Keywords : associated
Evaluation of two methods, the direct method and sweeping– net for sampling of some arthropoda insects associated with foliage of some cotton varieties
ANBAR JOURNAL OF AGRICULTURAL SCIENCES,
2011, Volume 9, Issue 1, Pages 207-214
Afield experiment was conducted at the field of the College of Agriculture, Abu-Ghraib, Baghdad to evaluate the efficacy of two sampling methods, the direct method and the sweeping – net , to estimate the population density of some insects and mites associated with the foliage of three cotton varieties (Abu-Ghraib , Daes and Ashur). A sampling program on a regular basis has been developed during the season. Results showed clear differences in the types and numbers of insects collected in every method way. The main species collected by the two methods were: the whitefly, Bemesia tabaci, leaf hopper, Asymmetrasca decedents and cotton thrips, Thrips tabaci. There were no significant differences in the numbers of the whitefly for the three varieties by the direct method which amounted to (3.89, 4.39, 4.09) individual/ 5 leaves respectively, while there were significant differences when using the sweep– net, in which the highest numbers was recorded on Daes (6.05/ 5 leaves), which/ differed significantly from the numbers on the varieties Ashur and Abu-Ghraib (11.7 and 13.00)/ 5 leaves respectively. There were no significant differences in the numbers of leaf hopper, A. decedents and cotton thrips T. tabaci colleted in every way for the three varieties. The leaf hopper numbers ranged between 15.39 to 16.19/ 5 leaves by the direct method and 1.80 to 1.39/ 10 sweep-net, while thrips numbers ranged between 1.29 to 1.39/ 5 leaves and, 1.19 to 1.42/ 10 sweep– net. In addition to the main insects species collected above, other species collected by the sweep– net alone included: the cotton seed bug, Oxycarenus hyalipennis, bud and flower bug, Crenotides pallidus (Rambur). Among insect predators collected both methods on all varieties the ladybird, Coccinella septumpuntata L., the ladybird with 11– spots, C. undecimpuntata L., numbers of the last species have been higher on Abu– Ghraib variety (1.32/ 5 leaves), compared 0.89 and 0.99/ 5 leaves for the varieties Daes and Ashur respectively. The anthocorid bug, Orius albidipennis (Reuter) numbers were higher on the variety Ashur (1.06/ 5 leaves), compared with (0.79, 0.89)/ 5 leaves on the varieties Abu-Ghraib and Daes, respectively. Numbers of syrphid fly was relatively similar on all varieties and ranged between (2.18– 2.39)/ 5 leaves. The, aphid lion, Chrysoperla sp. and Scymnus sp. Were collected in low numbers from the varieties by the sweeping– net. The possibility of benefit from the use of the two sampling methods for detecting the presence of insect pests and their predators and to assess vital numerical density in cotton fields also discussed.
ANBAR JOURNAL OF AGRICULTURAL SCIENCES,
2007, Volume 5, Issue 2, Pages 124-134
Field experiement was carried out during winter season of 2001/2002 and 2002/2003 at the Field Crops Station (formerly IPA Agricultural Research) to investigate Brassica napus L. and associated weeds to newly introduced herbicides and determine their selectivity in canola for approval and registration in Iraq. The experiement included the following treatments:- Preemergence application of clomazone (48% q.i) at 0.24 and 0.3 lit. product/ha, preplant– application of napropamide (50% q.i) at 2 and 2.8 lit. product/ha, postemergence application of pyridate (45% q.i) at 2 kg product/ha, preplant application of trifluralin (44.5% q.i) at 2.4 lit. product/ha. Hand – weeded and weedy – check treatments were also included for comparison Randomized Complete Block Design was followed to arrange the treatments.
Results revealed the efficacy of clomazone, napropamide and pyridate in controlling broadleaf and reducing weed densities to an averages of 6 – 12.6 plants/m2 compared to 58 plant/m2 at the weedy plots. Grass densities were decreased to 0 – 12 plants/m2 compared to 12 plants/m2 for the untreated weedy check. Pyridate showed no activity on grasses. The reduction in weed densities resulted in low weeds dry weight: 9 - 38 gm/m2 for the herbicide – treated plots compared to 193 gm / m2 of the weedy – check. Clomazone caused significant injury on canola foliage which was reflected by discoloration (bleaching) and plant stunting. Plant height was reduced by both rates of clomazone to 49 – 52 cm compared to 98 cm for the hand – weeded plots. Variable effects of herbicides were observed on canola yield components and this was reflected on final seed yield wheras clomazone caused noticeable reduction in seed yield: 634 – 940 kg/ha, although with its high efficacy on weeds. Napropamide increased seeds yield to 1304 kg/ha at 2.8 liters/ha application rate and was as close as to that of the hand – weeded plot seeds yield. Long – season weeds competition with canola caused high percent of reduction; 60 %, the yield was reduced from 1368 kg/ha of the hand – weeded plots to 540 kg/ha of the weedy – plots. In 2002 - 2003, the same trend of effects of herbicidal weed control treatments on weeds was found and clomazone caused 40 – 50 % injury on canola foliage.
From these results, clomazone can not be recommend and approved to use in canola due to its noticeable injury on canola while napropamide can be applied preplant in this crop at 2.8 liters/ha to control broadleaf and grassy weeds and pyridate at 2 kg/ha can be used postemergence for broadleaf weeds control under irrigated regions of Iraq.