In the control of codling moth it is common to combine the granulovirus with other agents,

especially fungicides, in spray application. Therefore the knowledge about the influence of

these agents on the efficacy of the virus in tank mix is very important. Studies on this

subject were part of a project supported by BMELV (German Federal Ministry for Food,

Agriculture and Consumer protection) at the Institute for Biological Control of JKI in

Darmstadt.

The granulovirus of Cydia pomonella (L.) (CpGV) was mixed with 10 different agents at

concentrations as applied in the field. After the exposure the virus activity was calculated

from larval mortality determined in bioassays with neonates of a susceptible codling moth

strain.

Only two agents with a pH of 11 (sodium silicate (water glass) and calcium polysulfide

(lime sulphur)) reduced the virulence of CpGV significantly

Fritsch, E.

Huber, J.

Kienzle, J.

Undorf-Spahn, K.

English

Organic Eprints

252Impact of different Agents on the Efficacy of Codling Moth Granulovirus in Tank Mixtures E. Fritsch1; K. Undorf-Spahn1, J. Huber1, J. Kienzle2AbstractIn the control of codling moth it is common to combine the granulovirus with other agents, especially fungicides, in spray application. Therefore the knowledge about the influence of these agents on the efficacy of the virus in tank mix is very important. Studies on this subject were part of a project supported by BMELV (German Federal Ministry for Food, Agriculture  and  Consumer  protection)  at  the  Institute  for  Biological  Control  of  JKI  in Darmstadt. The granulovirus of Cydia pomonella (L.) (CpGV) was mixed with 10 different agents at concentrations as applied in the field. After the exposure the virus activity was calculated from larval mortality determined in bioassays with neonates of a susceptible codling moth strain.Only two agents with a pH of 11 (sodium silicate (water glass) and calcium polysulfide (lime sulphur)) reduced the virulence of CpGV significantly.Key words: Plant protection, codling moth granulovirus, Cydia pomonella, tank mixture, virus inactivation IntroductionWith  the  increasing  resistance  of  codling  moth  strains  against  CpGV  it  is  even  more important than before that the CpGV applied in the field is not completely or even partly inactivated by tank mixture with other products (Asser-Kaiser et al., 2007). In the first years of CpGV application in organic fruit growing,  the main fungicide was wettable sulphur. Since it was well known, that a tank mixture of wettable sulphur and CpGV was possible, it became common practice to combine fungicidal treatments with CpGV. Due to this, CpGVcould be applied in short intervals without the need of separate applications. Today, there are more fungicides to be considered, as, e.g. lime sulphur and copper which is used in low concentrations also after blossom. With increasing infestation of sooty blotch even other  treatments  as  potassium,  sodium  bicarbonate  and  water  glass  (sodium  silicate) became important. It was not so clear, if there would be no inactivation of CpGV in tank mix with these substances. Furthermore, mainly in the region of Lake Constance, a special kind of whey with rather acid pH was used against spider mites. Calcium chloride is often used against bitter pit during the second generation of codling moth. Also in this case the question  of  miscibility  with  CpGV  arose.  The  aim  of  this  study  was  to  test  if  different products lead to an inactivation of CpGV if applied in tank mix. Commercial products The  following  commercial  products  used  in  organic  apple  production  were  tested  with regard to effects on virus stability. In practice the calculation of the dosage is based on 2 m high trees and a water volume of 300  l  per  hectare.  For  bioassays  the  products  were  prepared  with  the  same  dosages before CpGV was added. 1 Julius Kühn-Institut, Federal Research Centre for Cultivated Plants, Institute for Biological Control, Heinrichstr. 