What young crops are not suitable for mixed planting?

Poplar mixed with larch: the host of poplar stripe rust (or yellow powder disease) such as Populus simonii, Populus cathayensis, Populus pekinensis, Populus euphratica and Populus davidiana. It is Larix gmelinii, which was the earliest disease in that year, and then infected pine leaves, causing early deciduous leaves, dead branches, late leaves and lobules in the following year, which seriously hindered the growth of volume. 2) Mixed planting of Populus tomentosa and Moraceae species: Populus tomentosa was mixed with mulberry, Broussonetia papyrifera, Zheshu and other Moraceae species, and Populus tomentosa was seriously damaged by Apriona germari. This is because the adults of Apriona germari need to eat the tender skin of Moraceae trees to supplement nutrition before laying eggs and hatching into larvae, thus endangering Populus tomentosa; Without Moraceae tree species, Apriona germari can't lay eggs, so it can't complete its life history. 3) Mixed planting of spruce and larch: Larch coccidiosis is easy to occur. Aphids first proliferate on spruce, which not only causes serious harm to larch, but also makes larch tissues stimulated by aphids susceptible to infection with cancer spores. 4) Mixed planting of Picea crassifolia and Prunus mume: Picea crassifolia cones are prone to rust, and infected cones wither and crack early, which reduces the yield and quality of seeds and seriously affects the natural regeneration and seed collection of Picea crassifolia. 5) Mixed planting of Pinus tabulaeformis and Pinus tabulaeformis: The mixed planting of these two tree species is prone to pine needle rust, which is seriously infected, and the windward side is heavier than the leeward side. 6) Mixed planting of apples and pears: When apples and pears are mixed, * * * suffers from fruit rust disease, but pear trees only carry viruses and do not show symptoms. However, after apple infection, the yield and quality decreased, making it inedible and even destroying trees.