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• 8

  Dec
  Prevention of phytotoxic effect of fungicides applied via drenching for powdery mildew control on pepper

  Plant Protection, Vegetables

  by Shimon Pivonia, Ph.D.

  13
  תחום או ענף הגה"צ; ירקות

  תאריך עדכון 14/3/2012

  Prevention of phytotoxic effect of fungicides applied via drenching for powdery mildew control on pepper
  Shimon Pivonia, Rachel Levite, Ami Maduel – Central and Northern Arava R&D
  E-mail address for correspondence: ShimonP@arava.co.il

  Abstract
  Powdery mildew is the main canopy disease of pepper crops in the Arava. This disease is caused by the fungus Leveillula taurica, which develops inside the leaf tissue and destroys that tissue. The mycelia and spores that emerge from the leaf provide the characteristic white dusting that looks similar to flour. (Translator’s note: The Hebrew term for “powdery mildew” is derived from the word for “flour”.) The disease appears every growing season. Pepper is planted in the Arava beginning in late July and powdery mildew appears in the fields when the temperature drops. There is a 6 to 8 week period during which conditions for powdery mildew development are generally optimal. After this period, the rate of powdery mildew development decreases.
  In experiments carried out at the R&D Authority, it was found that the disease could be prevented and/or its severity could be significantly reduced throughout the season if disease development could be inhibited during this critical period. Similarly, it was found that a single drench application of fungicide could protect pepper plants against powdery mildew for 3 to 4 weeks. Two properly timed fungicide drenches can protect the plant from powdery mildew throughout the period of optimal disease development. The use of this method eliminates the need for many sprays and improves control efficacy. As the use of this technique has spread to the majority of pepper plots in the Arava, we have observed some incidents of phytotoxicity caused by azoxystrobin, which is found in Amistar, as well as Extra granules. In this work, we evaluated the significance of this damage in terms of yield in a cultivar that is particularly sensitive to phytotoxicity, as well as ways to minimize this damage.
  We examined the Ramiro-type pepper cv. Madonna, which is sensitive to drench-applied material. We observed leaves yellowing and dropping off of the plants and a decreased rate of growth that persisted for about a month after the last drench. In terms of yield, we observed a delay in harvests throughout March, but there was no effect on overall yield, fruit size or fruit quality. Distributing the same total amount of fungicide across a greater number of application treatments (with a lower application rate) did not decrease the signs of phytotoxicity on the plants. In an accompanying experiment in line 4833 grown using a Spanish trellis system, we observed signs of phytotoxicity at the shoot meristems following the application of azoxystrobin. However, in that experiment, the fungicide treatment did not affect the rate of yield accumulation or overall yield. It is possible that the relatively high level of phytotoxicity observed in cv. Madonna is related to the use of a Dutch trellising system, in which the majority of the material reaches one shoot meristem of each plant as opposed to multiple meristems in the Spanish trellising system.
  To date, we have not observed any phytotoxicity problems for the triazoles, such as Hosen. The other products permitted for use as drenches to control powdery mildew of pepper are Amistar and similar fungicides, which are strobilurins and Extra granules, which contain a triazole (Atemi) and a strobilurin (azoxystrobin). We recommend that growers who apply fungicide drenches continue to apply two drenches each season with chemicals from different families, except perhaps in particularly sensitive cultivars. This will significantly decrease the risk of fungicide resistance, ensuring the usefulness of this method for many years to come.

  Acknowledgement
  We thank the Plant Board for their financial support of this work.

  שפה English
  מלות מפתח Capsicum
  מחבר Shimon Pivonia, Rachel Levite, Ami Maduel
  שנה 2011
  שייכות yzvieli
  תאריך יצירה 14/3/2012
  תאריך עדכון 14/3/2012
• 8

  Apr
  Integrated control of Monosporascus cannonballus, the causal agent of sudden wilt of melons

  Plant Protection, Vegetables

  by Shimon Pivonia, Ph.D.

