Egyptian Broomrape (Phelipanche aegyptiaca) Management in Carrot under Field Conditions

Abstract

The chlorophyll-lacking holoparasite Egyptian broomrape is a major threat for many field crops in Israel. In carrot, a high-value crop that is grown year round in Israel, heavy infestation with broomrape can cause severe damage and even total yield loss. The objective of this study was to determine, under field conditions, selective herbicides that would effectively control Egyptian broomrape without damaging the carrots. Ten field experiments were performed between the years 2010 and 2013. The acetolactate synthase inhibitor herbicides imazapic and imazamox caused deformation of carrot taproots at low doses, and significantly reduced yield amount and quality. Glyphosate was found to be the safest herbicide for broomrape management in carrot. Carrot selectivity and broomrape control efficacy were examined with three sequential applications of nine glyphosate doses. A nonlinear log-logistic curve described the response of noninfested carrot taproot biomass to glyphosate. No significant reduction in taproot biomass was observed when glyphosate was applied at up to 149 g ae ha−1. When glyphosate was applied in an Egyptian broomrape-infested carrot field, a hormetic effect was observed, perhaps due to Egyptian broomrape control. A two-parameter exponential decay curve described the broomrape response to glyphosate. Three sequential foliar applications of glyphosate, at 108 g ha−1, completely controlled Egyptian broomrape. Our results demonstrate that glyphosate applied sequentially at a low dose on Egyptian broomrape-infested carrot can control this parasitic weed.

Thermal Time Model for Egyptian Broomrape (Phelipanche aegyptiaca) Parasitism Dynamics in Carrot (Daucus carota L.): Field Validation

“…A previous study has shown that control of P. aegyptiaca growing on carrots can be achieved by application of low doses of glyphosate to the carrot foliage (Jacobsohn and Kelman, 1980). The findings of that study were confirmed by recent studies in Israel that demonstrated effective glyphosate control of P. aegyptiaca parasitism at different infestation levels under different climate regimes (Cochavi et al, 2015, 2016). …”

“…Therefore, accurate prediction of initiation of P. aegyptiaca attachment is a prerequisite for optimal herbicide application (Cochavi et al, 2016). However, field experiments have shown that the best results are obtained using sequential herbicide application (Cochavi et al, 2015), and it is therefore essential to have in hand a parasitism dynamics model for accurately predicting the timing of herbicide application. Previously developed models are not suitable, as they pertain to short-term crops grown over the summer or greenhouse crops grown mostly under moderately high temperature regimes.…”

“…The beta-function model, unlike the linear model, gives an accurate prediction of the first establishment of P. aegyptiaca on carrot roots, due to its ability to deal with the parasite development at supra-optimal temperatures. However, it is known from previous research that beneficial P. aegyptiaca management in the field requires at least three sequential applications of glyphosate, not only at the first attachment but also at later stages (Cochavi et al, 2015). Therefore, although the BTSG model contains more parameters than the beta function model and can predict the P. aegyptiaca first attachment at the same level, its ability to predict more accurately the total parasitism process is superior, as is needed for optimal herbicide application in the field.…”

Recent research progress in combatting root parasitic weeds

“…The model was also effective for predicting the entire parasitism dynamics, not only for predicting the first attachment, and could be used for precise temporal chemical management of P. aegyptiaca in carrot (Daucus carota) fields [200]. Three sequential foliar applications of glyphosate at 108 g/ha completely controlled P. aegyptiaca in carrot fields [201,202]. Moreover, applying glyphosate to carrot plants at high temperature injured them and reduced the P. aegyptiaca control efficacy [202].…”

Secondary Effects of Glyphosate Action in Phelipanche aegyptiaca: Inhibition of Solute Transport from the Host Plant to the Parasite

“…Despite the considerable amount of work that has been devoted to P. aegyptiaca , this parasitic plant still poses a challenge in weed management, particularly because only a few herbicides are available for its control (Eizenberg et al, 2013 ). Among these, the non-selective herbicide glyphosate can efficiently control P. aegyptiaca (Joel et al, 1995 ), even in low doses (Jacobsohn and Kelman, 1980 ; Cochavi et al, 2015 ). Glyphosate inhibits the enzyme 5-enolpyruvyl shikimate-3-phosphate synthase (EPSPS; EC 2.5.1.19) (Steinrücken and Amrhein, 1980 ), a key enzyme in the shikimate pathway and in the aromatic amino acids (AAA) biosynthesis pathway.…”