Hanan Eizenberg

Control of Orobanche crenata and Orobanche aegyptiaca in parsley

Abstract Parsley ( Petroselinum crispum ) is a host of the angiosperm root holoparasites Orobanche crenata and Orobanche aegyptiaca in the Mediterranean region and suffers heavy yield and quality losses. Eight field studies were performed to test the efficacy and selectivity of herbicides on Orobanche control in parsley. Initial experiments showed that the amino acid inhibiting herbicides imazapic and glyphosate did not affect the parsley crop and provided excellent Orobanche control. The efficacy of these herbicides was further tested by single and split post-emergence application at different geographical locations, in spring–summer (warm) and fall–winter (cold) growing seasons and on different Orobanche species. Finally the efficiency of tank mix and alternating application of these herbicides was studied. O. crenata and O. aegyptiaca were completely controlled by split foliar application of imazapic at 2.5– 5.0 g / ha or glyphosate 36– 72 g / ha , applied on 5–7 leaf parsley before the first cutting and on the young new growth after each cutting. At the low rates herbicides were parsley-safe, but higher rates caused slight crop damage. Split applications of low rates of the two herbicides as a tank mixture were safe to parsley and achieved effective Orobanche control. Herbicide mixtures and alternating applications are important in inhibiting or delaying the development of herbicide-resistance in weeds including parasitic plants. The findings of this study propose efficient, selective, low cost and easy to apply herbicides for control of Orobanche in parsley.

A predictive degree-days model for small broomrape (Orobanche minor) parasitism in red clover in Oregon

Abstract Weeds of the genus Orobanche parasitize many dicotyledonous species, causing severe damage to vegetable and field crops worldwide. In Oregon, the number of red clover fields contaminated with small broomrape has increased in recent years. Small broomrape parasitism in red clover is temperature related. In this study, the temperature-dependent relationship was developed into a predictive model based on growing degree-days (GDD) for small broomrape parasitism in red clover. The model was developed in greenhouse studies and validated in the field during three growing seasons. A strong relationship between GDD and parasite size allowed for the creation of a simple predictive model for tubercle number based on GDD. The proposed model is based on a temperature range realistic to western Oregon climatic conditions and predicts lag, log, and maximum phases for four parasitism sizes in relation to GDD. Small broomrape parasitism in red clover began at about 400 GDD, but red clover biomass accumulation was not affected by parasitism before 1,200 GDD. Small broomrape flower stalk emergence began at about 1,100 GDD. Field studies validated that GDD could be a predictive parameter for small broomrape parasitism and could be used to time detection surveys and herbicide applications. Nomenclature:u2003Small broomrape, Orobanche minor J. E. Smith. ORAMI; red clover, Trifolium pratense L. TRFPR.

Broomrape (Orobanche cumana) Control in Sunflower (Helianthus annuus) with Imazapic1

Abstract:u2009Field trials were conducted in 1997 and 1998 at two locations in Israel to evaluate the efficacy of imazapic applied postemergence (POST) to sunflower for broomrape control under irrigated and nonirrigated conditions. Two sequential treatments of imazapic at 1.5 followed by (FB) 3.0, 3.0 FB 4.5, or 4.5 FB 6.0 g ai/ha on sunflower plants 12 ± 3 and 55 ± 5 cm tall, respectively, reduced sunflower broomrape throughout the growing season under irrigated and nonirrigated conditions. Sunflower growth was not affected by imazapic treatments. It was confirmed, in accordance with an earlier report, that when sequential treatments of imazapic included an application at the sunflower inflorescence developmental stage, the herbicide decreased seed yield in proportion to the applied rate. Nomenclature: Imazapic; broomrape, Orobanche cumana Waller; sunflower, Helianthus annuus L. Additional index words: Parasitic weed, herbicide. Abbreviations: fb, followed by; POST, postemergence; PRE, preemergence.

