Root-knot nematodes (Meloidogyne spp.) are a worldwide problem in many crops. These nematodes are a particular problem in glasshouse-grown chrysanthemums. In order to combat root-knot nematodes in the glasshouse, the soil is typically steamed every 5-6 growth cycles. However, this method is expensive, environmentally unfriendly and reduces the resistance and resilience of the soil against other pathogens and pests. In this experiment we added different biological pesticides and basic substances and biostimulants both individually and in combination in order to determine if there is an interactive or additive effect against damage caused by root-knot nematodes in chrysanthemums. We found that the use of the biological pesticide derived from garlic extract and the basic substance chitosan HCl and biostimulants comprised of sea minerals and plant oils reduced the damage to chrysanthemum caused by root-knot nematodes. A number of the treatments caused a reduction in plant biomass (e.g., soldier fly waste products and their interaction with chitosan HCl and interactions between the chemical nematicide oxamyl and several of the biostimulants). However, this reduction was minimal.