Rw. Behle et al., EXTENDING THE RESIDUAL TOXICITY OF BACILLUS-THURINGIENSIS WITH CASEIN-BASED FORMULATIONS, Journal of economic entomology, 89(6), 1996, pp. 1399-1405
We evaluated the extension of the residual insecticidal activity of Ba
cillus thuringiensis Berliner with 2 sprayable formulations based on c
asein. One formulation contained native casein in a basic solution (pH
> 8.5); the other had a water soluble ammonium salt of casein in tile
presence of ammonium zirconium carbonate as a cross-linking agent. Fo
rmulations were applied to cotton leaves, Gossypium hirsutum L. 'DES 1
19', in a greenhouse and subjected to simulated rain in a modified spr
ay chamber and artificial sunlight from a simulator. Activity was asse
ssed based on mortality of neonate European corn borer, Ostrinia nubil
alis (Hubner), that were fed treated cotton leaves. Performance of som
e formulations was also evaluated against beet armyworm, Spodoptera ex
igua (Hubner). Leaves treated with the casein formulations (0.5% wt:vo
l) of B. thuringiensis resisted wash-off, often retaining >60% of the
original insecticidal activity of unexposed treatments compared with <
20% of the original activity for unformulated and commercially formula
ted B. thuringiensis preparations. The casein formulations also provid
ed some protection from light-induced degradation compared with unform
ulated B. thuringiensis, although the amount of protection was less th
an that provided by other experimental formulations.