is 50–90 per square meter and loblolly and slash pine at less than 215 seedlings per square meter. Biological The act of releasing native or nonnative predators of pest species is uncommon in forest integrated pest management. It would not be economically feasible to utilize this method in a forestry scenario. Instead, the forest and its surrounding area is managed in a way to promote natural enemies of pest species. In a study of eucalyptus plantations in Brazil, the closer the plantation is to a "natural" more diverse forest, the more diverse and balanced the insect populations are. This more diverse environment is less likely for produce an outbreak of pest species. Bacillus thuringiensis (Bt) is a bacterium that is used to kill larvae of many pest species. This can be applied aerially or on the ground over large surfaces. Bt is safe for humans and other wildlife since it only infects certain species of insects. Chemical Integrated pest management was designed after Rachael Carson's Silent Spring as a way to manage for pests without overusing pesticides. Chemicals are still used but in a way that focuses on proper use of pesticide application so overuse does not occur. The fungicide triadimefon is applied to loblolly and slash pine seeds to prevent fusiform rust. If the seeds used are not treated for fusiform rust, the stand can lose 1–30% of their trees to the rust. Longleaf pine is naturally resistant to fusiform rust so their seeds are not treated with triadimefon. Southern pine nurseries fumigate the soil every four years and hardwood nurseries fumigate yearly. Fumigation promotes growth of beneficial fungus Trichoderma and less of the harmful Phythium fungus. In forest integrated pest management, insecticides are not applied until an infestation is observed. Herbicides are used to control weeds in nurseries. Low rates and frequent application intervals of herbicide is what is recommended. Eucalyptus plantations Eucalyptus plantations provide a unique management challenge since they are commonly grown out of their native range and also in monocultures of clones. Large homogeneous areas of one species of tree are more susceptible of pest attacks. This is due to an abundant and predictable amount of food for the pest, and an absence of their natural enemies. There are less predator species in monocultures because the plants they need to forage, rest and lay eggs on are not there. This combination is why monoculture environments