243, D-64287 Darmstadt, Germany, jürg.huber@jki.bund.de2 Apfelblütenweg 28, D-71394 Kernen, Germany, jutta@jutta-kienzle.deArchived at http://orgprints.org/13704/253Impact of different Agents on the Efficacy of Codling Moth Granulovirus in Tank Mixtures E. Fritsch1; K. Undorf-Spahn1, J. Huber1, J. Kienzle2AbstractIn the control of codling moth it is common to combine the granulovirus with other agents, especially fungicides, in spray application. Therefore the knowledge about the influence of these agents on the efficacy of the virus in tank mix is very important. Studies on this subject were part of a project supported by BMELV (German Federal Ministry for Food, Agriculture  and  Consumer  protection)  at  the  Institute  for  Biological  Control  of  JKI  in Darmstadt. The granulovirus of Cydia pomonella (L.) (CpGV) was mixed with 10 different agents at concentrations as applied in the field. After the exposure the virus activity was calculated from larval mortality determined in bioassays with neonates of a susceptible codling moth strain.Only two agents with a pH of 11 (sodium silicate (water glass) and calcium polysulfide (lime sulphur)) reduced the virulence of CpGV significantly.Key words: Plant protection, codling moth granulovirus, Cydia pomonella, tank mixture, virus inactivation IntroductionWith  the  increasing  resistance  of  codling  moth  strains  against  CpGV  it  is  even  more important than before that the CpGV applied in the field is not completely or even partly inactivated by tank mixture with other products (Asser-Kaiser et al., 2007). In the first years of CpGV application in organic fruit growing,  the main fungicide was wettable sulphur. Since it was well known, that a tank mixture of wettable sulphur and CpGV was possible, it became common practice to combine fungicidal treatments with CpGV. Due to this, CpGVcould be applied in short intervals without the need of separate applications. Today, there are more fungicides to be considered, as, e.g. lime sulphur and copper which is used in low concentrations also after blossom. With increasing infestation of sooty blotch even other  treatments  as  potassium,  sodium  bicarbonate  and  water  glass  (sodium  silicate) became important. It was not so clear, if there would be no inactivation of CpGV in tank mix with these substances. Furthermore, mainly in the region of Lake Constance, a special kind of whey with rather acid pH was used against spider mites. Calcium chloride is often used against bitter pit during the second generation of codling moth. Also in this case the question  of  miscibility  with  CpGV  arose.  The  aim  of  this  study  was  to  test  if  different products lead to an inactivation of CpGV if applied in tank mix. Commercial products The  following  commercial  products  used  in  organic  apple  production  were  tested  with regard to effects on virus stability. In practice the calculation of the dosage is based on 2 m high trees and a water volume of 300  l  per  hectare.  For  bioassays  the  products  were  prepared  with  the  same  dosages before CpGV was added. 1 Julius Kühn-Institut, Federal Research Centre for Cultivated Plants, Institute for Biological Control, Heinrichstr. 243, D-64287 Darmstadt, Germany, jürg.huber@jki.bund.de2 Apfelblütenweg 28, D-71394 Kernen, Germany, jutta@jutta-kienzle.deTable 1: Commercial formulations used together with CpGV in tank mix for control of codling moth. Commercial products Dosage in 300 litre per haConcentrationper 100 ml water H-ionconcentrationpHWhey   14 kg  4,67 gr  4 Sodium bicarbonate  5 kg  1,67 gr  8.5 Sodium silicate (water glass)  5 litre  1,67 ml  11 Calcium chloride (Düngal)  20 litre  6,67 ml  7 Potassium bicarbonate (Vitisan)  5 kg  1,67 gr  9 Potassium bicarbonate (Armicarb) 5 kg  1,67 gr  8.5 Copper liquid (Cuprozin)  0,66 litre  0,22 ml  7 Copper WP (Cuprozin WP 24158) 0,44 kg  0,148 gr  7Sulphur (Stulln)   4 kg  1,33 gr  7 Lime sulphur  15 litre  5,0 ml  11.5 Water  -  100 ml  7 Virus The  granulovirus  of  the  codling  moth  used  in  the  bioassays  is  a  descendent  from  the CpGV collected in Northern Mexico (“Mexican strain”) (Tanada, 1964). It was propagated in host insects and purified by the method described by Huber (1981). Test insects Larvae of a laboratory strain of the codling moth, Cydia pomonella, served as test insects in the bioassays. This laboratory strain has been established more than thirty years ago at the Institute for Biological Control of the BBA in Darmstadt. The rearing method has been described by Bathon (1981). Bioassay method For the assays each agent was dissolved in 100 ml of water at the amount given in table 1.CpGV was added to these suspensions (1.5 x 106 G/ml) and held at room temperature for 4  hours  corresponding  to  the  conditions  during  field  application.  