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For now , however , sanitation ( promptly removing and destroying fallen fruit and leaves ) , cultural practices designed to promote optimum tree health , and perhaps occasional physical or chemical intervention are all that is normally needed to obtain a satisfying crop in most years . 2.3 and 2.4 ) have both been identified in SAR interferometry images ( Massonnet and Feigl , 1995a ) . At that point , caterpillars have grown to about 1 to 2 inches in length . Susceptibility varies among daylily cultivars , but none are known to be resistant . Although pear trees are generally susceptible to a number of disease and insect problems , the fact that they are relatively uncommon in the Minnesota landscape often prevents these problems from becoming severe for home gardeners . Leave more fruit on the outer portion of the tree and less in the shaded center , where it will not get good sunlight . Dig the holes large enough to accommodate all the roots and deep enough so you can cover the uppermost roots with 3 to 4 inches of soil . Secure the netting so there is no place for the birds to enter . If you discover iris borer damage early in the season , you can crush the insect while it is inside the leaf or remove the infested leaf . If growth is normal , however , apply a low-phosphorous fertilizer , such as a lawn fertilizer containing no herbicide , at the rate of 1 ounce of actual nitrogen per year of tree age , not to exceed 16 ounces . It begins early in the spring when the shoots are about six inches tall . Most garden soils in Minnesota have pH readings above those that are optimum for blueberries ( most soils are too alkaline ) . By this we mean that , within a given pixel , the position of radar scatterers has not changed to any significant degree , but the ensemble of scatterers ( i.e ., the entire ground surface within that pixel , as well as some adjacent ones ) has moved up , down , or sideways in some correlated fashion . Pruning the trunk back in this way is intended to induce branching that will result in scaffold branch options the following year . Both temperature and humidity are important factors in the development of powdery mildew . No fungicides are currently labeled for control of foliar diseases on daylilies . Both species ( Heterorhabditis and Steinernema ) have been shown to attack iris borer . They are both scarab beetles belonging to the same subfamily , shining leaf chafers ( Rutelinae ) . In principle , all three compo-nents of surface displacement could be obtained from space ; in practice , we are only likely to obtain at most two , if data from both the ascending and descending passes of the satellite are available . A preventive spray program can include the chemicals listed in table 1 . There is no cure for plants severely damaged by soft rot . North-facing slopes and sites that experience winter shade would both work well . There are currently no fungicides available to homeowners for white mold control .