Joanne in S.A. is having problems with budworms attacking her roses. Budworms are caterpillars of the Helicoverpa moth family (previously called Heliothis moths). These destructive pests also attack stressed plants of sweet corn, tomatoes, a range of other fruits and vegetable plants and ornamentals.
The moths lay their eggs at night on young foliage close to fruits or flower buds and the young caterpillars feed on the foliage first before moving into buds or developing fruits. After several weeks of feeding, the caterpillars burrow into the topsoil beneath the plant and pupate until rain that produces a burst of new plant growth will signal an opportune time for adult moths to emerge from pupa cases and lay eggs. If you netted plants after the first moth attack, they won’t be protected from further attacks because the pupating moths will be inside the netting.
The first thing to do is remove all damaged buds, fruits/vegetables and caterpillar-infested young foliage and give them to the chooks or dispose of them in a sealed plastic bag – not in the compost heap. Then spray young foliage near buds and fruit with a registered organic treatment that is effective against this moth larvae. Nature’s Way Caterpillar Killer and Naturalyte Insect Killer are a couple of examples. Check daily for individual eggs laid on young foliage and respray when necessary, or after rain. The caterpillars have to be controlled before they enter buds or fruit where the sprays are not effective.
Although rain stimulates egg laying, we have found that this moth only lays eggs on plants that have had a period of water stress. Plants can only absorb the elements they need for pest-resistance from damp soil, and water stress provides the conditions that make them susceptible to attack from this and other pests. Where water is in short supply, apply a 5 cm layer of mulch around your plants and use an upturned 2 litre plastic container with the base removed and the neck embedded into the top soil to apply water efficiently, directly to the root area of plants (see photo). After rain, give plants a drink of organic seaweed extract tea to assist in building disease-resistance.
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.
Following my post on organophosphates and ADHD, one of my blog readers asked for more information about derris dust (rotenone) that has been popular with organic gardeners for pest control as rotenone is an organic pesticide made from the roots of a tropical plant. It also has a long history as a piscicide (fish killer).
Rotenone works by shutting down energy production in cells, which makes it a neurotoxin. Research linked it with Parkinson’s Disease, but this was largely discounted as the rats in the research had rotenone injected directly into their brains, which is not a very fair trial.
In 2007, the USEPA published a Re-registration Eligibility Decision (RED) assessing only the risks of contact from its use as a piscicide (i.e. swimming in or drinking treated water). The RED stated that small children and foetuses were more susceptible to the effects of rotenone. www.environmentalhealthnews.org/ehs/blog/health-ecosystem-effects-of-rotenone-ignored
According to Environmental Health News, researchers have found that rotenone selectively destroys dopamine-producing cells in petri dishes. (The full document on this research must be purchased).
In 2010, another study was published about research in mice that showed a progression of Parkinson’s-like symptoms after mice were fed low doses of rotenone over a period of time. The research found that concentrations in the central nervous system were below detectable limits, yet still induced Parkinson’s Disease pathology.
Australia’s APVMA has reviewed rotenone and decided that it can still be used as a pesticide. However, both Canada and the United States are phasing out the use of rotenone for everything except its use as a fish poison. In Canada, for example, rotenone could not be sold for livestock, gardening, or domestic pet use after the end of 2008, and existing stocks can’t be used after the end of 2012.
I certainly don’t recommend the use of Derris dust, but gardeners must make their own evaluations of this pesticide.
Earlier this week, ‘Today’ program on Channel 9 aired a segment about new research showing a link between organophosphate pesticides and ADHD. The research involved 1,139 children between 8 and 15 years and found high levels of organophosphate metabolites in urine of children with ADHD. This link is not surprising as organophosphates (and carbamates) are neurotoxins. These pesticides work by affecting the central nervous system, and organophosphates were developed for chemical warfare before being used as pesticides.
Both organophosphate and carbamate pesticides block the action of the enzyme acetyl cholinesterase, which regulates the transmission of nerve messages. Well-established research has shown that chronic exposure to organophosphates induces neurological dysfunction. Children are more susceptible to all toxins, including neurotoxins.
Separate research has linked pesticide exposure with Alzheimer’s disease and Parkinson’s disease. Included in the suspects is the very popular Derris dust, which has also been found to be a neurotoxin.
‘Today’ presenters advised that all fruits and vegetables should be carefully washed before eating. Good advice to be sure, but advice that misses the point that some organophosphate pesticides commonly used on food plants are systemic. Systemic pesticides enter the sap system in plants, are distributed to all parts of the plant, and can’t be washed from our food. As a lot of our food is now imported from countries with differing standards for pesticide regulation, we have no way of knowing whether or not our food contains systemic organophosphates. AQIS carries out testing on only a tiny percentage of imported foods.