Additionally  a  water suspension of CpGV was prepared as a control. The pH was determined by colour-fixed indicator sticks. Samples were removed 4 hr after mixing and assayed for infectivity using the bioassay method described by Huber (1981). Therefore, aliquots of the prepared solutions were incorporated  by  thorough  mixing  into  an  artificial  diet  (Ivaldi-Sender,  1974)  kept  at  a temperature of 45 °C in a water bath. The bioassay diet was dispensed into special boxes (LICEFA, Bad-Sulzuflen, Germany) with 50 separate cells (1.5 x 1.5 x 2 cm) and the next day one neonate larva was placed in each cell.The boxes were covered with a layer of tissue paper, a polyethylen sheet, and a hard-plastic cover, and fixed with two rubber bands. The boxes were incubated at 26°C, 60-70% RH  with  a  16  hr  photoperiod  and  larval  mortalities  were  recorded  after  14  days.  Only copper wettable powder (Cuprozin WP 24158) was tested in a bioassay incubated for 7 days. For each bioassay the solutions were diluted so that the CpGV concentration in the diet was equivalent to a LC90.Archived at http://orgprints.org/13704/254From the mortality data of the bioassays virus activity was calculated by using the dose response regression line of a standard bioassay. Results and discussion In the bioassays the larval mortality was recorded and used for the calculation of the viral activity. These data are presented in figure 1. Obviously only two products, water glass and lime sulphur reduced the viral activity substantially. After exposure in the water glass solution  the  virus  retained  27%  of  its  original  activity.  After  exposure  in  lime  sulphur solution, the activity was only 14 %. In the suspensions of these chemical compounds the viruses were exposed to high H-ion concentrations of pH 11. The other products ranging from pH 4 to pH 9 had no inactivating effect on the viruses and caused larval mortalities similar to that of CpGV suspended in water. The new product Cuprozin wettable powder tested in a 7 day bioassay showed as well as Cuprozin liquid no reduction of virulence (figure 2). Studies  on  the  stability  of  a  nucleopolyhedrosis  virus  of  Heliothis zea  (corn  earworm) showed that its infectivity was reduced when the virus was buffered at pH 2 or 12 but was unaffected at pH 5, 7, or 9 (Gudauskas & Canerday, 1968). The stability of baculoviruses is due to the intact inclusion body embedding the virions. At strong alkaline conditions the inclusion body will be dissolved. Jaques (1977) reported that residues of various chemicals (bicarbonates, sodium, potassium and calcium) found in dew on leaves can have an effect on baculoviruses. Our results show that CpGV should not be combined in tank mix with lime sulphur or water glass in order to avoid an inactivation. Any effect of tank mix with the other commercial products in the tested dosage is not to be expected. 110100waterwheysodium bicarbonatewater glassDüngalVitisanlime sulphurArmicarbCuprozin liquidsulphurFormulation% ActivityFigure  1:  Activity  of  CpGV  after  4  hr  exposure  to  different  formulations,  calculated  from  larval mortality after 14 days in bioassays. Archived at http://orgprints.org/13704/255110100water CuprozinWPlimesulphurFormulation% ActivityFigure  2:  Activity  of  CpGV  after  4  hr  exposure  to  different  formulations,  calculated  from  larval mortality after 7 days in bioassays. References Asser-Kaiser, S., Fritsch, E., Undorf-Spahn, K., Kienzle, J., Eberle, K. E., Gund, N. A., Reineke, A., Zebitz, C. P. W., Heckel, D. G., Huber, J., Jehle, J. A. (2007). Rapid emergence of baculovirus resistance in codling moth due to dominant, sex-linked inheritance. Sience 318: 1916-1918. Bathon, H. (1981). Zur Zucht des Apfelwicklers, Laspeyresia pomonella (L.) (Lep., Tortricidae), auf einem künstlichen Nährmedium. Mitt. dtsch. Ges. allg. angew. Entomol. 2: 136-140. Gudauskas, R. T. & Canerday, D. (1968). The effect of heat, buffer, salt and H-ion concentration, and ultraviolet light on the infectivity of Heliothis and Trichoplusia nuclear polyhedrosis viruses. J. Invertebr. Pathol. 12: 405-411. Huber,  J.  (1981).  Apfelwickler-Granulosevirus:  Produktion  und  Biotests.  Mitt.  dtsch.  Ges.  allg. angew. Entomol. 2: 141-145. Ivaldi-Sender, C. (1974). Techniques simples pour élévage permanent de la tordeuse orientale, Grapholita molesta (Lep., Tortricidae), sur milieu artificiel. Ann. Zool. Ecol. Anim., 6: 337-343. Jaques, R. P. (1977). Stability of entomopathogenic viruses. Misc. Publ. Entomol. Soc. Am. 10: 99-116.Archived at http://orgprints.org/13704/

Impact of different Agents on the Efficacy of Codling Moth Granulovirus in Tank Mixtures

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