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.
Jeanette is having trouble with wireworms in her potato patch and where she has grown yams.
Wireworms are larvae of Click Beetles. The larvae are shiny, brownish cylindrical creatures with 6 legs close to the head. They can grow to about 3.5 cm long, and are fond of eating roots, fleshy stems and tubers.
Wireworms can increase to pest proportions where sufficient crop rotation has not been practiced. The adults shelter in weeds or vegetable litter in and around garden beds.
To get rid of the adults, clear the garden area of weeds, old plants and mulch. You can then get the adults to shelter under a plank or bag laid on a garden bed. Early each morning, collect and destroy the beetles until it is obvious you have numbers under control.
Dig a 3 – 5 cm layer of compost into the top 15 cm of affected beds, or add plenty of organic fertiliser and grow a green manure crop to slash and dig into the topsoil when it is knee high.
Don’t grow yams, potatoes or carrots in that area again for at least four years. Rotate crops, starting with a legume, on a regular basis to prevent a build up of these pests in soil. (See Crop rotation )
Keep weeds under control and apply enough organic fertiliser to keep plants growing vigorously, and they should cease to be such a nuisance for you, Jeanette.
From e-mails I’ve received, it appears that some gardeners are having problems with their tomato plants. When tomato plants become water-stressed in prolonged hot, dry conditions that are affecting some parts of the country, they are prone to attack by fruit fly, heliothis moth caterpillars (corn earworm) and blossom end rot. Blossom end rot is caused by calcium deficiency, and is not a disease. Like us, plants need a good balance of calcium and magnesium to form a strong structure. Calcium and magnesium are required for growing tips of plants as well as fruit production and, if there are not enough of these nutrients to go around, growing tips will get priority. Calcium deficiency can occur in several different ways.
Most commonly, it occurs when soil is too acidic (soil pH less than 6) and there are insufficient calcium ions in the soil. Rarely, it also occurs in extremely alkaline soils (soil pH above 9) where calcium becomes insoluble, and plants are unable to absorb it.
In soils with a suitable pH of 6 – 7.5, erratic watering can cause it, as plants are unable to absorb nutrients from dry soil, when needed.
To avoid this problem, ensure that your tomato, capsicum or chilli bed has a suitable soil pH before planting out seedlings. See Changing soil pH. If your soil is slightly too acidic, and the problem has already occurred, you can raise soil pH slightly by dissolving a generous handful of dolomite (a mixture of calcium and magnesium) in a full watering can, and apply this around the root area (under mulch) of each plant – one full watering can per plant. If you know that your soil has plenty of magnesium, use agricultural lime instead. This treatment will take several weeks to work, so good bed preparation is worth the effort.
Tomatoes will benefit from being protected by a thick layer of mulch to reduce fluctuations in soil moisture, and a thorough soaking (under mulch) two or three times a week during dry weather, rather than a light daily watering. Avoid overhead watering of tomatoes.
Hot days increase transpiration (water loss) from plants in the same way we perspire to keep cool. Setting up a light shade cloth canopy over the tomato bed will reduce water loss from plants and help prevent water stress and sun scald on fruit. Tomatoes will ripen under light shadecloth in hot weather. A soil feeding of seaweed extract ‘tea’ can also help plants build resistance to adverse conditions, including drought.
Mosquito netting over plants will serve two purposes. It will prevent attack by Heliothis moth and fruit fly, and provide a light shade for the plants. Modern tomato varieties do not require insects for pollination. If older varieties cease to set fruit, flowers can be hand pollinated with a dry watercolour paint brush.
In some areas, the netting may be enough to slow transpiration, without the shade cloth. All fruit affected by grubs or caterpillars should be collected and fed to the chooks, or placed in a sealed black plastic bag and left in the hot sun. This will kill the larvae and break the breeding cycle. Never compost fruit that contains grubs.