Predatory potential of Chrysoperla carnea and Cryptolaemus montrouzieri larvae on different stages of the mealybug, Phenacoccus solenopsis: a threat to cotton in South Asia

Larvae of Cryptolaemus montrouzieri (Coleoptera: Coccinellidae) Prioritize Secretion of Protective Wax Over Daily Consumption and Growth

In holometabolous insects, the immature or larval stage is characterized by a high rate of food consumption. The nutrients obtained from which are directed towards the maintenance of metabolism, growth, pupation, and metamorphosis. However, when resources are scarce, the lack thereof can affect the growth rate and compromise the metamorphosis and formation of adults. Do increased energy expenditures yield outcomes similar to those resulting from restricted food intake during the larval stage? We hypothesized that removing the wax layer from the larvae of the ladybird Cryptolaemus montrouzieri Mulsant, 1850 would result in increased energy expenditure, which can compromise both larval growth and adult size. We compared the development time, feeding rate, and adult size of larvae with an intact wax layer, and those with constantly removed wax layers. We found that the production of the wax layer was continuous. Unlike the waxed larvae, the larvae of C. montrouzieri extended their development time in response to energy depletion through wax removal. The total number of mealybugs consumed by waxless larvae was higher than the total number consumed by waxed larvae; however, the daily consumption of waxless larvae was lower than that of waxed larvae. Furthermore, the adults of waxless larvae were smaller than those whose larvae had intact wax layers. This suggests that the cost associated with wax layer secretion is a pivotal factor in larval growth. Removing this layer does not get compensated by increased larval feeding or extended development time.

Moroccan entomopathogenic nematodes as potential biocontrol agents against Dactylopius opuntiae (Hemiptera: Dactylopiidae)

Dactylopius opuntiae (Cockerell) (Hemiptera: Dactylopiidae) or prickly pear cochineal, is the most damaging pest on cactus species with heavy economic losses worldwide. The efficacy of two Moroccan EPN isolates; Steinernema feltiae (Filipjev) (Rhabditida: Steinernematidae) and Heterorhabditis bacteriophora (Poinar) (Rhabditida: Heterorhabditidae) (applied at 25, 50, and 75 IJs cm⁻²) against D. opuntiae nymphs and young females were evaluated under both laboratory bioassays and field conditions. Results showed that S. feltiae was more effective, causing higher mortality of nymphs and adult females (98.8% and 97.5%, respectively) after 8 days of exposure, resulting in an LT₅₀ value of 5.9 days (nymph) and 6.0 days (young female). While, H. bacteriophora had lower mortalities (83.8% for nymph and 81.3% for adult females). For the cochineal nymphs and adult females, no significant difference was observed among S. feltiae at 25, 50, and 75 IJs cm⁻², and the positive control, d-limonene applied at 0.5 g/L which was used due to its high effectiveness against nymphs and females of D. opuntiae. In the field experiment, d-limonene at 0.5 g/L and S. feltiae applied at 75 IJs cm⁻² were effective in reducing nymph and adult female populations by 85.3–93.9% at 12 days of post exposure period. To our knowledge, this work is the first report on the use of EPNs to control D. opuntiae. Thus, in addition to d-limonene, both Moroccan EPN isolates S. feltiae, and H. bacteriophora could be used as part of the integrated pest management strategy against D. opuntiae. Many factors such as temperature can affect the establishment and effectiveness of EPNs under field conditions. Therefore, additional studies under field conditions are needed.

Temperature Dependence for Survival, Development, and Reproduction of the Cactus Cochineal Dactylopius opuntiae (Cockerell)

Simple Summary

Cactus is an important drought-tolerant crop that has very various beneficial uses. In Morocco, cactus is a perfectly appropriate crop for land rehabilitation in the arid and semi-arid regions. With little investment, it can produce important resources for human and animal nutrition and generate adequate revenues for farmers. Unfortunately, the sustainability of this extremely resilient ecosystem has become seriously threatened by the appearance of Dactylopius opuntiae (Hemiptera: Dactylopiidae). This cochineal which is specific to cacti, was introduced in Morocco in 2014. The aim of this study was to evaluate the effect of temperature on life cycle parameters of D. opuntiae at 20, 23, 26, 32, and 40 ± 1 °C, 65 ± 5% RH, and a photoperiod of 12L:8D. Temperatures ranging from 26 °C to 32 °C were appropriate for the survival, development, and reproduction of the scale insect. Parthenogenesis in females was not observed during our study. This study also showed that D. opuntiae females required a higher thermal constant (769.23 D°) than males (357.14 D°) to grow to the mature adult stage.

