Papaya mealybug – a new invasive pest

About Papaya mealybug

Papaya mealybug is a new invasive pest that was first recorded in the Northern Territory in July 2023.  It has now also been widely observed in and around the greater Brisbane area.  It is an aggressive mealybug that attacks many plant species including papaw, frangipani and hibiscus.

High numbers of this pest will cause sticky secretions, sooty mould (a black fungal growth) and leaf drop.  Plant dieback and death are ultimately possible if unchecked.

Papaya mealybug on frangipani. (image N.T. Gov’t)

While this is a very nasty mealybug that found its way to Australia inadvertently we are fortunate on two counts.

  1. Australia is home to a native species of mealybug-feeding ladybird that is commonly known as ‘the mealybug destroyer’ or more precisely as Cryptolaemus montrouzieri (Cryptos for short).
  2. A tiny wasp parasitoid called Acerophagus papayae (with no common name) seems to have ‘piggybacked’ its way to Australia along with the mealybug.  This tiny wasp is proving to be a useful biological control agent of Papaya mealybug and has been deliberately released into several countries as this pest has made its way around the world.

The tiny beautiful parasitoid wasp Acerophagus papayae (Image N.T. Gov’t)

Control options for papaya mealybug

We know already from experience that while some soap and oil sprays may help reduce numbers of the mealybug, pesticides are not very effective and generally make the situation worse. This is because of their negative impact on beneficial insects.  Encouraging biological control agents to do the job for you is the more sustainable and rewarding approach.

A combined effort from ladybird beetles, parasitoid wasps, lacewings and hover flies will be the best strategy.

Our mealybug destroyer

Bugs for Bugs have been producing Cryptolaemus ladybird beetles now for more than 40 years.  These proven performers can be released to compliment your beneficial insect population in the battle against mealybug.

Cryptolaemus adult ladybird beetle – the ‘mealybug destroyer’ (Image Graphic Science)

Fruit fly – how can you manage a difficult pest?

Fruit flies are active – don’t get caught out!

If you wish to grow fruit then you need to be thinking about managing fruit fly.

Your fruit are most at risk when:

  • Conditions are warm
  • There have been recent rainfall or shower events
  • You have ripening fruit susceptible to fruit fly attack

Pesticide sprays are not the best option

In the past cover sprays have been used to control fruit fly.  The chemicals used to kill fruit fly are toxic to beneficial insects and this invariably leads to other pest problems.  They are also not good for human consumption and should be avoided.

A systems approach for managing a difficult pest

We endorse a multi-pronged approach to protect your crop from fruit fly:

  • Monitor the fruit crop by using fruit fly traps and also inspect regularly for any evidence of damage or fruit fly activity.  If the conditions described above apply then you should be actively practicing fruit fly control.
  • Regularly apply protein bait sprays to attract and kill fruit fly before they are able to sting your fruit
  • Place MAT cups to suppress the male fly population
  • If you have backyard fruit trees you might do best to use netting to protect your fruit from attack

Our fruit fly toolkit

We have put together the elements of fruit fly management into an easy-to-read brochure.  Download your copy here.

Strawberry bronzing review

This season many growers and agronomists have been finding higher than normal levels of bronzed fruit and there is concern that this bronzing is the result of thrips activity. However, on the farms that Bugs for Bugs crop scouts visit regularly thrips numbers are much lower than what is normally associated with the levels of bronzing being observed. A proportion of this early season bronzing may be attributed to aphids. However, it is difficult to associate most of this bronzing to either thrips or aphids and we believe that environmental conditions have been the main contributing factor.

A considerable amount of research has been conducted in the United States on the causes of bronzing in strawberries. Researchers conducted an extensive study into bronzing in California, where it was being attributed to thrips. They found that only a small proportion of the damage was due to thrips and the majority was a result of environmental conditions. A separate study conducted in Iowa attributed less than 1% of fruit bronzing to thrips despite thrips levels exceeding recognized EILs.

Three distinct types of bronzing have been identified as affecting strawberry fruit, and they are termed Type I, Type II and Type III bronzing.

