Optimizing Augmentative Releases Of Lacewing Eggs

FROM: AG CONSULTANT

Introduction

Consultants must provide customers with information and advise about the use of numerous products and diverse strategies. The quality of products and means for their effective implementation are directly related to cost-effectiveness, and are therefore of upmost importance to recommendation decisions. The purpose of this article is to provide information to consultants about optimizing delivery of eggs of a commercially available green lacewing, Chrysoperla rufilabris, to reduce target pest populations.

Chrysoperla rufilabris is utilized as a natural enemy of many soft-bodied pests, including aphids, leafhoppers, and mealybugs, on a wide variety of plants in diverse plantings, such as grapes, citrus and interior plantscapes. The larval stages of this lacewing are solely and voraciously predatory. Feeding is accomplished by seizing pests with hollow, pincer-like jaws and sucking the prey's body fluids. Implementation of augmentative releases is achieved by delivery of either pre-fed larvae or the eggs of this predator to affected plantings.

The use of pre-fed larvae is particularly suited for situations where pest populations are incipient and localized; where aesthetic injury from relatively small pest populations could prove costly; and where all developmental stages of pests, such as aphids, occur. Pre-fed lacewing larvae in specified quantities are available in dispensers for ready hand-delivery. Care and delivery instructions for the pre-fed larvae are provided with the dispensers.

The lacewing egg stage is a desirable product for many situations because eggs are inexpensive, allowing large numbers to be released, and they can be delivered using a variety of methods. Eggs can be delivered to plantings in dry media that can be broadly dispersed, or placed in specific locations either on cards or in small containers. Eggs can also be delivered in liquid media, allowing the use of new application methods such as mechanized sprayer systems that incorporate carrier/stickers that adhere the eggs to target plants. Further, eggs are more readily handled and shipped because they are not mobile and large quantities require little space.

When lacewing eggs are utilized, it is paramount to successful implementation that their delivery to the target planting coincides with complete development of lacewing larvae within the eggs, and with the availability of susceptible developmental stages of pests for prey. These two factors provide the best assurance that lacewing larvae will both hatch and locate prey quickly following delivery. Egg membrane color and color patterns of the developing lacewing larvae within the eggs can be used to predict when larvae will hatch.

Lacewing eggs undergo a series of color changes as the developing larvae grow. When eggs are first deposited by adult lacewings, they are bright green; as the larvae develop the egg membrane becomes yellow-green (Figure 1), and then dull yellow. The eggs then become dull gray (Figure 2); when this stage is reached the larvae are also gray, and distinct larval eyespots and abdominal bands can be seen with a 14X hand lens and/or a dissecting microscope. When most of the eggs display these characteristics, hatching will be nearly complete within 12-15 hours. Egg membranes from which larvae have eclosed are ghostly white (Figure 3) and are good indicators that hatch has begun.

The quality of lacewing eggs that come from the insectary is absolutely crucial to syncronized larval eclosion. Eggs shipped to customers that have been processed through carefully managed environmental and quality controls will be syncronized to hatch within the 12-15 hour period.

Beneficial Insectary recommends the following four criteria as the best means to determine that Chrysoperla rufilabris eggs are ready for immediate release: 1. egg membranes are dull gray; 2. abdominal bands of larvae are distinct; 3. larval eyespots are readily visible; and 4. at least 1% of the eggs have hatched (see Figures 2 and 3).

When ordering lacewings it is necessary to first specify the purchase of pre-fed larvae and /or eggs. Because the release of optimally developed lacewing eggs can be accomplished in both dry and liquid mediums, it is necessary to specify the intended delivery method. If a mechanical liquid sprayer system is to be used, refer to the mixing and application instructions provided by the manufacturer.

When a shipment of lacewing eggs is received, the package should be immediately opened and inspected. Quality controls and careful packaging and shipping procedures will assure that most of the eggs will be dull yellow and gray, and that subsequent egg hatch will be syncronized. Eggs should be held at about 75° F(± 5°) and at least 50% RH until time of delivery. If release must be delayed, we recommend the eggs never be held below 60° F or 50% RH to retard larval development. We further recommend that eggs never be held more than three (3) days at these cooler conditions. Immediately prior to release the eggs may be held at 60° F for a very short period, 1-2 hours, during transport to the field.

For more information and to receive a fact sheet on Optimizing Applications of Chrysoperla rufilabris Eggs, please contact BENEFICIAL INSECTARY at 1-800-477-3715 or at toll free fax 1-888-472-0708.

Fig.1. Yellow-green lacewing eggs.

Fig.2. Gray lacewing eggs showing abdominal bands and eyespots of larvae.

Fig.3. Ghostly white egg membranes of hatched eggs.

M. Rose, Science and Education Advisor, Beneficial Insectary, and Research Scientist, Montana State University, Bozeman.

R.K. Morrison, former Director of Research and Development, Beneficial Insectary, Redding, California

S. Penn, President, Beneficial Insectary, Redding, California