## 4 Limitations of Using Plant Products as Bioherbicides
### Effect of Nepetalactone and Phloretin on Non-Target Organisms  
#### 4.3.1 Effects on Pollinators and Non-Pollinating Insects  
Detailed studies on how specialized metabolites, such as repetalactone and phloretin, affect non-target organisms when used as bioherbicides are essential. It is well-known that many _Nepeta_ species exhibit repellent activity [81; 285; 286], and it is crucial to carefully assess the potential effects of prospective bioherbicides on beneficial pollinators. While data on the effects of NL on non-target organisms are limited, studies on EOs from other species in the _Lamiaceae_ family provide valuable insights. The toxicity of EOs from mint, oregano, and thyme was tested on two pollinators, _Apis mellifera_ and _Trigona hyalinata_. These EOs did not act as repellents, but they reduced the time pollinators spent in treated areas with sublethal doses. Oregano and thyme EOs decreased the survival of _A. mellifera_, while mint EO was less toxic and more selective. Despite the potential of EOs in weed control, their use must be carefully assessed due to possible negative impacts on pollinators [287]. Despite evidence that phloretin and its derivatives are present in significant quantities in apple floral pollen [288] and in _Camellia oleifera_ bee honey [289], data on the effects of phloretin on insect pollinators remain limited. Honeybees (_Apis mellifera_), mason bees (_Osmia_ spp. ), bumblebees (_Bombus_ spp. ), and hyperflies are considered the primary pollinators of apple flowers, transferring pollen grains from the anthers to the stigmas [290]. Although there are no studies on the effects of phloretin on these pollinators, research by [PERSON] et al. [291] showing that honeybees prefer foraging on apple floral pollen suggests that the phloretin and its glucosides present in the pollen are not harmful to them. However, further studies on a broader range of phloretin concentrations are necessary to assess the dose-dependent effects on pollinators. Considering the impact of phloretin on non-pollinating insects, studies report conflicting findings regarding phloretin and its derivatives, identifying them as either repellents or attractants for various insect pests of apple trees. For example, phlorezin present in apple leaves repels aphids such as _Myzus persicae_ and _Amplorophora agathonica_[292], yet it attracts _Rhopalsiphum insertion_ and the green apple aphid (_Aphis pomi_) [293]. Interestingly, larvae of _Spodoptera litteralis_ have been observed to avoid feeding on previously damaged apple leaves, a behavior associated with increased levels of phlorezin detected in the leaves several days after injury [294]. Furthermore, the percentage of defoliation and the extent of damage on apple leaves caused by adult Japanese beetles (_Popilla japonica_) were found to be inversely proportional to the phlorezin concentrations in the leaves of 10 _Malus_ species. Additionally, the inclusion of phlorezin and phloretin in artificial diets significantly reduced the feeding intensity of Japanese beetles [295]. [PERSON] et al. [296] demonstrated that natural compounds prevalent in the rose family (Rosaceae) exhibited dose-dependent effects on the feeding behavior of adult Japanese beetles, with phloretin inhibiting feeding at concentrations between 1 mM and 10 mM. Finally, the populations of soil mites and Collembolans were significantly reduced in soils affected by ARD [297]. Plant \(\beta\)-glucosidase such as phloretin can negatively impact herbivorous insects by inhibiting insect trehalose activity. Trehalose is the primary circulating sugar in insects, serving as both an energy reserve for flight and a cryoprotectant. Trehalose concentration in the hemolymph is crucial for regulating carbohydrate intake and maintaining nutritional homeostasis [298]. Given its significance, any disruption in trehalose activity can adversely affect insect metabolism, leading to significant developmental and locomotor problems or death [299; 3001].