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Stink Bugs

Stink Bug plant damage

By: Sandy Feather ©2011
Penn State Extension


Q. I have extensive flower and vegetable gardens. Over the winter I was not much bothered by stink bugs in the house, and the first crop of raspberries was great, with not many adult stink bugs.  But then the onslaught began.  The first plants to be destroyed were some artichokes.  Then the hyacinth bean vines were totally decimated.  Following hard after was one of my butterfly bushes.  So far for they have not bothered my tomatoes, but the second crop of raspberries is completely demolished. The small nymphs seem to know which stems have fruit and congregate there.

When I realized what was going on, I began spraying them with a solution of Palmolive soap and some ammonia in water.  This does kill them but they still have severely damaged the cucumbers.  I am not too sure what the minimum amount of soap is that would do the job - maybe I am mixing it stronger than necessary. Do you know what strength would be sufficient to kill them? 

Using a 5-1 solution of ammonia and water kills slugs and does not damage plants so I figured some ammonia might help with the stink bugs. I have some traps now and adult bugs are being trapped but the smaller ones are still doing their incredible damage.  Is there anything else you might suggest for their control?
  

brown marmorated stink bug
Brown marmorated stink bug

A. Although brown marmorated stink bugs (Halyomorpha halys) were primarily a nuisance that invaded homes for the winter when they first arrived, we now realize what an important agricultural pest they are. Everyone from major growers to backyard gardeners have bee impacted by this pest in the states where it has been identified. Researchers from the United States Department of Agriculture, land grant universities such as Penn State, and state departments of agriculture are scrambling to find solutions to this growing problem.


Stink Bug Origins

Brown marmorated stink bugs (BMSB) are native to Asia and were accidentally introduced to the United States in the mid-1990’s, possibly as stowaways in a shipping container. They were first identified in Allentown, PA in 1998. They have made their way through the Mid-Atlantic States at a furious pace, with established populations in 36 states and the District of Columbia.


Identifying Stinkbugs

BMSB adults are varying shades of brown on both sides of their bodies, with light and dark bands alternating on their antennae and dark bands along the edges of their wings at the rear of their bodies. Mature insects are just under an inch long and have the “shield shape” characteristic of true bugs in the order Hemiptera. BMSB adults become active as weather warms in the spring, when they leave our homes and buildings to feed and mate outdoors. Their light green to white barrel-shaped eggs are laid in clusters of 25–30 on the undersides of leaves through the summer months.


Life Cycle

Eggs hatch in three to seven days, and the resulting nymphs (immatures) go through five instars (growth stages) to maturity. First instar nymphs are not very active and often remain close to the egg mass. It is possible that your observation that the nymphs seem to pick out the fruit-bearing stems on your raspberries is a reflection of where the eggs where laid. Nymphs are more brightly colored with reddish eyes and a yellowish-red abdomen with black stripes. Their antennae are like the adults’ – black with white bands. Nymphs range from pinhead size to almost one-half inch long.

BMSB affected by winter cold
Cold winters can affect populations


Plant Damage

BMSBs are proving to be a formidable pest of agricultural crops. They are known to damage apples, pears, Asian pears, peaches, plums, nectarines, apricots, raspberries, blackberries, blueberries, grapes, figs, tomatoes, peppers, eggplants, cucumbers, sweet corn, beans and peas in addition to soybeans and field corn. Numerous ornamental plants are also susceptible to attack from this pest, including maple (Acer spp.), catalpa (Catalpa spp.), eastern redbud (Cercis canadensis), yellowwood (Cladrastis kentukea), honeylocust (Gleditsia spp.), hibiscus (Hibiscus rosa-sinensis), tulip-tree (Liriodendron tulipifera), honeysuckle (Lonicera spp.), crabapple (Malus spp.), princess-tree (Paulownia spp.), plane-tree (Platanus spp.), black cherry (Prunus serotina), Yoshino cherry (Prunus x yedoensis), oak (Quercus spp.), rugosa rose (Rosa rugosa), lilac (Syringa spp.), elm (Ulmus spp.), and zelkova (Zelkova serrata). Damage has also been observed on herbaceous plants including cockscomb (Celosia argentea), spider flower (Cleome spp.), dahlia (Dahlia spp.,) sunflower (Helianthus annuus), zinnia (Zinnia spp.), and even some weeds such as burdock (Articum spp.).


Orchards

Sadly, BMSB is singlehandedly undoing decades of integrated pest management (IPM) in the orchard community. Researchers and orchardists have done an outstanding job of implementing IPM tactics, resulting in a 75 percent reduction in orchard pesticide use while successfully controlling traditional pests. BMSB could mean a return to cover sprays since they are active throughout much of the growing season. That means that insecticide sprays must be in place to protect crops throughout the growing season as well. Researchers are confident that studying this pest will result in effective controls for commercial growers as well as home gardeners. But they are not there, yet.

 

This past June, The United States Environmental Protection Agency (EPA) approved requests for a Section 18 emergency exemption for orchardists to use the insecticide dinotefuran to manage BMSB (these exemptions are granted on an emergency basis for products that are effective in controlling a given pest, but are not labeled for that purpose). The EPA also approved an insecticide that combines azadirachtin (neem) and pyrethrum for use by certified organic growers to manage BMSB on their crops. These exemptions underscore how seriously the agency takes the threat that BMSB poses to production agriculture.


Home Gardens

Unfortunately, there are not many options for home gardeners at this point. While the solution you applied to your plants may have proven effective at killing BMSB, it can also damage the plants you were trying to protect. This sort of damage is known as phytotoxicity (phyto=plant, toxicity=poisonous). Palmolive is a dish detergent meant to wash dishes. It likely contains wetting agents and degreasers that have a tendency to damage plants. Although ammonia contains the plant nutrient nitrogen, too strong a solution can also damage plants. It would be fine to place this solution into a container and knock BSMBs into it, but it is risky to spray it on plants that you value.


Stink Bug Control

There are soaps that have been created expressly to control insects on plants, generally known as insecticidal soaps, including Safer® Brand and Concern®. Even they can cause phytotoxicity when applied to certain plants that do not tolerate it well, or if it is applied when it is too hot and humid. If you want to spot spray insects on plants, choose one of these products instead of the Palmolive and ammonia solution. Pyrethrum, an insecticide made from the flowers of the pyrethrum chrysanthemum, also shows promise for home gardeners. Both insecticidal soap and pyrethrum are more effective on nymphs than adults. Neither has significant residual activity. Insecticidal soap is no longer effective once the sprays have dried; pyrethrum breaks down within 3-5 hours of exposure to sunlight.


Rescue Stink Bug Trap

Traps for BMSB management are still under investigation. Researchers are looking at light traps and pheromone traps (pheromones are chemical substances that insects use to communicate with others of their kind). If experience with Japanese beetle traps can serve as a guide, the BMSB traps that are available now should be placed away from the plants you want to protect. Placing the traps near vulnerable crops can result in a higher BMSB population than you might have otherwise.


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