Abstract:The cotton mealybug, Phenacoccus solenopsis Tinsley (Hemiptera: Pseudococcidae) is a polyphagous sap sucking insect with a wide geographical and host range causing severe losses in economically important crops. This study represents the first record of P. solenopsis as a new insect attacking cotton plants (Gossypium barbadense var. Giza 86) in Kafr El-Sheikh governorate, Egypt. The insect was noticed on cotton plants for the first time during its growing season of 2014. The mealybug specimens were collected from infested cotton plants and identified as P. solenopsis. In an attempt to control this pest, eight toxic materials viz., imidacloprid, thiamethoxam, flonicamid, emamectin-benzoate, chlorpyrifos, methomyl, deltamethrin and mineral oil (KZ-oil), belonging to different chemical groups, were tested for their influence against P. solenopsis on cotton under field conditions. Methomyl, imidacloprid, thiamethoxam and chlorpyrifos showed the highest efficacy against P. solenopsis recording 92.3 to 80.4% reduction of the insect population. Flonicamid, emamectin-benzoate and KZ-oil failed to exhibit sufficient P. solenopsis control.

Cotton aphid, Aphis gossypii Glover (Homoptera: Aphididae) is considered a key pest of cotton in Egypt. Hence, field and laboratory studies were conducted at Sakha Agriculture Research Station, Egypt during seasons 2016 and 2017. Efficiency of seven insecticides i.e., flonicamid, imidacloprid, thiamethoxam, emamectin-benzoate, chlorpyrifos, methomyl and deltamethrin against A. gossypii in cotton fields were evaluated. Their side effects on the associated predators, soil fauna and plant defense enzymes also were studied. Flonicamid was the most effective against A. gossypii. The efficacy of imidacloprid and thiamethoxam did not differ significantly from that of chlorpyrifos and methomyl recording from 83.28-93.27% reduction in A. gossypii infestation. Flonicamid, emamectin-benzoate, imidacloprid and thiamethoxam were the least harmful to the associated predators causing less than 50% mortality, while the others were highly toxic. Flonicamid exhibited the highest degree of safety to the soil micro-arthropods, followed by emamectin-benzoate, methomyl and deltamethrin. In contrast, chlorpyrifos and imidacloprid were the most toxic to the soil microarthropods. The conventional insecticides (chlorpyrifos, methomyl and deltamethrin) increased the activity of catalase and peroxidase causing physiological stress on the treated cotton plants, whereas the other tested insecticides recorded decreases in catalase and peroxidase activities inducing the plant defense response. Only imidacloprid and thiamethoxam increased the activity of polyphenol oxidase. Emamectin-benzoate and deltamethrin decreased the total soluble protein content, while the others tested insecticides caused increases in this criterion comparing to the control.

Two natural insect enemies, Chrysoperla carnea (Stephens) and Trichogramma evanescens (Westwood) and one insecticide, Profenofos, were assessed against the cotton leafworm, Spodoptera littoralis (Boisd.) under laboratory conditions. The first, second and third larval instars of C. carnea consumed 35.53±7.82, 35.82± 3.21 and 701.75± 135.6 eggs of S. littoralis, respectively. The second and third instar larvae consumed 166±39.1 and 729.91± 120.50 larvae of S. littoralis. The feeding capacity of second larval instar of C. carnea on eggs and larvae of S. littoralis differed significantly. T. evanescens parasitism was 71.05%, also the longevity of females and females percentage were 3.19 days and 39.00%, respectively. Oleander leaves, Nerium oleander infested with S. littoralis eggs were treated by dipping in 5 concentrations of profenofos, and LC50, LC90 were 39.19 and 639.681 ppm after 4 days from treatment. Moreover,The results showed that eggs mortality percentage were 43.19, 67.19, 75.20, 85.20 and 85.61% as a result of profenofos application with different concentrations 37.5, 75, 150, 300 and 600 ppm, respectively, compared with those of untreated eggs, (16.66%). This study reveals the importance of mass-rearing of biological control programs of C. carnea and T. evanescens to be successfully used in control of S. littoralis, and thus, the use of insecticides could be minimized or avoided.