With the month being dry, growers have reduced fungicide sprays. This has also cut back on some insecticide sprays where we sometimes throw in an insecticide with the fungicide. It has been very obvious which orchards were treated with a broad spectrum insecticide – generally chlorpyrofos or pyrethroid. The only yellow aphid populations I’m seeing in Southeast GA is where an insecticide was used during May. Keep in mind our insect populations in early spring are not very high, as well as early season insect pests generally do not cause serious economic injury.
UGA Pecan Entomologist Dr. Angel Acebes and I visited the UGA Research (unmanaged) orchard last week and saw a good number of assassin bugs and parasitic wasps. In Ware County last week, I saw a lot of green lacewing eggs where aphids were present. Here are some photos of natural enemies to be on he lookout for.
Parasitic Wasps – Here is an egg parasitoid of stink bug that Angel found on stink bug eggs. You can just barely see her sitting on the eggs in the photo. This female wasp guarded these eggs while we held this leaf. She had already stung each egg, laying her egg and she was guarding them.
Parasitic Wasps of Aphids (A. Acebes): This group of wasps has a unique biology where they spend their immature stage inside their aphid hosts and the adults are free-living. A female wasp lays a single egg inside an aphid host. Once the egg hatches, the larva will feed inside the host, killing the host in the process. Parasitized aphids (mummies) turn black or brown depending on what kind of wasp has attacked them. If they are attacked by Aphelinid wasps, they turn black and if they are attacked by Aphediid wasps, they turn brown. Pecan aphids are most commonly attacked by Aphelinid wasps. Yellow pecan aphids and black-margined aphids parasitized by these wasps turn black, which can be misidentified as black pecan aphids. A way to check for this is by inspecting if the aphid moves once disturbed since mummified aphids are immobile and are glued to the leaves. Mummified aphids are also rounded and bigger than unparasitized aphids. Also, most of the time, black pecan aphids are found with dead yellow or brown spots on the leaves.
Assasin Bugs – We saw a good number of immature assassin bugs in Midville. They are in the same group of “kissing bugs” (Assissin bugs, wheel bugs, damsel bugs, leaf-footed bugs). They feed on soft-bodied prey like mosquitoes, flies, cucumber beetles and caterpillars.
Green Lacewing – In Ware County this week, I saw a good number of green lacewing eggs. The eggs are often found on plants and are easily recognized since they are attached to a long, slender silken stalk which holds them above the surface. The larvae are sometimes called “ant lions” and are predators. They eat many small insects as they grow ranging from leafhoppers, scale insects, mites and also aphids. This picture of an “ant lion” eating a sugarcane aphid on grain sorghum.
Lady Beetle – We actually didn’t see many if any lady bugs. Most folks know what to look for here; nonetheless, here is the larvae and pupae of a lady beetle. Larvae are usually carrot-shaped and sometimes called ‘baby alligators’. They are predatory and feed on a variety insects including mites, scales and aphids. To the right is the pupa stage.
Minute Pirate Bugs (A. Acebes): These predatory insects are very small measuring only between 0.04 to 0.08 inch (1-2 mm). They have piercing-sucking mouthparts just like the predatory stink bugs, and both nymphs and adults are predacious. They occur in high numbers on pecan trees feeding on aphids, thrips, insect eggs, mites and small caterpillars.
Predatory Stink Bugs (A. Acebes): Perhaps the trickiest predators to distinguish in the field are the predatory stink bugs since they normally resemble other plant-feeding stink bugs. A reliable method in telling them part is by looking at the mouthpart (straw-like stylet). Predacious stink bugs have broader and thicker stylets (twice the width of the antenna) and the first segment is not attached to the head except at the base. Plant-feeding stink bugs have narrower and thinner stylets (width of antenna and stylet are similar) and the first segment is attached to the head along its length. One of the most common predacious stink bug species is the spined soldier bug which resembles the plant-feeding brown stink bug except for the distinctly pointy ‘shoulders’. Predatory stink bugs prey on aphids, insect eggs and soft-bodied insects including caterpillars.
Authors: Andrew Sawyer and Angel Acebes-Doria