  16
  תחום או ענף הגה"צ; ירקות

  תאריך עדכון 14/3/2012

  Integrated control of Monosporascus cannonballus, the causal agent of sudden wilt of melons
  Shimon Pivonia, Rachel Levite, Ami Maduel – Central and Northern Arava R&D
  E-mail address for correspondence: ShimonP@arava.co.il

  Abstract
  Melon is an important crop in the Arava. The main soilborne disease affecting melon in the Arava and elsewhere in southern Israel is the sudden wilting caused by the fungus Monosporascus cannonballus. To date, there is still no substitute for methyl bromide for controlling this disease in spring melon crops. The goal of this research is the development of methods for controlling Monosporascus in the Arava without methyl bromide or any negative yield effects. Experiments concerning ways to inhibit this disease were conducted over four years (2006-2010) at the Zohar Experimental Station in Sodom Valley. There were two cropping seasons each year, a short fall season during which melon was grown in the open field and a long spring season during which melon was grown in walk-in tunnels. We also evaluated ways to control weeds in spring melon crops. We evaluated the effects of a combination of methods, disinfection in the fall, destruction of the remains of the fall crop with Edigan (metham sodium) and the application of fungicide during the season, on the morbidity of the plants and crop yield over three years in the spring and fall seasons.
  We found that the most influential factor was the use of fungicide. The use of a combination of methods led to increased yield in spring melon. The combination of control methods did not contribute to increased yields in fall melon crops. Applying mycorrhizae to the plants led to fewer plants dying in the fall crop and helped increase yield in comparison with the control treatment. However, in the spring crop, the use of mycorrhizae did not have any positive effects on plant morbidity or yield. The use of the herbicide Goal (oxyflurofen) before the spring melon was transplanted had no negative yield effect. We found that the use of black/silver (lower/upper sides) plastic to help control weeds in the spring crop may have a negative effect on yield. If methyl bromide can not be used in spring melon in the Arava, we recommend the following: a soil disinfection treatment in the fall + application of fungicide during the fall season + destruction of the remains of the fall crop with metham sodium + application of fungicides during the spring season. Of all of these treatments, treatment with fungicide is the most significant. A combination of the application of methyl bromide before the spring season and the application of fungicide during the season provides significantly increased yields.

  Acknowledgement
  We thank the office of the Chief Scientist of the Ministry of Agriculture for funding research project no. 603-0243-08.

  שפה English
  מחבר Shimon Pivonia, Rachel Levite, Ami Maduel
  שנה 2011
  שייכות yzvieli
  תאריך יצירה 14/3/2012
  תאריך עדכון 14/3/2012
• 8

  Apr
  Control of Pythium in pepper during the summer in the Arava

  Plant Protection, Vegetables

  by Shimon Pivonia, Ph.D.

  הגה"צ; ירקות

  תאריך עדכון 14/3/2012

  Control of Pythium in pepper during the summer in the Arava
  Shimon Pivonia, Rachel Levite – Central and Northern Arava R&D
  E-mail address for correspondence: ShimonP@arava.co.il

  Abstract
  Pepper crops in the Arava are attacked by a number of different Pythium species. Early in the season, the plant can be negatively affected by Pythium species that develop best at particularly high temperatures, particularly Pythium aphanidermatum. Pythium can kill plants at the germination stage. Later, when conditions are mild, like those found in a nursery, the plants are not sensitive to Pythium. When young plants are transplanted into a field they are exposed to the temperatures prevailing in the Arava during August, which makes them once again sensitive to Pythium infection. Plants that have been infected by Pythium lose their turgor during the day and recover in the evening and this can continue until temperatures drop. Some of the infected plants are not able to recover and die. The yields of Pythium-infected plants are expected to be significantly less than those of healthy plants.
  The goal of this work is the evaluation of appropriate materials for the control of Pythium in the field during the summer. Within the framework of this work, which was conducted at the Yair Experimental Station during the 2010/11 season, a method was developed for simulating the death of plants in the field in a controlled growth chamber. This allowed the evaluation of a wide range of treatments. None of the biological treatments and plant-resistance treatments that were evaluated provided effective control of Pythium damage in pepper. Of the fungicides evaluated in the growth chamber, Ridomil (metalaxyl + mancozeb) and Tachigaren (hymexazol) were the most effective and these materials were also evaluated under field conditions. In the field, the most effective treatment was a combination of Tachigaren applied in the nursery about two days before the plants were transplanted into the field with an application of Ridomil in the field about 5 days after transplanting. Fields that have been disinfected are generally free of summer pythium disease and the young plants generally arrive from the nursery free of the pathogen. Therefore, it appears that in the future, when legal permission is given for the practice, an application of Tachigaren to the young plants before they are transplanted may be sufficient. In plots in which signs of plant collapse following infection with Pythium are observed, one or more applications of Ridomil may be made depending on the level of infection.

