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Insecticides on the base of Bacillus thuringiensis and B. sphaericus proved to be ineffective against laying of eggs by female mosquitoes in the water containing these formulations.
Various control strategies were evaluated using a previously-described and validated (Focks et al. 1988a, 1988b) simulation model (PcSim) of the population dynamics of Psorophora columbiae breeding in the rice agroecosystem. As expected from field experience, focally-applied ground or aerial ULV aerosols of insecticides were seen to provide local control of peak populations. Similar control was predicted for larvicides when also used in and around urban and suburban areas. Both of these measures were predicted by simulation to provide only short term control of adults as a result of immigration of adults from surrounding, untreated provide only short term control of adults as a result of immigration of adults from surrounding, untreated areas. Evaluations of the effectiveness of diapause egg control or the elimination of early spring broods to provide lasting, season-long suppression were not encouraging if only conventional methods such as insecticides or tillage were used. This was primarily because the ability of Ps. columbiae to recolonize treated areas during the course of a breeding season would require the treatment of prohibitively large, parish- (i.e., county-) sized areas. Evaluations of host management (either removal or residual insecticide treatment of cattle) in and around urban and suburban areas were more encouraging. This technique, by providing continuing pressure on populations, has the potential to offset the impact of immigration and thereby afford long-term suppression in local areas. Finally, evaluations of the impact of modifications to irrigation practices indicated that this approach warrants consideration as a supplemental control technique. These results suggest that field evaluations of model predictions would be useful. They emphasize the need to better understand the movement and spatial distribution of Ps. columbiae. These factors would bear directly on the cost and therefore, the practicality of several of the long-term suppression strategies evaluated as they determine the size of the treatment area surrounding population centers needed to offset the impact of immigration from surrounding, untreated areas.
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The efficacy of Arosurf MSF alone and in combination with three preparations of Bacillus thuringiensis var. israelensis (B.t.i.) against Anopheles albimanus larvae, pupae and eggs was determined by bioassay. Arosurf MSF alone was effective against the egg, 4th larval instar and pupal stages. All Arosurf MSF and B.t.i. combined formulations produced over 90% mortality of all larvae and pupae, 48 hr posttreatment. Egg eclosion was reduced to approximately 25% with all formulations containing Arosurf MSF.
Females and eggs of Toxorhynchites r. rutilus were labeled with 32P by feeding fourth-stage larvae 32P labeled Aedes aegypti larvae. Eggs from females up to 3 weeks in age had detectable levels of radioactivity and individual eggs contained ca. 0.3% of the mother's total radioactivity. Comparisons of labeled and unlabeled females in indoor and outdoor cage tests indicated that survival and fecundity of the 2 groups were approximately equal. No differences were noted for dispersal and fecundity of labeled and control females released in field tests. The 32P-labeled Tx. r. rutilus females behave similarly to unlabeled females, and this method of radiolabeling provides a sound tool for tracking laboratory-reared females released into an area with an indigenous population.
An aerially applied flowable concentrate (FC) of Bacillus sphaericus Neide (isolate 2362) was evaluated against riceland mosquitoes using the Beecomist spray head. Application of the FC at 0.58 and 1.17 liter/ha in maturing rice fields resulted in a 48 hr mean posttreatment reduction of Anopheles quadrimaculatus of 71 and 82%, respectively. A significant reduction in larval populations one week posttreatment was also observed. Treatment rates of 0.29, 0.44, and 0.58 liter/ha in reflooded second crop rice fields resulted in 48 hr posttreatment reduction of Psorophora columbiae larvae of 50, 76 and 98% respectively.
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Campaings to control the German cockroach, Blattela germanica, were conducted at 14-day intervals over a period of 5.5 months on two merchant vessels of similar size and type. On one ship only the chemical "Gertoks", carbamate insecticide containing 1% propoxur was applied, and on the second ship two preparations simultaneously, a chemical and a biological--"Biotrol 25 W" containing Bacillus thuringiensis. - In order to assess the success of the control, the extent of infestation in the accomodation was determined immediately before and 24 h after the spraying. - The susceptibility of the cockroaches caught on the ships, to the two preparations applied, was also determined. It was found that "Gertoks" was an efficient preparation, the biopreparation "Biotrol 25 W" being less efficient. - A certain increase in resistance of the cockroaches to both preparations, was noted. - The above observations indicate that a considerable drop in numbers of population of cockroaches can be achieved if the ship's crew carry out systematic thorough spraying of ships quarters infested by cockroaches, with Gertoks". They also confirm previous suggestions that complex method in B. germanica control on board ships is possible, using chemical and biological preparations containing Bac. thuringiensis spores simultaneously.
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