Stink bugs – update

stinkbug2 An environmentally-friendly way of getting rid of stink bugs is to use a stick to knock them into a container with some methylated spirits in the bottom of it, so that you don’t have to come in direct contact with these smelly bugs that change colour from green to orange to brown-black as they grow.
However, a reader e-mailed me this week about his problem with lots of stink bugs on his orange tree that is too tall to use this method, and he wanted to know if he could spray the tree with metho, instead.

Spraying the bugs with methylated spirits would only further damage the tree. If you also have a tree affected by bronze orange bugs (stink bugs), these bugs are a sign that a tree is very under-nourished. It is probably extremely water-stressed, as plants can’t absorb nutrients from soil if it is not damp enough for the minerals to become water-soluble. Give the soil around the affected tree a thorough watering, then give it an application of complete organic fertiliser and then water in some organic seaweed tea. You haven’t said which climate area you live in. If you live in an area where water shortages are common, keep the tree pruned to a size where it can remain healthy on the amount of water that you and nature can provide.

Bronze orange bugs or stink bugs and harlequin bugs are sap sucking pests that can do a lot of damage to stressed citrus trees. Spined citrus bugs suck sap from fruit. Before dealing with these bugs, you need to don old clothes, sturdy shoes, gloves and goggles or sunglasses as bronze orange bugs eject a corrosive fluid with a vile smell when they are threatened.
Young bugs tend to cluster under the lower leaves of the trees and are easy to get at, but if trees are too large for knocking them into a tin, spread some large sheets of plastic under the tree, then use a broom stick or long pole to give the foliage a good shake and, when they drop to the ground, either squash them, or gather up the plastic and slide them into a large container with a suitable pest treatment in the bottom.
Organic-registered products such as Natrasoap (not ordinary soaps or detergents) or Eco-oil will kill these pests but they should not be used on heat-stressed or water stressed plants, or in high temperatures. However, either of these products can be used to spray stink bugs when they shelter around the base of the tree on hot days. Harlequin bugs like to shelter in weeds, and they can be sprayed where they are hiding. Get rid of weeds, particularly along fence lines to prevent re-infestation.
However, the best way to avoid these horrible pests is to take good care of your citrus trees.

Stink bugs

The flat-bodied bronze orange bugs in the photos below are also known as stinkbugs because of the vile odour of the secretion they release when disturbed. These bugs can do a lot of damage to citrus trees as they suck sap from new shoots and flower stems, causing shoots to wither, and crop losses. The secretion is very caustic and can burn foliage. Stinkbugs are commonly seen on citrus trees from winter onwards where a prolonged dry spell has caused water stress.
The young nymphs are green, (about 6 mm long) and can be found in groups on the underside of leaves. As they grow to adults, they can reach 2.5 cm in length, and change in colour through grey-green, to orange or pink-orange, to almost black. Older nymphs and adults are more obvious, clinging in groups to upper surfaces of foliage.
No organic sprays or treatments seem to be effective for these pests. We have found the safest organic way to remove them is to don some goggles or sunglasses and some long rubber gloves (to avoid the secretion burning or staining your skin), and then use a stick to knock them into a fruit tin containing some methylated spirits. It is best to de-bug your tree/s before the weather becomes too warm as, on hot days, the bugs leave the foliage and congregate around the base of the tree. The bugs will die off in hot, dry weather but by then they will have done a lot of damage.
Some gardeners use a vacuum cleaner to remove stinkbugs, but this method is only practical if your cleaner uses disposable paper bags so that you can dispose of the critters in a sealed bag, and if your vacuum cleaner and extension leads are suitable for outdoor use.
In summer, have a look under citrus leaves for stinkbug eggs. The eggs are spherical and fairly large for insect eggs (3 mm), and they are laid in rows. Remove the leaves carrying eggs and dispose of them in a sealed bag.
To prevent future attacks, make sure your citrus trees receive adequate water and are mulched to keep soil moisture more consistent. Also check that soil pH is between 6 and 7, and that your trees have received adequate complete fertiliser for best pest resistance.

The Brisbane Insects website has a lot of photos of stinkbugs (a.k.a. bronze-orange bugs) at all stages of their life cycle, including one of their mating position, and a close-up of exactly which part of their body releases the vile liquid.

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