بررسی ترجیح میزبانی سوسک شاخدار Oryctes elegans (Coleoptera: Scarabaeidae) روی ارقام مختلف نخل خرما در استان خوزستان

Larvae and adults of Oryctes elegans Prell. (Coleoptera: Scarabaeidae) feed on under new offshoots, crown leaves, fruit stalks, trunks, and even the heart of the palm causing to break of the leaves, spikes, and sometimes even the tree's death. Considering the expansion of this pest and its significant damage in recent years, it is necessary to investigate the various behavioral aspects of O. elegans for better management. Knowing the reaction of different date cultivars to the attack and feeding of this beetle helps to prevent the spread and development of sensitive cultivars and to follow pest control operations more sensitively. The larvae were collected from the grove, and reared at a temperature of 30±1°C, relative humidity of 50±10%, and 24 hours of darkness to found a colony. The host preference of second and third instars of O. elegans including no-choice and choice experiments was investigated on five cultivars of Estamaran, Barhi, Zahedi, Deiri, and Gantar. In the non-choice test, each of the cultivars was examined separately. A piece of two to five grams of the midrib of each cultivar alone was placed for larvae in a 10×15×10 cm cylindrical plastic container for 24 hours. Each cultivar had 10 replications, and the midrib pieces were weighed before and after the experiment. In the choice test, the conditions were similar to the non-choice test, with the difference that a two to five grams piece of the midrib of all cultivars was given to the larvae at the same time for 24 hours. In this test, the number of replications was 15 for the second instar larvae. The mean consumption rate (%) was calculated in each test and for different instars of larvae, and the comparison was done with Tukey's test. The results of the non-choice test showed that there was no significant difference between cultivars in the second instar larvae (F(4,49)=2.07; P<0.1052), but in the third instar, the difference was significant (F(4,49) = 4.49; P<0.0048) therefore the highest rate of consumption (%) were on Estamaran (57.97±5.37), Barhi (53.20±12.68) and Deiri (36.75±5.28) and the lowest rate (%) were on Gantar (20.56±5.25) and Zahedi (26.22±4.33) cultivars. But when all cultivars were available to the larvae, the difference was significant in both instars (the second instar: F(4,74) = 4.51; P<0.0031 and the third instar: F(4,49)=25.32; P<0.0001), Therefore in both larval instars, the highest rate of consumption (%) was on Barhi (16.30±1.44; 45.50±5.12), Deiri (14.55±2.90; 39.15±5.41) and Estamaran (14.45±2.34; 31.80±4.42) and the lowest rate (%) on Gantar (5.90±0.89; 4.85±0.93) and Zahedi (9.95±2.17; 5.25±0.68) cultivars. Based on the results of both tests, it seems that Gantar and Zahedi cultivars are less affected and preferred by the O. elegans compared to the Barhi, Deiri, and Estamaran cultivars.