Control of Orobanche aegyptiaca and O. ramosa in potato

Abstract Potato ( Solanum tuberosum ) is a susceptible host of the root holoparasites Orobanche aegyptiaca and Orobanche ramosa in the Mediterranean region, and suffers severe yield losses due to high levels of field infestations. Sulfonylurea and imidazolinone herbicides are selective acetolactate synthase-inhibiting herbicides that have been found effective for Orobanche control. In greenhouse and field experiments, O. aegyptiaca and O. ramosa were controlled in potato-infested soils by split foliar applications of low rates of the herbicides imazapic and rimsulfuron. Three doses of imazapic at 4.5xa0g/ha each, sprayed 2 weeks after crop emergence and re-applied at 2-week intervals, prevented Orobanche infestation. Although imazapic treatments increased crop vigor and potato yield, potato tuber quality was severely damaged in light sandy loam fields, where tubers were deformed pro rata to imazapic applied doses. A single application of 7.5xa0g/ha triasulfuron sprayed on potato foliage, severely damaged the crop. Three repeated applications of rimsulfuron at 12.5 or 25.0xa0g/ha at identical timing to imazapic, selectively controlled Orobanche and were found safe for potatoes as well as tuber quality. Rimsulfuron has approval for use on commercial crops of potato.

Movement of protein and macromolecules between host plants and the parasitic weed Phelipanche aegyptiaca Pers.

Little is known about the translocation of proteins and other macromolecules from a host plant to the parasitic weed Phelipanche spp. Long-distance movement of proteins between host and parasite was explored using transgenic tomato plants expressing green fluorescent protein (GFP) in their companion cells. We further used fluorescent probes of differing molecular weights to trace vascular continuity between the host plant and the parasite. Accumulation of GFP was observed in the central vascular bundle of leaves and in the root phloem of transgenic tomato plants expressing GFP under the regulation of AtSUC2 promoter. When transgenic tomato plants expressing GFP were parasitized with P. aegyptiaca, extensive GFP was translocated from the host phloem to the parasite phloem and accumulated in both Phelipanche tubercles and shoots. No movement of GFP to the parasite was observed when tobacco plants expressing GFP targeted to the ER were parasitized with P. aegyptiaca. Experiments using fluorescent probes of differing molecular weights to trace vascular continuity between the host plant and the parasite demonstrated that Phelipanche absorbs dextrans up to 70xa0kDa in size from the host and that this movement can be bi-directional. In the present study, we prove for the first time delivery of proteins from host to the parasitic weed P. aegyptiaca via phloem connections, providing information for developing parasite resistance strategies.

The relationship between temperature and small broomrape (Orobanche minor) parasitism in red clover (Trifolium pratense)

Abstract The root-parasitic broomrape species cause severe damage to field and vegetable crops worldwide. This study evaluated the relationship between small broomrape development and temperature with red clover as a host plant. Red clover plants were grown in soil artificially infested with small broomrape seed in temperature-controlled growth chambers. Parasite development was quantified at 48 different accumulated growing degree days (GDD). Small broomrape parasitism and temperature were strongly related. Small broomrape tubercle initiation was delayed by low temperature. Tubercle development initiated at about 750 GDD and peaked at about 1,100 GDD. Small broomrape biomass accumulation correlated with the increase in tubercle number over time. Parasitism stages were divided into lag, log, and maximum phases that were strongly related to GDD. Development of a predictive system for parasitism growth stage is needed to allow precise herbicide application for effective control before small broomrape shoot emergence. Nomenclature:u2003Small broomrape, Orobanche minor Sm. ORAMI; red clover, Trifolium pratense L. TRFPR.

Imazamox application timing for small broomrape (Orobanche minor) control in red clover

Abstract Broomrapes (Orobanche spp.) are chlorophyll-lacking root parasites of many dicotyledonous species and cause severe damage to vegetable and field crops from several botanic families such as Fabaceae, Solanaceae, Compositae, and Umbelliferae. In Oregon, small broomrape has been identified as a parasite of red clover. In Oregon field studies, small broomrape control was excellent when imazamox was applied postemergence to red clover but preemergence to small broomrape. Temperature is one of the main factors that affect broomrape development. The objective of this study was to optimize small broomrape chemical control in red clover based on growing degree days (GDD). The study was conducted in controlled temperature conditions. Red clover plants were grown in soil artificially infested with small broomrape seeds. Imazamox was applied at 800, 1,000, 1,200, and 1,400 GDD. There was no injury to red clover from any imazamox treatment at any of the application timings. Small broomrape shoot emergence was reduced where imazamox was applied compared to the untreated control. Early imazamox applications reduced small broomrape biomass more than later applications. Control was greatest when imazamox was applied at 20 g ai ha−1 at 1,000 GDD. This application controlled small broomrape for 800 GDD after initial treatment. However, season-long control would require an additional treatment. This model predicts the optimal timing and rate of imazamox application for small broomrape control in red clover. Nomenclature:u2003Imazamox; small broomrape, Orobanche minor J. E. Smith ORAMI; red clover, Trifolium pratense L. TRFPR.

