regulates modulation of formation of structure involved in a symbiotic process regulation of developmental process modulation by symbiont of entry into host biological regulation haustorium neck formation modulation of symbiont haustorium neck formation for entry into host Note that this term should not be used to annotate gene products of the host. It should only be used to annotate those gene products from the symbiont involved in this process. Any process that modulates the frequency, rate or extent of symbiont haustorium neck formation for entry into host. The host is defined as the larger of the organisms involved in a symbiotic interaction. biological_process GO:0075198