P. Tamez-guerra et al., Spray-dried microencapsulated Bacillus thuringiensis formulations for the control of Epilachna varivestis Mulsant, SW ENTOMOL, 24(1), 1999, pp. 37-48
A new sprayable microgranule formulation of Bacillus thuringiensis subsp. k
umomatoensis (strain C-9) was evaluated for the control of the Mexican bean
beetle Epilachna varivestis Mulsant. Strain C-9 was isolated from dead E.
varivestis in a Phaseolus vulgaris L. field in Durango, Mexico. A spore and
crystal complex of the C-9 strain were active against E. varivestis larvae
in bioassays using treated bean plants (LC50 of 642 mu g/ml), and against
Trichoplusia ni (Hubner) larvae using artificial diets (LC50 of 219 mu g/ml
). The sprayable powder (microgranule formulation), consisting of cornstarc
h (CS), nixtamalized corn flour (NCF), vegetable oil, powdered sugar, 2-pro
panol, malachite green, and formaldehyde, was prepared using a spray-dry pr
ocess. Shelf life of formulated B. thuringiensis maintained over 90% of its
original activity after 24 months of storage. A field test demonstrated th
at treatments of formulated B. thuringiensis controlled E. varivestis signi
ficantly better than treatments with unformulated B. thuringiensis. This st
udy demonstrated that B. thuringiensis can potentially be formulated by spr
ay drying, based on ingredients, which would help to improve its activity a
s a biopesticide under field conditions.