Write to your federal Member of Parliament requesting a ban on the use of systemic organophosphate pesticides in local produce, and improved inspections and standards for imported foods. Remind your Member of the cost to the community in treating the problems caused by these pesticides. Where possible, buy organic produce for your children, and grow as much as you can using organic methods. It will not only be healthier – you will notice it tastes better, too.
In hot, dry weather the 26 or 28-spotted ladybirds can do a lot of damage to the vegetable patch. Plants can only absorb nutrients from the soil as water-soluble ions. As soil dries out, vegetable plants are unable to absorb the nutrients they need to produce the compounds that deter pests, and these troublesome ladybirds can move in, feeding on leaves until only a network of veins remain. The larvae (pictured below) tend to feed on the underside of leaves while the adults feed on the upper sides of leaves. Badly damaged eaves can become papery, and brown. Their favourite foods are the cucurbit or squash family, which includes the melons. They can also attack, bean, potato and tomato plants.
The problem with using sprays to get rid of these pests is that whatever will kill them will also kill the beneficial ladybirds that help keep many garden pests under control, including the bright black and yellow ladybird that eats powdery mildew and other fungi. Fungus-eating ladybirds are often seen wandering over leaves of the squash family.
The Brisbane Insects website now has a field guide to ladybirds to make it very easy for you to identify whether the tiny creatures crawling on your plants are pests or ladybird larvae, which come in a range of colours and shapes.
Click here: Ladybird Field Guide
The best way to solve the problem of 26 (or 28)-spotted ladybirds is to knock the adults and their larvae into a soup tin with some methylated spirits in the bottom of it. Also scrape off the eggs, which can be found in a cluster on the underside of leaves (see photo below).
Then give the foliage and soil around the plants a generous drink of seaweed extract tea, to supply potassium and trace elements plants need to build resistance to pests, because only stressed plants are attractive to pests. Ensure the plants have sufficient fertiliser for healthy growth, and that the soil is not too acidic or too alkaline. Water the plants thoroughly, under mulch, when the top cm. of soil is dry, rather than giving them a lighter, daily watering. If drought conditions are making it difficult to spare enough water, you can help deter them by spraying both sides of the leaves with chilli spray, but you will need a lot of chillis. The solution is – 2 cups chillis to 2 cups of water. Chop chillis finely while wearing gloves. Steep them in water for an hour, strain mixture, and spray liquid over leaves. (Garlic spray can be used as a deterrent but breaks down quickly in hot weather.) Finally, get rid of any blackberry nightshade plants. These act as a host for this little pest. See:Blackberry Nightshade Eggs and larvae of the 26 (or 28)-spotted ladybird.
Temperatures between 11-28° C. and excess humidity (without rain) can provide suitable conditions for powdery mildew spores to become active, especially on plants have been affected by drought, or are under-fertilised.
Powdery mildew spores are carried by air and, once active, will continue to spread in dry conditions. This fungal problem affects a wide range of fruit, vegetable and ornamental plants. In most plants, it shows as a dusting of grey-white powder on foliage, and distortion or puckering of new leaves. The infection often begins on the underside of leaves. On mangoes, fruit develops brown to purple patches, and grey patches on papaws. Apples develop light lines across the surface of fruit.
Preventative spraying with wettable sulphur is not recommended because sulphur is damaging to beneficial insects that keep pests under control, and a pest outbreak will often occur after spraying or dusting with sulphur. Sulphur will also damage plants if applied to plants that are short of water, or when temperatures are above 30° C.
Powdery mildews are usually caused by Oidiumspp. fungi, and can be controlled by organic powdery mildew treatment or applications of German chamomile tea. For each 500 ml of spray required, steep one teabag in a cup of boiling water for 15 minutes, then dilute to 500 ml with cold water. Remove and destroy severely affected leaves, then spray the rest of foliage early in day so that leaves have time to dry before nightfall. Don’t forget to spray both sides of leaves.
Powdery mildew is common where plants are deficient in potassium and some trace elements, as when the plants have exhausted their supply of fertiliser, or when they cannot absorb nutrients because soil is too dry. Seaweed extract is rich in both potassium and a range of trace elements (including sulphur), and spraying foliage with seaweed tea can be effective against powdery mildew, not because it kills the fungi, but because it quickly provides the nutrients plants require to resist these fungi.
