and disease effectively relies on knowledge of the identity of the agents causing the damage. Therefore, this study contributes to the understanding of South African B. tabaci species diversity, information needed for the development of knowledge‐based disease management practices.     

At least two indigenous species of the Bemisia tabaci complex are present in Brazil

Bemisia tabaci is one of the most important global agricultural insect pests, being a vector of emerging plant viruses such as begomoviruses and criniviruses that cause serious problems in many countries. Although knowledge of the genetic diversity of B. tabaci populations is important for controlling this pest and understanding viral epidemics, limited information is available on this pest in Brazil. A survey was conducted in different locations of São Paulo and Mato Grosso states, and the phylogenetic relationships of B. tabaci individuals from 43 populations sampled from different hosts were analysed based on partial mitochondrial cytochrome oxidase 1 gene (mtCOI) sequences. According to the recently proposed classification of the B. tabaci complex, which employs the 3.5% mtCOI sequence divergence threshold for species demarcation, most of the specimens collected were found to belong to the Middle East‐Asia Minor 1 species, which includes the invasive populations of the commonly known B biotype, within the Africa/Middle East/Asia Minor high‐level group. Three specimens collected from Solanun gilo and Ipomoea sp. were grouped together and could be classified in the New World species that includes the commonly known A biotype. However, six specimens collected from Euphorbia heterophylla, Xanthium cavanillesii and Glycine maxima could not be classified into any of the 28 previously proposed species, although according to the 11% mtCOI sequence divergence threshold, they belong to the New World high‐level group. These specimens were classified into a new recently proposed species named New World 2 that includes populations from Argentina. Middle East‐Asia Minor 1, New World and New World 2 were differentiated by RFLP analysis of the mtCOI gene using TaqI enzyme. Taq I analysis in silico also differentiates these from Mediterranean species, thus making this method a convenient tool to determine population dynamics, especially critical for monitoring the presence of this exotic pest in Brazil.     

Tomato yellow leaf curl virus infection of tomato does not affect the performance of the Q and ZHJ2 biotypes of the viral vector Bemisia tabaci

Abstract To better understand the etiology of begomovirus epidemics in regions under invasion we need to know how indigenous and invasive whitefly vectors respond to virus infection. We investigated both direct and indirect effects of infection with Tomato yellow leaf curl virus (TYLCV) on the performance of the invasive Q biotype and the indigenous Asian ZHJ2 biotype of whitefly Bemisia tabaci. The Q biotype performed better than the ZHJ2 biotype on either uninfected or virus‐infected tomato plants. However, virus‐infection of host plants did not, or only marginally affected, the performance of either biotype of whiteflies in terms of fecundity, longevity, survival, development and population increase. Likewise, association of the vectors with TYLCV did not affect fecundity and longevity of the Q or ZHJ2 biotypes on cotton, a non‐host of TYLCV. These results indicate that the alien Q biotype whitefly, but not the indigenous ZHJ2 biotype, is likely to become the major vector of TYLCV in the field and facilitate virus epidemics.     

Diadegma insulare development is altered by Plutella xylostella reared on water‐stressed host plants

Natural enemies of herbivores function in a multitrophic context, and their performance is directly or indirectly influenced by herbivores and their host plants. Very little is known about tritrophic interactions between host plants, pests and their parasitoids, particularly when the host plants are under any stress. Herbivores and their natural enemies’ response to plants under stress are diverse and variable. Therefore, in this study we investigated how diamondback moth, Plutella xylostella (L.), reared on water‐stressed host plants (Brassica napus L. and Sinapis alba L.) influenced the development of its larval parasitoid, Diadegma insulare (Cresson). No significant differences were observed in development of P. xylostella when reared on water‐stressed host plants. However, all results indicated that water stress had a strong effect on developmental parameters of D. insulare. Development of D. insulare was delayed when the parasitoid fed on P. xylostella, reared on stressed host plants. Egg to adult development of D. insulare was faster on non‐stressed B. napus than non‐stressed S. alba followed by stressed B. napus and S. alba. Female parasitoids were heavier on non‐stressed host plants than stressed counterparts. Furthermore, the parasitoid lived significantly longer on stressed B. napus. However, body size was not affected by water treatment. Most host plant parameters measured were significantly lower for water‐stressed than non‐stressed treatments. Results suggest that development of this important and effective P. xylostella parasitoid was influenced by both water stress and host plant species.