L. Garciatorres et al., MODELING THE ECONOMICS OF CONTROLLING NODDING BROOMRAPE (OROBANCHE CERNUA) IN SUNFLOWER (HELIANTHUS-ANNUUS), Weed science, 44(3), 1996, pp. 591-595
Field studies were conducted at nine locations in southern Spain durin
g 2 yr to develop models of nodding broomrape competition with sunflow
er and to establish economic thresholds, At each location, 30 to 35 sm
all plots, each consisting of three sunflower plants, were chosen at r
andom, The infection severity (BIS, no, of emerged broomrapes per sunf
lower plant) varied from 0 to 35. Plots were harvested at maturity to
assess several sunflower and broomrape population variables, The perce
nt sunflower yield reduction averaged over locations due to broomrape
was estimated by the equation: % SYR= 1.7 x BIS (r(2) = 0.92). Crop yi
eld loss per BIS unit increased with the expected yield and was estima
ted to be about 25, 50, and 75 kg ha(-1) for yields of 1000, 2000, and
3000 kg ha(-1), respectively. A consistent relationship could be esta
blished between broomrape-infected sunflower yield, crop and broomrape
biomass, and BIS parameters: SSYI = 0.2259 x PoBio/(1 + 0.0687 x BIS)
(r(2) = 0.7820). The BIS economic threshold was about 1.5 and 3.5 for
control treatment cost of $ 40 ha(-1) and potential yields of 2000 an
d 1000 kg ha(-1), respectively.