Abstract

The effect of temperature on Dactylopius opuntiae (Cockerell) life cycle parameters was evaluated at 20, 23, 26, 32, and 40 ± 1 °C, 65 ± 5% RH, and a photoperiod of 12 L:8 D. Temperatures ranging from 26 °C to 32 °C were suitable for survival, development, and reproduction of D. opuntiae. The total developmental time of females ranged from 94.23 d (20 °C) to 43.55 d (40 °C). The average development time of males from egg to death ranged from 26.97 days at 32 °C to 50.75 days at 20 °C. The probability that a newly laid egg would survive to the adult stage was highest at 26 °C and 32 °C (44–60%). The parthenogenesis in females was not observed during our study. The longest oviposition period was observed when the cochineal was reared at 32 °C (17.97 days), and the highest fecundity was observed at 32 °C (355.29 egg/female). The highest proportion of females (0.80) was observed at 40 °C. According to the age-stage-two-sex life table, the highest value of the intrinsic rate of natural increase (r_m) was recorded at 32 °C. The lower developmental thresholds for the total pre-adult female and male and adult female and male stages, were 10.15, 12.21, 10.54, and 21.04 °C, respectively. Dactylopius opuntiae females needed a higher thermal constant (769.23 D°) than males (357.14 D°) to achieve their development and reach the mature adult stage. These findings will be useful for the development of an integrated pest management strategy for D. opuntiae.

Biology, ecology, and management of cotton mealybug Phenacoccus solenopsis Tinsley (Hemiptera: Pseudococcidae)

The cotton mealybug Phenacoccus solenopsis Tinsley (Hemiptera: Pseudococcidae), is a highly invasive and harmful pest. It causes considerable loss of cotton crops in China, India and Pakistan. Little is known about its bionomics since it was first recorded in Pakistan and India in 2005. Rapid spread of this pest worldwide has accelerated research on its biology, ecology and management. The P. solenopsis has a short life cycle, and optimal temperatures lead to an increase in the number of generations per year, which is a serious threat to cotton crop production. Cotton mealybug is native to the USA, although it has now spread to >43 countries. Insecticidal control is the primary and dominant practice for this pest, and its resistance to commonly used insecticides is increasing. Biocontrol agents have strong potential for the management of nymphal instar stages. We read >250 articles related to our review title and finally reviewed recent advances in the understanding of P. solenopsis biology, ecology and control approaches, aiming to highlight integrated and biological management practices of this pest. © 2021 Society of Chemical Industry.

Intraguild Interactions between the Mealybug Predators Cryptolaemus montrouzieri and Chrysoperla carnea

Simple Summary

The ladybird Cryptolaemus montrouzieri is a widely commercialized biological control agent of mealybugs. The green lacewing Chrysoperla carnea is mainly released for aphid control, but also attacks mealybugs. Both species have shown potential to control various economically important species of mealybug pests of greenhouse crops. As these predators may be simultaneously present in a crop, the risk of negative interactions between both predators was evaluated in this laboratory study. Individuals of different life stages of either predator were placed together in petri dish arenas and predation was recorded. Attacks between individuals of both species were frequently observed, with lacewing larvae being the dominant predators in most combinations. When mealybug nymphs or lepidopteran eggs were added to the arena, the incidence of attacks between the predators was greatly diminished. The relevance of these observations for the use of the predators in the biological control of greenhouse pests is discussed.

