Broomrapes (Phelipanche spp. and Orobanche spp.) are holoparasitic plants that cause tremendous losses of agricultural crops worldwide. Broomrape control is extremely difficult and only amino acid biosynthesis-inhibiting herbicides present an acceptable control level. It is expected that broomrape resistance to these herbicides is not long in coming. Our objective was to develop a broomrape control system in tomato (Solanum lycopersicum L.) based on the plant growth regulator maleic hydrazide (MH). Petri-dish and polyethylene-bag system experiments revealed that MH has a slight inhibitory effect on Phelipanche aegyptiaca seed germination but is a potent inhibitor of the first stages of parasitism, namely attachment and the tubercle stage. MH phytotoxicity toward tomato and its P. aegyptiaca-control efficacy were tested in greenhouse experiments. MH was applied at 25, 50, 75, 150, 300, and 600 g a.i. ha-1 to tomato foliage grown in P. aegyptiaca-infested soil at 200 growing degree days (GDD) and again at 400 GDD. The treatments had no influence on tomato foliage or root dry weight. The total number of P. aegyptiaca attachments counted on the roots of the treated plants was significantly lower at 75 g a.i. ha-1 and also at higher MH rates. Phelipanche aegyptiaca biomass was close to zero at rates of 150, 300, and 600 g a.i. ha-1 MH. Field experiments were conducted to optimize the rate, timing and number of MH applications. Two application sequences gave superior results, both with five split applications applied at 100, 200, 400, 700, and 1000 GDD: (a) constant rate of 400 g a.i. ha-1; (b) first two applications at 270 g a.i. ha-1 and the next three applications at 540 g a.i. ha-1. Based on the results of this study, MH was registered for use in Israel in 2013 with the specified protocol and today, it is widely used by most Israeli tomato growers.

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.

The tomato mutant line HRT was obtained by ethyl methanesulfonate seed mutagenesis of the commercial tomato line M82. Greenhouse studies were conducted to determine whole-plant response to the imidazolinone herbicides imazamox, imazapic, and imazapyr; pyrithiobac-sodium (a herbicide from the pyrimidinylthiobenzoic acid group); and propoxycarbazone sodium (sulfonylaminocarbonyltriazolinone group). The mutant was highly resistant to imazamox, imazapic, and imazapyr, but did not differ from M82 in its response to the sulfonylurea herbicides Envoke (trifloxysulfuron), Monitor (sulfosulfuron), and Glean (chlorsulfuron). Equip (foramsulfuron), a sulfonylurea herbicide, was toxic to M82 but less so to HRT plants. Under field conditions, HRT showed high resistance to imazapic and imazapyr. The herbicides at a rate of 144 g ai ha−1did not cause any reduction in HRT plant vigor, development, or yield. Results of greenhouse and field experiments demonstrated high Egyptian broomrape–control efficacy with the imidazolinone herbicides imazapic and imazapyr. Two imazapic applications of 9.6 or 14.4 g ai ha−1and three applications of 4.8 g ai ha−1in pot experiments completely prevented appearance of broomrape shoots aboveground. Three and four applications of the same herbicides in the field at a rate of 12 or 24 g ai ha−1completely prevented shoot appearance without any yield losses. Single imazapic application as high as 144 g ai ha−1did not damage the plants or reduce HRT yield.

It is not clear why herbicides targeting aromatic and branched-chain amino acid biosynthesis successfully control broomrapes—obligate parasitic plants that obtain all of their nutritional requirements, including amino acids, from the host. Our objective was to reveal the mode of action of imazapic and glyphosate in controlling the broomrape Phelipanche aegyptiaca and clarify if this obligatory parasite has its own machinery for the amino acids biosynthesis. P. aegyptiaca callus was studied to exclude the indirect influence of the herbicides on the parasite through the host plant. Using HRT – tomato plants resistant to imidazolinone herbicides, it was shown that imazapic is translocated from the foliage of treated plants to broomrape attachments on its roots and controls the parasite. Both herbicides inhibited P. aegyptiaca callus growth and altered the free amino acid content. Blasting of Arabidopsis thaliana 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS) and acetolactate synthase (ALS) cDNA against the genomic DNA of P. aegyptiaca yielded a single copy of each homolog in the latter, with about 78 and 75% similarity, respectively, to A. thaliana counterparts at the protein level. We also show for the first time that both EPSPS and ALS are active in P. aegyptiaca callus and flowering shoots and are inhibited by glyphosate and imazapic, respectively. Thus leading to deficiency of those amino acids in the parasite tissues and ultimately, death of the parasite, indicating the ability of P. aegyptiaca to synthesize branched-chain and aromatic amino acids through the activity of ALS and EPSPS, respectively.

