NUMERICAL RESPONSES OF NATURAL ENEMIES TO ARTIFICIAL HONEYDEW IN UTAHALFALFA

Artificial honeydews were applied to alfalfa plots in field experiment s during the second (1992) and third (1991 and 1992) crops in northern Utah. Individual plots received a single application of sucrose disso lved in water; protein supplement and water; sucrose, protein suppleme nt, and water; or water alone. Sweep samples were taken for entomophag ous arthropods over a period of 4 d (second crop) or 10 d (third crop) after treatment spray applications. Application of sucrose, but not o f protein supplement, resulted in reduced densities of aphids (relativ e to those in plots sprayed with water only). Adult lacewings and lady beetles consistently responded positively to application of sucrose. Lacewings during the second and third crops in 1992 and lady beetles d uring the third crop in 1991 also responded positively to application of protein supplement, with greatest densities occurring in plots spra yed with both materials. Positive responses to application of sugar by adults of the alfalfa weevil parasitoid, Bathyplectes curculionis (Th omson), and adult hover flies, bigeyed bugs, and minute pirate bugs (b ut not spiders or adult damsel bugs) were also detected in one or more experiments. None of these groups, however responded consistently or clearly to application of protein supplement In the absence of rain, p ositive responses by particular natural enemies to sugar, protein supp lement, or both, persisted for up to 7 d after application. Our experi mental results add to those of previous research indicating that local populations of a variety of entomophagous insects, including parasito ids with non-aphid hosts, can be increased in crops by application of artificial honeydew.