  שפה English
  מלות מפתח Capsicum, metalaxyl, hymexazol
  מחבר Shimon Pivonia, Rachel Levite
  שנה 2011
  שייכות yzvieli
  תאריך יצירה 14/3/2012
  תאריך עדכון 14/3/2012
• 8

  Apr
  The effects of soil disinfection and the insertion of crop residue into the soil on pepper yields – A long-term analysis

  Plant Protection, Vegetables

  by Shimon Pivonia, Ph.D.

  הגה"צ; ירקות

  תאריך עדכון 14/3/2012

  תיאור מלא The effects of soil disinfection and the insertion of crop residue into the soil on pepper yields - A long-term analysis
  Shimon Pivonia, Rachel Levite, Ami Maduel – Central and Northern Arava R&D
  E-mail address for correspondence: shimonp@arava.co.il

  Abstract
  Pepper is the main crop in the central Arava and 17,500 dunams (1,750 Ha) in this region were planted to pepper during the 2010/11 growing season. Previously, it was customary to disinfect the soil with methyl bromide before the start of the season. With the end of the use of methyl bromide about five years ago, growers began using metham sodium preparations to disinfect their soil. Since then, in most areas, no particular problems involving soilborne diseases have been observed, aside from a certain increase in the number of plants collapsing as a result of Pythium infection in the winter and the appearance of the new phenomenon of damage to plants caused by the free nematode Pratylenchus penetrans.
  We are conducting a long-term evaluation of the effects of soil-disinfection treatments on pepper development and yield. This study is being conducted on the same ground each year (fixed plots). The study has been conducted for four growing seasons (2007/8, 2008/9, 2009/10 and 2010/11) and we plan to continue this work for two more seasons. During the last two years, we also evaluated the effects of inserting crop residue into the soil (in the same fixed plots). Today, there is a need for alternative solutions for removing and destroying crop residue at the end of the season. The alternative of burying the residue in the field is favored for the significant labor savings it provides as well as for other reasons, as long as it does not negatively affect the next season’s crop.
  This study was set up at the Zohar Experimental Station in Sodom Valley in a greenhouse in which pepper had been grown in the past. We do not know of any particular problems with soilborne pests in this spot before the start of our experiment. The first three years of the study, the pepper cv. Celica was used and, in the year upon which we are currently reporting (2010/11), line 7158 was used. At the end of the first two seasons of the study, we did not see any notable difference between the pepper yield of the control treatment and the yields of the soil disinfection treatments, which included solarization, solarization + Edigan (metham sodium), and Edigan applied through the drip-irrigation system in the absence of any solarization. Despite the fact that no notable yield loss was observed in the untreated control plot, the plants in the untreated control plot did not look as nice. At the end of the third year, the yield of the untreated control was noticeably less than the yields of the other three treatments. In the fourth year, the area that had been used for the untreated control treatment during the previous three years was subjected to a solarization treatment. At the end of the season, we did not notice any yield loss for this treatment. At the end of the second year of the evaluation of the effect of burying crop residue, we did not note any difference between the treatments in which residue from the previous crop was inserted into the soil, green or after having been burnt down with Edigan, and the treatments in which the crop residue was removed from the field.

  Acknowledgement
  We thank the Plant Board for their financial support of this research.

  שפה English
  מלות מפתח Capsicum, soilborne diseases
  מחבר Shimon Pivonia, Rachel Levite, Ami Maduel
  שנה 2011
  שייכות yzvieli
  תאריך יצירה 14/3/2012
  תאריך עדכון 14/3/2012

  OPEN