. Control of diabrotica, or Western spotted cucumber beetle, in deciduous fruit orchards. Diabrotica; Diabrotica; Fruit. 22 University of California—Experiment Station orchard area? It hardly seems possible that a brood develops on the grasses growing in the orchards. However, in many orchards there is a rank growth of water grass (Echinochloa Crus-galli) and other weeds that might support a large larval diabrotica population. The origin of the beetles that make up this large midsummer brood certainly needs further investigation. The beetles migrate into deciduous fruit trees because of the fa
. Control of diabrotica, or Western spotted cucumber beetle, in deciduous fruit orchards. Diabrotica; Diabrotica; Fruit. 22 University of California—Experiment Station orchard area? It hardly seems possible that a brood develops on the grasses growing in the orchards. However, in many orchards there is a rank growth of water grass (Echinochloa Crus-galli) and other weeds that might support a large larval diabrotica population. The origin of the beetles that make up this large midsummer brood certainly needs further investigation. The beetles migrate into deciduous fruit trees because of the favorable con- ditions that they offer. The leaves give an ample food supply, and the shade afforded allows the beetles to escape from the heat; they are likely to be found most abundant in the trees that have the densest foliage. Even in these trees there is a movement of the beetles towards the shady side as the temperature rises during the hottest part of the day. On many occasions in making popula-. MAY JUNE JULY AUG. Fig. 14.—Diabrotica population trends for 1941 in the same three orchards as shown in figure 13. The graph identification is the same. Note the drop in population in the two orchards with high diabrotica population, as a result of dusting. tion counts in early morning, it was noted that many more beetles fell to the sheets on the east side than on the west side of the trees. This distribution beyond a doubt resulted from many beetles moving to the east side of the trees to escape the hot afternoon sun. Because denseness of foliage is an important factor, peach and nectarine trees generally offer a more suitable environment for the beetles than do apricot trees. This is particularly true of the younger peach and nectarine trees. In the case of the apricot trees the beetle population has always fallen off rather abruptly as soon as the crop is harvested. While the ripe or nearly ripe fruit is still on the trees the beetles find conditions most favorable for th
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