Type I bronzing

Type I bronzing is the only form of bronzing that is associated with insect pests, primarily thrips. It is localized to areas of the fruit that have been directly feed upon by the pest. This is usually the area under the calyx and the areas outside the indentations formed in the fruit tissue around the seed.

Type II bronzing

Type II bronzing is attributed to chemical burn and is normally associated with the use of pesticides containing sulphur, or other caustic compounds in unfavorable weather conditions. This damage is also localized in nature and is confined to the area directly contacted by the chemical.

Type III bronzing

Type III bronzing is caused by certain environmental conditions, primarily high temperatures, low humidity and high levels of solar radiation. Unlike other types of bronzing, it affects the whole fruit. It is thought to begin in early fruit development when epidermal cells are damaged, resulting in a loss of integrity in the cuticle and epidermis. As the fruit develops and ripens, the bronzing may become less pronounced but the fruit has a dull appearance, texture can become rubbery, and shelf life is reduced. There appear to be differences in susceptibility amongst verities, with lighter coloured fruit being more susceptible than darker fruit. Thrips are often mistakenly blamed, but researchers have found no link between thrips activity and Type III bronzing. At times, this type of bronzing will result in significant reductions in marketable yield.

Researchers have identified environmental conditions and production practices that will have an influence on incidence levels. In California, lower levels of bronzing occur in coastal regions, where regular sea fogs moderate temperature, humidity and light levels. When misters or micro sprinklers are used during peak periods of the day incidence is reduced again due to moderation of temperature and humidity. Pesticides (fungicides or insecticides) applied shortly before periods of high risk also reduce incidence. This is thought to be a result of the sulphinated lignins contained in many pesticides, which are known to provide protection against solar radiation.

Researchers see this type of bronzing as primarily a problem from spring to mid-summer in California and attribute this to a lack of canopy development at this stage of the season. Later in the season a more developed canopy will provide greater moderation of the micro-climate. Increased incidence has also been noted with later plantings, and this has been attributed to reduced canopy development.

Given the generally mild conditions that South East Queensland has experienced so far this season, it is reasonable to question why Type III bronzing would be such an issue. However, during the 2000-2001 strawberry season in the Central Coast region of California there was a significant outbreak of bronzing while researchers were investigating its causes. During this period temperatures at harvest were generally between 15-25 °C with only two days over 30 °C, and peak day solar radiation levels that are comparable to those experienced in South East Queensland this season. It is possible that the combination of a relatively warm and dry autumn, late planting and generally slow plant development early in the season has contributed to an increased incidence of Type III bronzing in South East Queensland this season.

According to crop scouts, levels of bronzing observed in the field have declined over the last  week, and we hope that this decline will continue.

Pink Wax Scale

At this time of year we commonly get enquiries about pink wax scale. This pest occurs on a variety of plants including fruit trees such as citrus, mango, avocado, custard apple as well as some garden plants including lillypilly and umbrella tree.

In Queensland there are usually two generations per year. Typically one of these occurs in late spring and the second in early autumn. Like other scale insects, pink wax scale settles early in its life and never moves again. The young stages (crawlers) emerge from under the body of the adult female to settle nearby. They may also be carried easily on wind currents. Very quickly they start to produce their characteristic protective waxy covering.

Wax scales generally do best in humid coastal districts where temperatures are more moderate. They can produce large quantities of honeydew causing a black sooty mould which can downgrade fruit and, if severe will even limit photosynthesis.

Biological control of pink wax scale

A range of predators and parasites will attack pink wax scale. Of the predatory insects both lacewings and cryptolaemus ladybird beetles will feed on this pest. The best agent however is a small wasp parasite called Anicetus beneficus. Anicetus wasps deposit their eggs into the scale insect and the larval stage consumes it from within. Unfortunately however the wasp is not commercially available.

Oil sprays to control pink wax scale

An oil spray can help reduce numbers of pink wax scale but only if timed correctly and applied thoroughly. This should be applied when crawlers are emerging and first stage nymphs are settling on the leaves of the host plant. This is the only time the insects are sufficiently vulnerable for the spray to be effective.

 

Tips for establishing a ladybird population

Ant Control

In the farm or orchard

Again ants will only expend energy climbing onto trees, vines or other plants if there is some reward. To some extent this can be a ‘chicken and egg’ situation. Are the ants there because of the mealybugs or vice versa?

