Page 20 - Griffin Gazette Summer 2016

Bonus Getting to Know

Digital Content CEA

By Tami Van Gaal, GGSPro Technical wasps per 100 square feet if purely preventative and at 20
Support Representative wasps per 100 square feet when aphids are present.
Now that we know which Aphidius species to use and when
Applying calcium sprays to lettuce crops to release the wasps, we need to understand how to release
Several options can be used for foliar calcium sprays on the wasps. All parasitoids should be released under low-
lettuce. GGSPro’s preferred product choice is calcium chloride light conditions on the day they arrive. For Aphidius, remove
dihydrate because it provides calcium without any additional the vented cap and let all emerged wasps disperse in various
nitrogen, it leaves a minimal residue and it doesn't contain locations throughout the crop. Once the adults have left the
the blue indicator dye used in most formulated fertilizers. Mix container, replace the cap and place the vial in a location out
calcium chloride dihydrate at a rate of 0.5 oz per 3 gallons of direct light to let more emerge. Leaving bottles open in the
of water and apply with CapSil at ¼ tsp per gal. For larger greenhouse risks predation by ants. Repeat this until no more
volumes, mix 1 lb of calcium chloride dihydrate in 100 gallons of wasps hatch, usually a few days.
water and add 4 oz of CapSil. Alternatively, use straight calcium Remember that Aphidius are used as the foundation of an aphid
nitrate (15.5-0-0) for a foliar application. Apply at 300 ppm control program. Talk to GGSPro to learn more about how to
(0.25 oz per gallon or 27 oz per 100 gallon), with CapSil (see supplement Aphidius with other Aphidoletes aphidimyza or
rates above). lacewing larvae to control break-thru aphid populations.

Using Aphidius for aphid control in lettuce BCA, aphid mummy – Swollen aphid mummies (as seen in the top right
Aphid control with BCAs can be both relatively straightforward corner) indicate successful parasitism by Aphidius wasps.
and challenging. It's straightforward because the BCAs
themselves are relatively easy to release and recognize. BCA, Aphidius – Aphidius colemani serves as the foundation of BCA
However, aphid control can be challenging due to the high control for lettuce crops.
reproductive capacity of aphids, especially under warm
temperatures. Scouting for both the aphid and BCA populations
is critical to support rapid decision making and proactive
release. The foundation of a successful program focuses on the
use of parasitoid wasps.

Several species of Aphidius wasps are used to control aphids.
When the aphid species is known, the release can be targeted
to the pest species. For small aphid species, including melon,
cotton, peach and tobacco aphids, release Aphidius colemani.
For larger aphid species, such as foxglove and potato aphid,
release Aphidius ervi. Two strategies can be used when the
aphid species is not known: 1) assume that the most likely
aphid pests are small species, release A. colemani alone and
scout carefully for evidence of parasitism (presence of aphid
mummies) or 2) release a mix of A. colemani and A. ervi.

Success with Aphidius wasps requires that releases should
begin prior to aphid presence. Aphidius wasps do an excellent
job of preventing aphid establishment due to their ability to seek
aphids over a large space. However, they will not be effective
alone in stopping established aphid colonies. For this reason,
GGSPro recommends releasing Aphidius wasps on a biweekly
interval prior to aphid presence. When aphids are anticipated,
begin releasing Aphidius on a weekly basis. At first sign of aphid
presence, weekly releases should be in place. Release at 10