Abstract
The topical toxicities of five commercial grade pesticides commonly sprayed in apple orchards were estimated on adult worker honey bees, Apis mellifera (L.) (Hymenoptera: Apidae) and Japanese orchard bees, Osmia cornifrons (Radoszkowski) (Hymenoptera: Megachilidae). The pesticides were acetamiprid (Assail 30SG), λ-cyhalothrin (Warrior II), dimethoate (Dimethoate 4EC), phosmet (Imidan 70W), and imidacloprid (Provado 1.6F). At least 5 doses of each chemical, diluted in distilled water, were applied to freshly-eclosed adult bees. Mortality was assessed after 48 hr. Dose-mortality regressions were analyzed by probit analysis to test the hypotheses of parallelism and equality by likelihood ratio tests. For A. mellifera, the decreasing order of toxicity at LD50 was imidacloprid, λ-cyhalothrin, dimethoate, phosmet, and acetamiprid. For O. cornifrons, the decreasing order of toxicity at LD50 was dimethoate, λ-cyhalothrin, imidacloprid, acetamiprid, and phosmet. Interaction of imidacloprid or acetamiprid with the fungicide fenbuconazole (Indar 2F) was also tested in a 1∶1 proportion for each species. Estimates of response parameters for each mixture component applied to each species were compared with dose-response data for each mixture in statistical tests of the hypothesis of independent joint action. For each mixture, the interaction of fenbuconazole (a material non-toxic to both species) was significant and positive along the entire line for the pesticide. Our results clearly show that responses of A. mellifera cannot be extrapolated to responses of O.cornifrons, and that synergism of neonicotinoid insecticides and fungicides occurs using formulated product in mixtures as they are commonly applied in apple orchards.
Highlights
Pollinator species such as honey bee [Apis mellifera (L.) (Hymenoptera: Apidae)] and the Japanese orchard bee [Osmia cornifrons (Radoszkowski) (Hymenoptera: Megachilidae)] provide important services in orchard and other agricultural ecosystems [1]–[6]
The least toxic group consisted of phosmet, acetamiprid and imidacloprid. l-cyhalothrin was significantly more toxic than the first group, and the most toxic pesticide, dimethoate, was,70 times more toxic than phosmet
Our results clearly show that the response of A. mellifera cannot be extrapolated to the response of O.cornifrons
Summary
Pollinator species such as honey bee [Apis mellifera (L.) (Hymenoptera: Apidae)] and the Japanese orchard bee [Osmia cornifrons (Radoszkowski) (Hymenoptera: Megachilidae)] provide important services in orchard and other agricultural ecosystems [1]–[6]. The Japanese orchard bee ( known as the Japanese horn-faced bee) is commercially used for pollination of pears and apples in Japan [9] This species was introduced into the mid-Atlantic region of the United States by USDA scientists in 1977 [10], [11], has since become commercially available, and is an important (and efficient) wild pollinator in tree fruit orchards in Pennsylvania [12], [13]. One O. cornifrons can set up to 80% more apple flowers per day compared with flowers set by one honey bee, A. mellifera (L.), worker [14] These two species are complementary pollinators of apple, peach and pear orchards in the Northeastern United States [12], [13], [15]–[19]
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