To avoid this problem in future, ensure that fruits and vegetables have adequate complete fertiliser to last them through harvesting, including an annual application of seaweed extract tea to soil around plants. also ensure that they receive adequate water for steady growth but avoid overhead watering. It is difficult for some gardeners to understand that good cultivation practices can prevent pest and disease problems but it is true. The pea plants in the photo only developed powdery mildew after I had collected pods for seed and I had ceased to water them.
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.
If you come across a cluster of small, yellow cocoons on leaves of Brassica vegetables – don’t spray them or feed them to the chooks. They do not belong to garden pests. (See photos below.)
These cocoons are, in fact, the pupation stage of a very small, black wasp. This wasp belongs to the Braconidae family. Braconids are parasitic wasps and very beneficial insects to have in your garden.
The female adult wasps, which are barely 5 mm long, lay their eggs in caterpillars of the Cabbage White Butterfly, which feeds on the leaves of stressed broccoli, Brussels sprouts, cabbage, cauliflower, horseradish, kale, radish, rocket, swedes and turnips.
The wasp larvae then feed on the caterpillars from the inside until they are ready to pupate. (Sounds gruesome, doesn’t it.)
They each then spin a small cocoon on the remains of the caterpillar, and hatch out two or three weeks later to repeat the cycle.
Adult wasps feed on nectar from flowers. It is worthwhile growing some nectar-producing plants to encourage these useful pest predators.
These flirtatious little butterflies can be destructive to stressed Brassica plants.
Sowing dill seed between brassicas can deter these pests as the aroma from dill confuses them. If you see these butterflies around your brassica plants, attach the plastic clips from packaged bread to the edges of some of the leaves as a pest deterrent. They look as though pests are already laying eggs on those plants. Use white clips for butterflies, beige for cabbage moth.
If your plants have been attacked, squash any green caterpillars or feed them to the chooks. They often hide along the mid ribs of leaves making them difficult to see. Check daily for newly laid CWB eggs (bright yellow dots – usually on the backs of leaves), and brush them off. Also check for newly hatched larvae – these appear as fine green threads hiding under the leaves, and can look like leaf veins.
White cabbage butterfly or cabbage moth attack is a sign that either:
1) Your plants could do with more water. Brassicas need thorough, regular watering – not a daily sprinkle. Mulching the bed reduces water loss and encourages horizontal movement of water through soil.
2) You have been a bit mean with the complete fertiliser when preparing the bed. Brassicas prefer a humus rich soil to provide a good supply of fertiliser. If they are not making steady growth, a side dressing of compost (under mulch) or applications of complete fertiliser, applied as a tea, can correct the problem. Or, they are missing some essential trace elements that you can supply with a drink or two of good quality seaweed extract tea (such as Acadian, Natrakelp or Seasol).
3) You have added enough fertiliser but the soil is too acid or alkaline for the plants to absorb what they need for pest resistance. If it is a case of too acid – and this can be remedied with an application of dolomite or agricultural lime. If you suspect acidity, apply a handful per square metre of bed and water it in. Avoid using hydrated lime on beds that contain plants as it can burn plant roots. If your soil is too alkaline, the addition of elemental sulphur will reduce alkalinity.
However, if they are making a total mess of your plants, apply Dipel while waiting for soil conditions to improve. Dipel will kill the caterpillars without killing good insects.
Although bean crops in most areas are close to the end of their productive life (April-May), some gardeners in warm climates are having problems with bean fly.
The best way to avoid bean fly is to have plenty of compost in the bed where you grow your beans so that they will have a full range of nutrients available to them. These pests tend to attack plants that are low in potassium. A drink or two of seaweed extract tea can help bean plants that have been attacked because it has plenty of potassium, as well as trace elements that plants need for good health. But don’t overdo the seaweed as too much can “lock out” some other nutrients.
Also, hill up soil around the main stem of the bean plants to encourage them to send out more roots along the stem above the damaged area just above ground level. Mix some compost through the hilled-up soil. Plants can be saved this way. Also, allow a three year break between growing crops of beans in the same soil.
Bean fly love warm, humid weather. In these conditions put out some yellow sticky paper traps to alert you to their arrival, and hopefully catch some of the adults before they lay eggs. Also look out for fine lines on leaves and stems indicating where the larvae have tunnelled to reach the base of the stem. Stems of affected plants become swollen, cracked and reddish in colour.
Organic sprays are not really effective because the larvae that do the damage are protected by plant cells. A good fertilising and watering routine will help your plants avoid these pests.