Maggot Growth Research Articles

Could blackbird mortality from avicide DRC-1339 contribute to avian botulism outbreaks in North Dakota?

Blackbird (family Icteridae) depredation on sunflower (Helianthus annuus) crops in the prairie states of the United States has motivated the proposed use of an avicide, DRC-1339 (3-chloro-4-methylaniline), to decrease their numbers. The resulting mortality of black- birds at wetland roosts could increase the potential of avian botulism occurring in affect- ed marshes. To assess this possibility, we seeded (artificially placed) blackbird carcasses in selected wetlands in Stutsman County, North Dakota, during August-September 2000 and July-September 2001 to evaluate their rate of decomposition and role in initiating avian botulism outbreaks. We monitored carcasses to determine their persistence, the frequen- cy and amount of maggots produced, and the presence of type C botulinum toxin. In 10 of our 12 study wetlands, blackbird carcasses were not rapidly removed by scavengers, thus providing substrate for maggot growth and potential production of Clostridium botu- linum toxin. Decomposition of carcasses occurred rapidly, and maggot production aver- aged 4-5 g per carcass within 9 days. We were unable to detect C. botulinum type C toxin in any of the 377 blackbird carcasses or the 112 samples of maggots we collected in 2000 or 2001. None of the 25 blackbird carcasses we tested contained botulinum spores, the most probable explanation for the absence of botulinum toxin production. Our results indicate that the likelihood of DRC-1339-poisoned blackbirds causing botulism outbreaks would be minimal in North Dakota wetlands during late summer and early autumn.

Relationship between selected bacteria and the growth of immature house flies, Musca domestica, in an axenic test system.

To investigate the relationship between immature (maggot) house flies, Musca domestica, and bacteria, we compared the development of sterile first-instar maggots in each of 10 pure blood agar cultures of bacteria with growth on sterile blood agar (negative control) and on standard house fly rearing medium (positive control). Nine species of bacteria representing gram-negative and gram-positive rods, coccoid, and micrococcoid cell types supported house fly growth on blood agar. One bacterium, a strain of Bacillus cereus, inhibited maggot growth. The percent pupation for maggots that developed in the presence of eight of nine bacteria (range, 41-69%), was significantly greater than in sterile blood agar (0-5%), and did not differ significantly from maggot growth in the rearing medium (50-90%). Average pupal weight for maggots that developed on blood agar with bacteria ranged from 19 to 21 mg, a reflection of favorable growth conditions. Average pupal weight in the presence of three bacteria (19.9, 19.4, and 19.4 mg) was significantly less than respective pupal weights in house fly rearing medium (24.0, 22.3, and 22.1 mg), but there was no difference in average pupal weight with six bacteria and the house fly rearing medium. These findings illustrate that bacteria or their metabolic products are essential as nutrients for house fly maggot growth in blood agar; a wide variety of adventitious bacteria can contribute to the suitability of an organic substrate for maggot growth; and a naturally occurring isolate of B. cereus limits house fly maggot growth in blood agar, a relationship that has not been reported previously.

Effect of experimental bedding treatments on the density of immature Musca domestica and Stomoxys calcitrans (Diptera: Muscidae) in outdoor calf hutches.

Experimental bedding materials and a novel delivery method of cyromazine (Larvadex) were evaluated as replicated treatments in outdoor calf hutches for effect on the density of immature Musca domestica L. and Stomoxys calcitrans (L.). In 6-wk trials, overall density of Musca domestica L. and Stomoxys calcitrans (L.) in straw bedding averaged 36.2 and 52.6 maggots/liter, respectively, compared with respective average densities of 9.0 and 16.2 for wood chips and 10.4 and 20.0 for wood chips over a hydraulic fabric filter system. These values represent average reductions of 80 and 69% and 77 and 68%, respectively. Densities of M. domestica and S. calcitrans in ground corncob over the filter system averaged 13.3 and 4.1 maggots/liter in 3.2-mm size corncob particles, and 1.7 and 1.2 for 6.4-mm size corncob particles (average reductions of 62 and 87% and 90 and 96%, respectively) relative to straw bedding. Densities of these two species in sand bedding averaged 2.8 and 0.4 maggots/liter (average reductions of 93 and 99%), but sand became compacted and soiled with calf urine and feces after several weeks. Cyromazine excreted in calf urine limited density of both species in straw to an average of 11.0 and 15.6 maggots/liter, respectively (a 58 and 79% suppression relative to untreated straw). These data confirm that straw bedding promotes muscoid maggot growth and illustrate that alternative calf hutch bedding systems and urine delivery of cyromazine may improve muscoid fly management on dairy farms by limiting the development of muscoid maggots.