ASSESSMENT OF PERFORMANCE LOSSES CAUSED BY DAMAGE OF Heliothis spp. IN COTTON

Abstract

The aim of this work was to estimate the economic damage caused by Heliothis spp. to the cotton fruiting organs, and on this basis to estimate the loss in yield. The work was carried out at the Campo Experimental "Balboa", Buga, Colombia. The experimental plots, 400 m², were planted with the variety Alcala 1517 BR 2. Both field and laboratory work was conducted. The real yield losses were estimated by comparing the yield obtained from plots completely protected during the whole growing period with selected insecticides with that from the check plots. The theoretical yield losses were calculated on the basis of the total larvae population during the growing period in the check plots, the average number of fruiting bodies consumed by a larva, and the plant stand per hectare. In the field, the yield losses due to the damage of Heliothis were of the magnitude of 61,63%. During the peak fruiting period, shed squares and bolis were collected to evaluate the Heliothis damage and the effectiveness of the insecticides treatments. As a result, it may be concluded that in cotton a total shedding of up to 71,43% of the potential crop occurs due both to the insect damage and to other causes, mainly of physiological nature. 2% -3% was due to Heliothis, the other 69% due to other causes. It was also observed that the majority of shed fruiting bodies were bolls in the early stages of development. By field and laboratory studies it was determined that a larva of Heliothis consumes during the entire larval period (18 to 21 days) an average of 6,00 to 6,26 fruiting bodies.