Ant baits

A variety of ant baits are available. The simplest of these is an old but well tested bait which incorporates borax as the toxicant. Small quantities of this relatively innocuous compound are taken back to the nest by an army of ant workers. It takes some time but eventually this action can reduce in size or kill out the colony. The important thing about an ant bait is that it should not be so toxic as to kill individual ants quickly before they have had a chance to return to the nest to transfer the toxicant to the colony at large.

A simple recipe for an ant bait is 3 cups of water + 1 cup of sugar with 4 teaspoons of borax. Some ant species prefer more or less sugar or may respond to protein (crushed dry dog food formula can work here).

Some commercial ant baits are available and these can be more or less effective. It is important to understand the habit of the ant species that is causing your problems before choosing your ant management strategy.

Ant barriers

Because ants do not have wings (other than when swarming) we can exclude them if plants or other valued items are kept on elevated benches. The use of sticky barriers can be an effective tool. In this case it is important that there are not alternative access points that the ants can use. There are several sticky compounds available for this purpose. It may be necessary to re-work the material or apply a fresh band from time to time as dust and leaves can reduce the effectiveness of the barrier allowing ants across.

A simple water barrier can also be a great way to stop ants in the home. A water bath can be used to prevent ants from accessing the honey jar or the kitchen bin.

 

Cryptolaemus ladybird being attacked by ants

 

Trichogramma: the cornerstone of successful IPM at Mulgowie Farming Company

Mulgowie Farming Comapany is the largest producer of fresh sweet corn and beans in Australia. Their production manager, Andrew Johansen, offered the following feedback about the role of our Trichogramma parasitoid wasps in their successful IPM program.

“Mulgowie Farming Company has been using Trichogramma wasps for around five years now, and it has become the cornerstone to our IPM strategy in sweetcorn. By releasing Trichogramma wasps and using only “soft” or biological spray applications we have been able to reduce our grub damage while at the same time reducing our spray applications and totally avoiding the use of heavy chemicals. This is a win-win situation by reducing spraying costs and producing an environmentally friendly product that is healthier for people and the environment.”

– Andrew Johanson, Production Manager

Biological control of Solenopsis mealybug: the potential of Cryptolaemus montrouzieri

A recent paper by Kaur and Virk published in Phytoparasitica explores the feeding potential of Cryptolaemus montrouzieri against Solenopsis mealybug (Phenacoccus solenopsis). Their results suggest that the native Australian ladybird beetle  C. montrouzieri, which is the species produced by Bugs for Bugs for the Australian market, has the potential to be exploited as a biocontrol agent in North India.

Click here to view the paper.

Monitoring Fruit Fly Populations

Why monitor fruit flies:

  • Counting and recording fruit fly populations helps us understand fruit fly activity in an area.
  • We can use this information to fine tune control programs.

Trap placement:

  • Put fly traps in your orchard at: 1 per ha (small orchards) 2 per ha (large orchards).
  • Place each trap in a healthy fruit tree at head height.

Recording fruit fly numbers:

  • Each week count, record and remove any flies that have collected in the trap.
  • Replace fruit fly wick every 3 months.

Additional information:

  • The traps only catch male fruit flies.
  • The number of flies caught does not necessarily indicate the size of the population but can indicate population trends.
  • Fruit fly traps do not control fruit fly. You must use protein bait sprays also to achieve this.

Another Cryptolaemus vs. mealybug good news story

 

Hi fellow bug lovers,

Thank you for providing me with these wonderful Cryptolaemus! They have totally destroyed my mealy bug infestation of which I battled for two years.

I have a 20 year old Hoop Pine tree in the front garden in which there are numerous bird’s nests and I thought that I had tried everything.These wonderful beetles battled the odds and ate anything mealybug.

There has been no sign of re-infestation,despite the hot weather we’ve been experiencing. I’m not worried if they do re-appear as I know that they can be controlled. Anyway, at this stage, all looks good.

Thank you all for your excellent service and fantastic product.

Kind Regards,

Mac Hosking,

Gladstone, 22 January 2009