Broomrapes (Orobanche and Phelipanche species, Orobanchaceae) are obligate root parasites of dicotyledonous plants. This taxonomic group includes seven weedy parasites of agricultural crops that damage vegetables, sunflower (Helianthus annuus L.), and legumes. Processing-tomato (Solanum lycopersicum L.) fields in Israel have been recently found infested with a new broomrape, first identified as nodding broomrape (Orobanche cernua Loefl.) based on its host. However, its morphology resembled the closely related sunflower broomrape (Orobanche cumana Wallr.), an obligate parasite of sunflower. The new race (CUCE) parasitized sunflower, tomato, and tobacco (Nicotiana tabacum L.) in vitro, in a polyethylene bag system and in pots. Its seeds germinated in response to strigolactones (orobanchol, 5-deoxystrigol, 2′-epiorobanchol, and GR24) and dehydrocostus lactone (DCL), whereas O. cumana seeds responded only to DCL and GR24, and O. cernua only to strigolactones. Based on morphological similarities with O. cumana, shared molecular markers with O. cumana, ability to parasitize sunflower and respond to sunflower-germination stimulants, it was concluded that CUCE is a new race of O. cumana, with a host range expanding to Solanaceae crops. While being an important noxious weed of sunflower, this new O. cumana race is currently spreading and posing a threat to processing tomato in Israel. This finding is an alarming indication that broomrapes can shift host range and that similar new races of O. cumana could potentially appear in other countries.

Carrot is a high-value cash crop that is grown in Israel throughout the year. Egyptian broomrape is a chlorophyll-lacking, obligate, root holoparasite that parasitizes members of many botanical families, including the Apiaceae. At high infestation levels, Egyptian broomrape can cause total yield loss in carrot. A protocol has been developed for the control of Egyptian broomrape in carrot. Because carrots are grown in Israel under fall, winter, and spring conditions, information about the relations between the efficacy of control and temperature is important. Therefore, the objective of this study was to investigate the response of carrot and Egyptian broomrape to herbicides at different phenological stages under varying temperature regimes. This study was conducted under temperature-controlled conditions in a multiclimate greenhouse and in a net house. Applications of the imidazolinone herbicides imazapic and imazamox (each applied at 4.8 g ai ha−1) injured carrot plants and reduced yield and yield quality. Glyphosate effectively controlled Egyptian broomrape and did not negatively affect the carrot plants when applied three times at ≤ 108 g ae ha−1. High temperatures increased the carrot plants’ sensitivity to glyphosate. This study found that three applications of glyphosate at 108 g ae ha−1can prevent Egyptian broomrape damage without causing any damage to the carrot crop. Our results indicate that weather conditions can affect herbicide phytotoxicity in carrot. The highest temperature at the time of herbicide application corresponded to the strongest observed phytotoxic effect. To summarize, effective Egyptian broomrape control can be achieved by three sequential foliar applications of glyphosate (108 g ae ha−1), beginning during the early parasitism stage (i.e., small tubercles). Moreover, applying glyphosate on carrot at high temperature (i.e., 28/22 C day/night temperatures) can injure carrot plants and reduce control efficacy.

Cyperus rotundus (purple nutsedge) is considered one of the most noxious weeds affecting agricultural areas worldwide. With its fast growth rate, it competes with annual crops for water, minerals, light and space. It excretes allelopathic materials that impede crop development. Controlling this weed is difficult and is done mostly by manual weeding, cultivation and herbicides, with limited effectiveness. A method was developed for the control of C. rotundus. A machine penetrates the soil and rearranges it, so that the tubers are lifted to the upper soil layer, where they are left exposed to the hot summer climate, dehydrate and die. The method was tested in seven field experiments on various soil types. Two months after the experimental plots were irrigated, 70-100% weed control was observed. The machine's speed (at 1.2 or 1.8 km h À1 ) and the number of treatments (one, or two treatments a month apart) did not influence the level of weed control. The method has a very high potential to replace manual weeding and application of herbicides. Further work will test whether the treatment has a long-term effect or should be repeated every season.

Chickpea (Cicer arietinum L.) is an ancient crop, mentioned in the Bible and in the Jerusalem Talmud. In the last 60 years, chickpea cultivation and breeding have undergone great advances. Those in cultivation have involved mainly changing the sowing dates and developing disease management for Ascochyta blight. In the last 10 years, to increase sowing areas, effort has been invested in developing agrotechniques for immature green chickpea harvesting. Today, breeding efforts are focused mainly on producing erect and high-yielding cultivars that are resistant to Ascochyta blight and Fusarium wilt. Moreover, in the last decade, breeding programs for early flowering have been initiated in the south of Israel, in areas with terminal drought, as well as for resistance to herbicides and the broomrape Phelipanche aegyptiaca. Thanks to all of these efforts, today chickpea is the major pulse crop in Israel.