Sampling and distribution of Anopheles quadrimaculatus immatures in rice fields.

Dipper samples of Anopheles quadrimaculatus immatures from stocked enclosures in Arkansas rice fields were used to develop regression equations relating dipper sample counts to absolute density. Confidence limits were developed for mean number of immatures collected at each density and stadia, including combined stadia. These data can be used to estimate absolute density from mean dipper count. Distribution of rice field immatures approximated but did not fit the Poisson distribution. Sample size was calculated for 10, 25 and 50% of the true mean, at various levels of Type I and II error. A sample size of N = 6,424 was necessary to detect differences within 10% of the true mean, with 5 and 10% probability of Type I and II error, respectively.

Combination ground and aerial adulticide applications against mosquitoes in an Arkansas riceland community.

Simultaneous ground and aerial adulticide applications were evaluated against riceland mosquitoes in Stuttgart, AR, during July 1985. Naled was aerially applied at 52.6 ml/ha over 10.4 km2 surrounding the city. Ground ULV applications of a mixture of malathion, HAN and resmethrin/PBO (1:1:0.0625) were applied within the city at a rate of 221.8 ml/min at 24 kph. Adult populations of Anopheles quadrimaculatus and Psorophora columbiae were reduced at 24 hr but resurgence of Ps. columbiae was evident at 48 hr posttreatment. Posttreatment data indicated that movement of both mosquitoes occurred along the path of prevailing wind.

Swath width determination for Beecomist-applied Bacillus thuringiensis (H-14) against Anopheles quadrimaculatus larvae in rice fields.

Optimum flight path interval of Beecomist-applied Bacillus thuringiensis var. israelensis (serotype H-14) (Bti) against Anopheles quadrimaculatus larvae was determined by assessing the effective swath width in rice fields. Droplet sensitive cards, laboratory-reared and naturally occurring populations of larvae were used to monitor aerial treatments 1 day posttreatment. Overlapping swaths were necessary to provide high levels of larval reduction. Based on tests where flight path intervals were 18.3, 36.6 and 73.2 m, optimal flight path interval was estimated to be approximately 67 m downwind of the extreme downwind flight path when flow rate was 1.44 liter/min.

Evaluation of Beecomist-applied Bacillus thuringiensis (H-14) against Anopheles quadrimaculatus larvae in rice fields.

The Beecomist spray head was evaluated for aerial application of Bacillus thuringiensis var. israelensis (serotype H-14; Bti) at various ultra low volume (ULV) rates against natural populations of Anopheles quadrimaculatus larvae in rice fields. Deposits on Kromekote cards indicated that 0.54 liter/ha of neat Bti penetrated the dense canopy of the rice field. Mean number of droplets 65 cm below canopy level was 4.9 +/- 5.0/100 cm2. At 1 day posttreatment, applications of 0.54, 0.27, 0.11, 0.07 and 0.04 liter of Bti/ha resulted in reductions of 97.9, 94.4, 93.0, 71.1 and 21.8%, respectively, of An. quadrimaculatus larvae/dip. Calculated lethal field dosages (LFD50 and LFD90) were 0.05 and 0.16 liter/ha, respectively.