Dirk Röse

Sub­stra­te con­cept to com­bat scia­rid infestation

Inter­view with Eck­hard Schlü­ter about major pro­gress in the orga­nic sub­stra­te sector

Eck­hard Schlü­ter works at the Klasmann-Deilmann Advi­so­ry Ser­vices & Qua­li­ty Manage­ment depart­ment and is con­cer­ned pri­ma­ri­ly with the orga­nic sub­stra­te seg­ment. In the fol­lowing inter­view he descri­bes a sub­stra­te and fer­ti­li­ser con­cept for orga­nic substrates that has been deve­lo­ped in col­la­bo­ra­ti­on with Osna­brück Uni­ver­si­ty of App­lied Sci­en­ces and which can redu­ce pres­su­re from scia­rid flies by up to 80 per cent.

Ques­ti­on: Eck­hard, whe­re do scia­rids occur and what are the consequences?

Eck­hard Schlü­ter: Scia­rids are very com­mon and green­houses pro­vi­de ide­al living con­di­ti­ons for a few of the 1800 spe­ci­es that the­re are altog­e­ther. They infest the gro­wing media of orna­men­tals and crops or live on the algae or moss coverings that form in moist are­as. The lar­vae can dama­ge the plant roots. Alt­hough the scia­rids are harm­less for the plants them­sel­ves, they are regar­ded as con­ta­mi­na­ti­on in the tra­de so that retailers may refu­se to accept such plants. Scia­rids are one of the cen­tral plant pro­tec­tion pro­blems in the pro­duc­tion of orga­nic herbs and hor­ti­cul­tu­ral busi­nes­ses are faced with high cos­ts for the bio­lo­gi­cal con­trol of sciarids.

Ques­ti­on: How come the infe­sta­ti­on rates are espe­cial­ly high in the orga­nic sector?

Eck­hard Schlü­ter: We have just dis­co­ve­r­ed that this is due in par­ti­cu­lar to the spe­cial reci­pes used for orga­nic substrates. They cur­r­ent­ly con­tain a mini­mum of 30 per cent of alter­na­ti­ve raw mate­ri­als, such as com­post, wood fib­re or coir, as well as solid orga­nic fer­ti­li­sers. This is in respon­se to demand from orga­nic asso­cia­ti­ons to replace peat to as gre­at an extent as pos­si­ble. Howe­ver, this mix­tu­re unfor­tu­n­a­te­ly offers ide­al living con­di­ti­ons for scia­rid lar­vae. The­re are several rea­sons for this: first­ly, the­se sub­stra­te blends obvious­ly emit sub­s­tan­ces that attract scia­rids and second­ly, they pro­vi­de an excel­lent and direct source of food for the larvae.

Ques­ti­on: What are the­se sub­s­tan­ces that pro­vi­de food for the sciarids?

Eck­hard Schlü­ter: We con­duc­ted lab tri­als to exami­ne all the­se com­pon­ents sys­te­ma­ti­cal­ly. Our tests reve­a­led that sub­stra­te com­pon­ents obtai­ned from com­pos­ting pro­ces­ses pose a par­ti­cu­lar chal­len­ge if they are not pro­per­ly decom­po­sed and still con­tain a high share of easi­ly degrad­able orga­nic mat­ter. It was also clear that the orga­nic fer­ti­li­sers used in the­se pro­ducts obvious­ly play an even more important role. Depen­ding on their com­po­si­ti­on and struc­tu­re, they pro­vi­de a direct source of food for the lar­vae. Howe­ver, the tests also show­ed that our GreenFibre wood fibres and the coir pro­ducts we use are not rea­di­ly acces­si­ble sources of food.

Ques­ti­on: What con­clu­si­ons have you drawn from the tests?

