Biodegradable Insecticides in Forestry
179
insecticidal materials, persistence within the living tissue for periods of time
sufficient to allow the toxicant to translocate and accumulate in the photosynthate
sinks (areas of new growth), selective cholinergic or other toxic mechanisms of
sufficient strength to kill the insect by ingestion, and availability of candidate
toxicants.
Xylem-mobile systemic insecticides can be applied by soil application (Brown
and Eads, 1975), trunk injection (Brown and Eads, 1975; Merkel, 1970), trunk
implantation (Brown et al., 1979), or bark painting (Johnson, 1965; Moody et
al., 1976, 1977a,b; Ragenovich and Coster, 1974). Some xylem-mobile insecticides are aminocarb (Sundaram and Hopewell, 1976, 1977), dimethoate (Crafts
and Crisp, 1971; Johnson, 1965), carbofuran (Solomon and Oliveria, 1977), and
acephate (Sundaram and Hopewell, 1976; Sundaram et al., 1977).
Trunk implantation of systemic insecticides shows promise for protecting
high-value trees that produce cone crops for seed used in regeneration (Merkel,
1970.) Methamidophos, dimethoate, oxydemetonmethyl, and dicrotophos provided prophylaxis for up to 6 months or more in slash pine. Future studies in
this area will make use of implants, where the unformulated, water-soluble,
technical-grade insecticide is encapsulated and placed under the bark for slow
release. Implant treatment strategies have been successful in suppressing Jeffrey
pine needle minor [Coleotechnites near milleri (Heinrich)] (Brown et al., 1979).
Acephate implants provided protection for up to 6 weeks.
The persistence, distribution, and translocation of acephate in spruce trees
shows that the insecticide is very xylem mobile and is degraded in approximately
14 days (Sundaram and Hopewell, 1976; Sundaram et al. 1977). Acephate is
phloem mobile when applied to photosynthate sources (foliage) on 15-year-old
Jeffrey pine trees with strong photosynthate sinks (Crisp et al., 1979). Approximately 5% of the applied dose translocated through the phloem to the new
growth after treatment of the previous year's foliage. Methamidophos, a metabolite of acephate, was also detected in the sinks. This observation was reported
earlier in spuce trees (Sundaram et al., 1977).
Acephate would seem to have the potential to protect the new growth from
defoliation by the early instar western spruce budworm (Brewer and O'Neal,
1977; Richmond et al., 1978). Two factors are critical if an early spray strategy
is to be successful-timing of the application and spray volume. The systemic
insecticide needs sufficient volume to allow cuticular penetration and absorption
to occur over a thoroughly wet surface.
Aminocarb translocation was characterized in potted conifers as weakly
xylem mobile (Crisp, 1972). Field studies confirm this mobility (Sundaram,
1978; Sundaram et al., 1977). It is apoplastic in white spruce [Picea glauca
(Moench)]. Aminocarb persisted in trace amounts for periods up to 64 days
postspray.
The fate, persistence, and translocation of fenitrothion in conifers and some
179
insecticidal materials, persistence within the living tissue for periods of time
sufficient to allow the toxicant to translocate and accumulate in the photosynthate
sinks (areas of new growth), selective cholinergic or other toxic mechanisms of
sufficient strength to kill the insect by ingestion, and availability of candidate
toxicants.
Xylem-mobile systemic insecticides can be applied by soil application (Brown
and Eads, 1975), trunk injection (Brown and Eads, 1975; Merkel, 1970), trunk
implantation (Brown et al., 1979), or bark painting (Johnson, 1965; Moody et
al., 1976, 1977a,b; Ragenovich and Coster, 1974). Some xylem-mobile insecticides are aminocarb (Sundaram and Hopewell, 1976, 1977), dimethoate (Crafts
and Crisp, 1971; Johnson, 1965), carbofuran (Solomon and Oliveria, 1977), and
acephate (Sundaram and Hopewell, 1976; Sundaram et al., 1977).
Trunk implantation of systemic insecticides shows promise for protecting
high-value trees that produce cone crops for seed used in regeneration (Merkel,
1970.) Methamidophos, dimethoate, oxydemetonmethyl, and dicrotophos provided prophylaxis for up to 6 months or more in slash pine. Future studies in
this area will make use of implants, where the unformulated, water-soluble,
technical-grade insecticide is encapsulated and placed under the bark for slow
release. Implant treatment strategies have been successful in suppressing Jeffrey
pine needle minor [Coleotechnites near milleri (Heinrich)] (Brown et al., 1979).
Acephate implants provided protection for up to 6 weeks.
The persistence, distribution, and translocation of acephate in spruce trees
shows that the insecticide is very xylem mobile and is degraded in approximately
14 days (Sundaram and Hopewell, 1976; Sundaram et al. 1977). Acephate is
phloem mobile when applied to photosynthate sources (foliage) on 15-year-old
Jeffrey pine trees with strong photosynthate sinks (Crisp et al., 1979). Approximately 5% of the applied dose translocated through the phloem to the new
growth after treatment of the previous year's foliage. Methamidophos, a metabolite of acephate, was also detected in the sinks. This observation was reported
earlier in spuce trees (Sundaram et al., 1977).
Acephate would seem to have the potential to protect the new growth from
defoliation by the early instar western spruce budworm (Brewer and O'Neal,
1977; Richmond et al., 1978). Two factors are critical if an early spray strategy
is to be successful-timing of the application and spray volume. The systemic
insecticide needs sufficient volume to allow cuticular penetration and absorption
to occur over a thoroughly wet surface.
Aminocarb translocation was characterized in potted conifers as weakly
xylem mobile (Crisp, 1972). Field studies confirm this mobility (Sundaram,
1978; Sundaram et al., 1977). It is apoplastic in white spruce [Picea glauca
(Moench)]. Aminocarb persisted in trace amounts for periods up to 64 days
postspray.
The fate, persistence, and translocation of fenitrothion in conifers and some