Abstract

The ladybird Cryptolaemus montrouzieri and the green lacewing Chrysoperla carnea have shown potential for use in augmentative biological control of mealybug pests in greenhouse crops. In the context of combining these predators within an integrated pest management system, the risk of negative intraguild interactions between both predators was evaluated in a laboratory setting. Different life stages of either predator were confronted in petri dish arenas containing a Ficus benjamina leaf, and after 24 h the incidence and direction of intraguild predation (IGP) was recorded for each combination. The effect of adding Planococcus citri nymphs or Ephestia kuehniella eggs as extraguild prey on the level of IGP was also studied. IGP was frequently observed between the two predator species and was asymmetrical in favour of C. carnea in most cases. The presence of extraguild prey reduced the number of IGP events between the predators to a similar extent. The relevance of the observed intraguild interactions for the combined use of these predators in protected cultivation is discussed.

Odonate Nymphs: Generalist Predators and Their Potential in the Management of Dengue Mosquito, Aedes aegypti (Diptera: Culicidae)

BACKGROUND

Dengue is amongst the most serious mosquito-borne infectious disease with hot spots in tropical and subtropical parts of the world. Unfortunately, no licensed vaccine for the disease is currently available in medicine markets. The only option available is the management of dengue vector mosquito, Aedes aegypti (Diptera: Culicidae).

METHOD

Predatory potential of five odonate nymphs namely Anax parthenope, Bradinopyga geminate, Ischnura forcipata, Rhinocypha quadrimaculata, and Orthetrum sabina were evaluated against the 4(th) instar larvae of the dengue vector mosquito, Aedes aegypti, under laboratory conditions. The consumption of the mosquito larvae was evaluated at three water volume levels viz., 1 liter, 2 liter and 3 liter.

RESULTS

The number of Ae. aegypti larvae consumed varied significantly among the five species, and at different levels of water volume (P< 0.01). However, the interaction between odonate nymphs and the water volumes was statistically non-significant (P> 0.05). Ischnura forcipata consumed the highest number of Ae. aegypti larvae (n=56) followed by A. parthenope (n=47) and B. geminate (n=46). The number of larvae consumed was decreased with increasing search area or water volume, and the highest predation was observed at 1-liter water volume.

CONCLUSION

The odonate nymphs could be a good source of biological agents for the management of the mosquitoes at larval stages.

Effects of transgenic Cry1Ac + CpTI cotton on non-target mealybug pest Ferrisia virgata and its predator Cryptolaemus montrouzieri

Recently, several invasive mealybugs (Hemiptera: Pseudococcidae) have rapidly spread to Asia and have become a serious threat to the production of cotton including transgenic cotton. Thus far, studies have mainly focused on the effects of mealybugs on non-transgenic cotton, without fully considering their effects on transgenic cotton and trophic interactions. Therefore, investigating the potential effects of mealybugs on transgenic cotton and their key natural enemies is vitally important. A first study on the effects of transgenic cotton on a non-target mealybug, Ferrisia virgata (Cockerell) (Hemiptera: Pseudococcidae) was performed by comparing its development, survival and body weight on transgenic cotton leaves expressing Cry1Ac (Bt toxin) + CpTI (Cowpea Trypsin Inhibitor) with those on its near-isogenic non-transgenic line. Furthermore, the development, survival, body weight, fecundity, adult longevity and feeding preference of the mealybug predator Cryptolaemus montrouzieri Mulsant (Coleoptera: Coccinellidae) was assessed when fed F. virgata maintained on transgenic cotton. In order to investigate potential transfer of Cry1Ac and CpTI proteins via the food chain, protein levels in cotton leaves, mealybugs and ladybirds were quantified. Experimental results showed that F. virgata could infest this bivalent transgenic cotton. No significant differences were observed in the physiological parameters of the predator C. montrouzieri offered F. virgata reared on transgenic cotton or its near-isogenic line. Cry1Ac and CpTI proteins were detected in transgenic cotton leaves, but no detectable levels of both proteins were present in the mealybug or its predator when reared on transgenic cotton leaves. Our bioassays indicated that transgenic cotton poses a negligible risk to the predatory coccinellid C. montrouzieri via its prey, the mealybug F. virgata.