Field evaluation of indigenous predacious insect, Chrysoperla carnea (Steph.) (Neuroptera: Chrysopidae), fitness in controlling aphids and whiteflies in two vegetable crops

The green lacewing, Chrysoperla carnea (Stephens) (Neuroptera: Chrysopidae), is a generalist predator. Adults feed only on nectar, pollen, and aphid honeydew, but its larvae are active predators. C. carnea occurs in a wide range of habitats (Henn and Weinzierl, 1990). It is considered as an effective generalist predator of most species of soft bodied insect pests, especially aphids, whiteflies, thrips, coccids, and mealy bugs (McEwen et al., 2001). C. carnea had been recorded in different regions in Saudi Arabia as indigenous species, and it was molecularly identified by different mitochondrial genes (Sayed and Amer, 2015). Biological characteristics of the predator on the aphid species, Aphis fabae Scop., as a natural prey, and on Ephestia kuehniella (Zeller) eggs, as an alternative prey, were studied (Alghamdi and Sayed, 2017).

C. carnea has the adaptability to different environmental conditions and food diversity. It has a high searching capacity and a higher potential to prey on about 200 aphid species and more than 80 species of other insect pests (Tauber et al., 2000). C. carnea has been widely used for biological control of aphids and other insect pests because of its polyphagous habits and compatibility with selected chemical insecticides, microbial agents, and amenability for mass rearing (Uddin et al., 2005). It has been mass-reared and marketed commercially in the world, especially in North America and Europe (Tauber et al., 2000). Eggs of E. kuehniella are one of the most factitious preys for mass production of chrysopids’ species because this food ensures quick growth and development, high survival rates, and higher fecundity (Specty et al., 2003).

Biological aphid control on sweet peppers (Capsicum annuum L.) includes applications of generalist predators and parasitoids (De Backer et al., 2015). The melon aphid, Aphis gossypii Glover (Homoptera: Aphididae), is one of the most common aphid species on sweet pepper plants (Sanchez et al., 2011). This pest species has a variation in its biological parameters and reproduction on different sweet pepper cultivars (Alizadeh et al., 2016).

Squash plants (Cucurbita pepo L.) are attacked by many insect pest species, especially A. gossypii (Nyoike and Liburd, 2010). Damage may be caused directly by sucking plants’ juice or indirectly by transmitting plant viruses (Wu et al., 2010).

The whitefly, Bemisia tabaci (Gennadius) (Homoptera: Aleyrodidae), is one of the key pest species of sweet pepper and squash plants that causes direct damage by sucking the plant sap and indirect damage by transmitting of virus diseases (Banihashemi et al., 2017).

The present study aimed to evaluate the efficacy of releasing the indigenous C. carnea larvae for controlling A. gossypii and B. tabaci infesting sweet pepper and squash plants in open field trials.

According to the General Authority of Meteorology and Environmental Protection (KSA), the minimum temperature during the experiment period ranged between 19 and 23 °C, while the maximum temperature ranged between 33 and 35 °C. The average humidity was 31% at daytime and 36% at night.

Aphid densities did not differ significantly, 10 days after the first release, between the releasing rates of five second instar larvae (88.27 and 4.4 nymphs/squash and pepper leaves, respectively) and the ten one (75.6 and 2.47 nymphs/squash and pepper leaves, respectively) (Tables 1 and 3). Meanwhile, whitefly densities, at this period, were significantly different between the releasing rates of five larvae (10.87 and 2.47 nymphs/squash and pepper leaves, respectively) and the ten one (6.2 and 0.6 nymphs/squash and pepper leaves, respectively) (Tables 2 and 4). Moreover, the whitefly reduction on squash plants in this period was significantly different between both releasing rates (Table 1), while the reduction of aphid counts was insignificant (Table 2). This reduction reached more than 90% after the third release of ten larvae per plant for both pests and increased to 100% in the case of the whitefly only after six releases. The maximum reduction in the releasing rate of five larvae/plant was achieved after six releases (74% for aphid and 64% for whitefly). Abrams and Matsuda (1996) indicated that sharing of two prey species to a predator may affect each other’s densities positively because an increase in the populations of one pest species resulting in decreased predation on the other pest species. However, Messelink et al. (2008) stated that whitefly control of each of two predators in the absence of the thrips was not sufficient, while whitefly densities in the presence of thrips were reduced significantly.

On sweet pepper plants, the reduction in densities of both pests and after 10 days of the first release were significantly different (Tables 3 and 4). The aphid reduction reached about 90 and 97% after the second release of five and ten larvae per plant, respectively. A 100% reduction was achieved after four releases with five larvae/plant and three releases with ten larvae/plant (Table 3). The whitefly reductions seemed to be similar to those of aphids (Table 4). El-Arnaouty et al. (2000) obtained the best results from M. persicae control by releasing C. carnea second instar larvae on green pepper plants under greenhouse conditions, while the lower aphid suppression was achieved after releasing the combination of eggs and second instar larvae or eggs only of the predator.

The present findings indicate that the releasing rate of five larvae/pepper plant was sufficient for obtaining a good suppression of both B. tabaci and A. gossypii. Meanwhile, the releasing rate of ten larvae/squash plant was found adequate for better suppression of both pests. This result coincides with Zaki et al. (1999) who found that C. carnea induced highly significant reduction of A. gossypii and B. tabaci at different releasing rates on various vegetable crops.

Moreover, researchers such as Easterbrook et al. (2006) indicated that C. carnea is effective in open field than in protected crops and found that the aphid, Chaetosiphon fragaefolii infestation, was significantly reduced at the releasing rate of eight larvae/strawberry plant in open field experiments but did not give a significant reduction in aphids under protected crops, even at a releasing rate of 25 larvae/plant.

In conclusion, the obtained data showed that the aphid and whitefly populations on sweet pepper and squash plants, in open fields, were successfully suppressed by the releases of C. carnea. Control of two sap-sucking pests under investigation differed according to the releasing rate of the predator, at five and ten larvae per pepper and squash plant, respectively. The predatory action could be characterized as both curative and preventive.