Eck­hard Schlü­ter: As a con­se­quence of the test fin­dings, we are chan­ging the sub­stra­te con­sti­tu­ents we use to depri­ve the lar­vae of their natu­ral food source. What this actual­ly means in prac­ti­ce is that we now use only per­fect­ly rot­ted, matu­re green com­post from our own com­pos­ting plant. This green com­post is mar­ke­ted under the TerrAktiv brand and is high­ly appre­cia­ted in the orga­nic hor­ti­cul­tu­ral busi­ness. As far as the orga­nic fer­ti­li­sers are con­cer­ned, our tests reve­a­led that vir­tual­ly all com­mer­cial­ly avail­ab­le solid fer­ti­li­sers are unsuitable.

We have the­re­fo­re deve­lo­ped an inno­va­ti­ve gel-based fer­ti­li­ser for­mu­la­ti­on in coope­ra­ti­on with a well-known Dut­ch fer­ti­li­ser pro­du­cer. The fer­ti­li­ser is finely dis­tri­bu­t­ed throughout the gro­wing medi­um and its spe­cial encap­su­la­ti­on makes it dif­fi­cult for the scia­rid lar­vae to access. In the cour­se of the deve­lo­p­ment pro­cess, our tech­ni­cal depart­ment also desi­gned a spe­cial dosing sys­tem for the sub­stra­te mixing plant which enab­les micro-fine dis­tri­bu­ti­on of the fertiliser.

Ques­ti­on: What is so spe­cial about this concept?

Eck­hard Schlü­ter: The­re are actual­ly two spe­cial fea­tures: first­ly, the idea that dif­fe­rent modu­les can be com­bi­ned in any given sub­stra­te to match the indi­vi­du­al needs of the com­pa­ny con­cer­ned. The­se modu­les are white peat, coco, wood fib­re and – a very important aspect – we can still con­ti­nue to work with a share of valu­able green com­post in orga­nic substrates. TerrAktiv green com­post invi­go­ra­tes the sub­stra­te, sup­pres­ses patho­gens and pro­mo­tes the mine­ra­li­sa­ti­on of orga­nic fertilisers.

The second thing is our new fer­ti­li­ser for­mu­la­ti­on, which con­sists of fer­men­ted vege­ta­ble or hydro­ly­sed ani­mal com­pon­ents. The­se fer­ti­li­sers are high­ly effi­ci­ent in pro­vi­ding nut­ri­ents and are also rich in ami­no acids, which help to streng­t­hen the plants. They can­not be used direct­ly by scia­rid lar­vae and the­re­fo­re enab­le hor­ti­cul­tu­ral busi­nes­ses to use orga­nic substrates with a signi­fi­cant­ly hig­her level of basic fer­ti­li­sa­ti­on again.

Ques­ti­on: And this sub­stra­te con­cept stands for genui­ne progress?

Eck­hard Schlü­ter: Yes, we have been using this con­cept with an incre­a­sing num­ber of cus­to­mers for some years and the results are very posi­ti­ve. Thanks to the expe­ri­ence we have acqui­red to date, we are now in a posi­ti­on to offer a cus­to­mi­sed fer­ti­li­sa­ti­on con­cept for each grower.

In respon­se to incre­a­sing demand from Bene­lux and Fran­ce, we are cur­r­ent­ly also instal­ling a fer­ti­li­ser dosing sys­tem for orga­nic substrates at our pro­duc­tion plant in the Netherlands.

Ques­ti­on: Who will bene­fit from this sub­stra­te concept?

Eck­hard Schlü­ter: It is pri­ma­ri­ly sui­ta­ble for hor­ti­cul­tu­ral com­pa­nies loo­king for orga­nic herb gro­wing media with a low to medi­um level of basic fer­ti­li­sa­ti­on which they can com­bi­ne with their own later liquid fer­ti­li­sa­ti­on stra­te­gy. This com­bi­na­ti­on is cur­r­ent­ly the most effi­ci­ent way to con­trol pres­su­re from sciarids.

Howe­ver, it has also shown other pro­mi­sing poten­ti­al uses in gro­wing media for sen­si­ti­ve young vege­ta­ble plants. The fer­ti­li­ser is released at a care­ful rate and we also noti­ced that the free ami­no acids yiel­ded stron­ger plants.

Eck­hard, thank you for taking the time to talk to us.