Abubakar Muhammad Raza

Tritrophic interactions between parasitoids and cereal aphids are mediated by nitrogen fertilizer

Host plant nutritional quality can directly and indirectly affect the third trophic levels. The aphid–parasitoid relationship provides an ideal system to investigate tritrophic interactions (as the parasitoids are completely dependent for their development upon their hosts) and assess the bottom up forces operating at different concentrations of nitrogen applications. The effects of varying nitrogen fertilizer on the performance of Aphidius colemani (V.) reared on Sitobion avenae (F.) and Aphidius rhopalosiphi (D.) reared on Rhopalosiphum padi (L.) were measured. Parasitism and percent emergence of parasitoids were positively affected by nitrogen fertilizer treatments while developmental duration (egg, larval, and pupal stages) was not affected by increasing nitrogen inputs. In males and females of both parasitoid species, adult longevity increased with the increasing nitrogen fertilizer. Hind tibia length and mummy weight of both parasitoid species increased with nitrogen fertilizer concentrations, as a result of larger aphids. This study showed that nitrogen application to the soil can have important consequences for aboveground multitrophic interactions.

Botanicals, selective insecticides, and predators to control Diaphorina citri (Hemiptera: Liviidae) in citrus orchards

The Asian citrus psyllid (ACP) Diaphorina citri Kuwayama vectors pathogens that cause huanglongbing (HLB) or citrus greening devastating and economically important disease present in most citrus growing regions. Young citrus shoots are required for psyllid reproduction and development. During winter citrus trees produce little or no new growth. Overwintering adults reproduce in spring on newly emerging shoots also attractive to other pests and beneficial insects. Botanicals and relatively selective insecticides could help to conserve beneficial insects and reduce pest resistance to insecticides. Sprays of Azadirachtin (Neem), Tropane (Datura), Spirotetramat, Spinetoram, and broad‐spectrum Imidacloprid were evaluated to control ACP in spring and summer on 10‐year‐old “Kinow” Citrus reticulata Blanco trees producing new growth. Psyllid populations were high averaging 5–9 nymphs or adults per sample before treatment application. Nymphs or adults were significantly reduced to 0.5–1.5 per sample in all treatments for 3 weeks, average 61%–83% reduction. No significant reduction in ladybeetles Adalia bipunctata, Aneglei scardoni, Cheilomenes sexmaculata, and Coccinella septempunctata was observed. Syrphids, spiders and green lacewings were reduced in treated trees except with Tropane. Studies are warranted to assess impact of these predators on ACP and interaction with insecticides. Observed reduction in ACP populations may not be enough considering its reproductive potential and role in the spread of HLB. Follow‐up sprays may be required to achieve additional suppression using rotations of different insecticides.

Seasonal abundance of greater wax moths (Galleria mellonella L.) in hives of western honey bees (Apis mellifera L.) correlates with minimum and maximum ambient temperature

The greater wax moth, Galleria mellonella L., is a natural pest of western honey bee (Apis mellifera L.) colonies. They can overwhelm weakened honey bee colonies and occasionally cause significant losses to the beekeeping industry. In this study, we determined the seasonal abundance (No. moth larvae/hive) of G. mellonela larvae in hives of honey bees located in district Sargodha, Punjab, Pakistan. Our data showed that the maximum moth abundance occurred during the regional dearth period, i.e. May–November. The peak abundance (14.8 ± 3.9 moth larvae/hive) occurred in August. A multiple correlation analysis was used to estimate the association between explanatory variables (multiple weather factors) and the abundance of wax moth larvae in hives, and a stepwise regression analysis was used to find the best explanatory variable for high abundance. All abiotic factors were correlated with the seasonal abundance of greater wax moth larvae but minimum and maximum temperature correlated with moth abundance more than did any other variable tested. The results of the study can be used when designing an integrated pest management strategy for the greater wax moth by allowing one to focus treatment strategies to time of year the moths are most abundant.

Biochemical studies on the amylase of Mango Mealybug (Drosicha stebbingi Green)

Summary Mealybug (Drosicha stebbingi Green) is voracious pest of the mango orchards. It causes heavy quality losses and low production of mango fruit (Luhanga & Gwinner 1993). The research was conducted to control the pest. Isolation, purification and characterization of amylase from mango mealybug were performed. Amylolytic activity was 365U/ml in crude homogenate of D. stebbingi whereas in acetone precipitation sample activity was 680 U/ml. The optimum pH and temperature for amylase activity was 6.4 and 50-60 oC, respectively. However, amylase activity was maximum at 3% of substrate (starch) concentration. Enzymatic activity was inhibited by Pb