Technologies for Smart Chemical Control of Broomrape (Orobanche spp. and Phelipanche spp.)

Abstract Broomrapes (Orobanche and Phelipanche spp.) are obligate root parasites that spend most of their life cycle in the soil subsurface, making them hard to detect. In these underground developmental stages, broomrapes are highly sensitive to herbicides, and therefore knowledge of the dynamics of their parasitism is essential to precisely apply herbicide for their control. To address these complexities, two approaches have been proposed: (1) estimating the temporal variation in parasitism dynamics and predicting broomrape parasitism on its host by thermal time; (2) characterizing the spatial variation in infestation within and between fields by using a geographical information system and a global positioning system. In addition, the use of molecular markers to identify broomrape infestation (species and amount) in the field can contribute to determining its spatial distribution, which can then be used for site-specific weed management. In this paper, we discuss how technology can be optimized for control of the root-parasitic broomrapes. Special attention is given to the development of integrative approaches. An example of a decision support system for the rational management of Egyptian broomrape in processing tomato is given. Nomenclature: Egyptian broomrape, Phelipanche aegyptiaca Pers. (syn. Orobanche aegyptiaca) ORAAE; tomato, Solanum lycopersicon L.

The Potential of Sulfosulfuron to Control Troublesome Weeds in Tomato1

There are few efficient and cost-effective methods for controlling weeds in processing tomatoes. Sulfosulfuron is a sulfonylurea herbicide developed for controlling weeds in wheat. In previous studies, we have demonstrated the efficacy of sulfosulfuron in selectively controlling Orobanche aegyptiaca in tomato. The objective of the present study was to elucidate the potential of sulfosulfuron to selectively control troublesome, nonparasitic weeds in tomato. In the greenhouse, sulfosulfuron efficacy at 37.5, 75.0, and 112.5 g ai/ha applied preplant incorporated (PPI), preemergence (PRE), and postemergence (POST) was tested. Sulfosulfuron when applied PPI and POST was highly selective in controlling weeds without causing injury to tomato. The weeds that were efficiently controlled, even at low rates of application, included purple nutsedge, black nightshade, mustard, pigweed, and bindweed. PRE application resulted in the most efficient weed control but was phytotoxic to tomato at high rates. Nomenclature: Sulfosulfuron; black nightshade, Solanum nigrum L. #3 SOLNI; field bindweed, Convolvulus arvensis L., # CONAR; purple nutsedge, Cyperus rotundus L. # CYPRO; redroot pigweed, Amaranthus retroflexus L. # AMARE; tomato, Lycopersicon esculentum Mill. # LYPES; wheat, Triticum aestivum L.; wild mustard, Sinapis arvensis L. # SINAR. Additional index words: Acetolactate synthase inhibitors, sulfonylurea herbicides, weed management. Abbreviations: ALS, acetolactate synthase; DAA, days after application; DAP, days after planting; POST, postemergence; PPI, preplant incorporated; PRE, preemergence.

Robust Methods for Measurement of Leaf-Cover Area and Biomass from Image Data

Leaf-cover area is a widely required plant development parameter for predictive models of weed growth and competition. Its assessment is performed either manually, which is labor intensive, or via visual inspection, which provides biased results. In contrast, digital image processing enables a high level of automation, thereby offering an attractive means for estimating vegetative leaf-cover area. Nonetheless, image-driven analysis is greatly affected by illumination conditions and camera position at the time of imaging and therefore may introduce bias into the analysis. Addressing both of these factors, this paper proposes an image-based model for leaf-cover area and biomass measurements. The proposed model transforms color images into an illumination-invariant representation, thus facilitating accurate leaf-cover detection under varying light conditions. To eliminate the need for fixed camera position, images are transformed into an object–space reference frame, enabling measurement in absolute metric units. Application of the proposed model shows stability in leaf-cover detection and measurement irrespective of camera position and external illumination conditions. When tested on purple nutsedge, one of the worlds most troublesome weeds, a linear relation between measured leaf-cover area and plant biomass was obtained regardless of plant developmental stage. Data on the expansion of purple nutsedge leaf-cover area is essential for modeling its spatial growth. The proposed model offers the possibility of acquiring reliable and accurate biological data from digital images without extensive photogrammetric or image-processing expertise. Nomenclature: Purple nutsedge, Cyperus rotundus L. CYPRO