Melon aphid resistance management

Aphis gossypii can become
resistant to many insecticides.
(Photo: Clemson University,
www.insectimages.org)

N.A. Martin¹ and P.J. Cameron²
¹Crop and Food Research, Private Bag 92169, Auckland, New Zealand
²20 Westminster Rd, Mt Eden, Auckland 1003, New Zealand

(Revised October 2004)

Reason for strategy and update

Melon aphid, Aphis gossypii, also known as cotton aphid, is capable of becoming resistant to a wide range of insecticide groups. Pest management strategies aimed at preventing or minimising resistance will help maintain control and conserve the effectiveness of existing products. This is an update of the resistance management strategy (Martin & Cameron 1997).

Background

Melon aphid is a polyphagous species that can transmit some plant damaging viruses. It has been recorded from more than 50 plant families (Steenis 1995). Melon aphid has a variety of life cycle strategies and it is not known if any populations require special overwintering hosts or if sexual forms occur in New Zealand.

Melon aphid (Aphis gossypii) has an indefinite number of anholocyclic lines (asexually reproducing populations), some of which may have particular host associations (Blackman & Eastop 1984). Each line can have distinct and different host plant preferences.

Melon aphid can transmit over 50 viruses (Blackman & Eastop 1984) including water melon mosaic virus (WMV) and zucchini yellow mosaic virus (ZVMV), which occur in New Zealand. Because feeding damage is less significant than virus infection, it is possible to tolerate larger melon aphid populations when virus sources are removed or reduced.

Products with label claims for melon aphid control in New Zealand

**Table 1:** Products with label claims for *Aphis glossypii* (melon aphid) control in New Zealand (October 2002). For a summary of the details of the claims for each crop see Table 2.
Pesticide category	IRAC chemical group	Pesticide common and (product) names
Parasites		Aphidius colmani (Aphidius, Aphipar)
Predators		Aphidoletes aphidimyza (Aphidoletes)
Carbamate	1A	methomyl (Lannate)
Carbamate	1A	pirimicarb (Pirimor)
Organo-phosphate	1B	acephate (Lancer, Orthene)
		acephate and triforine (Saprene)
		chlorpyrifos (Chlorpyriphos, Lorsban, Pychlorex, Spectrum)
		diazinon (Basudin, Dew, Diazinon, Diazinyl, Gesapon)
		dichlorvos (Nuvos)
		dimethoate (Rogor)
		maldison (Malathion, Yates Maldison)
		methamidophos (Metafort)
		terbufos (No longer registered)
		thimet (No longer registered)
Organophosphates/pyrethroids	1B/3	pirimiphos-methyl + permethrin (Attack) mixture
Cyclodiene	2A	endosulfan (No longer registered)
Pyrethroid	3	alpha-cypermethrin (Bestseller, Dominex, Fastac)
		bifenthrin (Talstar)
		deltamethrin (Decis Forte, Deltaphar)
		taufluvalinate (Mavrik, Supershield, Guardall)
Pyrethrins	3	pyrethrum (Garlic & Pyrethrum, Yates Pyrethrum)
Chloronicotinyl	4A	imidacloprid (Confidor 5GR, Gaucho)

Current status of melon aphid resistance in New Zealand

In New Zealand, a population of melon aphids has been found with resistance to methomyl, demeton-S-methyl and acephate (Martin & Workman 1997).

Overseas, melon aphid is resistant to a wide variety of insecticides, including organochlorines, many organo-phosphates, carbamates and synthetic pyrethroids (e.g. Georghiou 1981; Hollingsworth et al. 1994; Silver et al. 1995).

Resistance management and prevention strategy

The general strategy aims to reduce the need for control of melon aphid by reducing virus sources and aphid reservoirs. Selection pressure on aphids in crops can then be reduced by applying insecticides only when necessary to reduce feeding damage.

Note: Control failure does not always imply resistance.

The following guidelines are recommended:

Maximise virus control by standard management practices. These include:
- use of virus-free seed (e.g. from pathogen testing schemes) or virus-free transplants
- removal of infected plants within a crop
- elimination of weed sources that may harbour viruses
- removal of volunteer crop plants
- use of virus-resistant cultivars
- use of screens to prevent aphids entering greenhouses
Remove alternative host plants for melon aphid, e.g. solanums, brassicas and ornamentals to create virus-free zones.
Maximise biological control (especially in greenhouses) using parasitoids, predators or fungal pathogens of aphids.
Monitor plants to ensure insecticides are applied only when necessary.
Choice of effective insecticides should be based on a knowledge of insecticide resistance in local populations. Resistance to pirimicarb, lambda-cyhalothrin and tau-fluvalinate now appears to be widespread.
Use the correct label rates and application procedures.
Alternate between insecticide groups.
If control failures are suspected, crops should be treated with an insecticide from a different chemical group.

Research strategy

The distribution of resistance among the major cropping areas should be assessed regularly.

**Table 2:** Products with label claims for control of *Aphis glossypii*, melon aphid (MA), in New Zealand (October 2002). Not all products listed for each pesticide may have a label claim for all crops indicated. Pesticide category and IRAC chemical group are given in bold. Product names are in Table 1.
	Type of label claim for each crop¹
Pesticide category and IRAC chemical group Pesticide common and (product) names
Parasites
Aphidius colmani							A in GH				A in GH
Predators
Aphidoletes aphidimyza							A in GH				A in GH
Carbamates 1A
methomyl	GPA		GPA		GPA	GPA in VB			A		GPA
pirimicarb	A	A	A	A	A	A
Organo-phosphate 1B
acephate			A	A		GPA				A	A
acephate and triforine											A
chlorpyrifos		A in SQ				A					A
diazinon	A		A		A	A in VB	A	A in CIT	A	A	A
dichlorvos						A	A		A in BF		A
dimethoate		A in MW		A		CA in VB, A in FB			A
maldison						A	A				A
methamidophos	A			A
terbufos (No longer registered)						A in FB
thimet (No longer registered)		A		A		A			A		A
organo-phosphates + pyrethroids 1B/3
pirimiphos-methyl + permethrin mixture		A in GH			A in GH	A in VB
Cyclodiene 2A
endosulfan				A	A	A in VB			A		A
Pyrethroids 3
alpha-cypermethrin					A
bifenthrin		A			A						A
deltamethrin		A in SQ
taufluvalinate					GPA					GPA	A
Pyrethrins 3
pyrethrum							A	A			A
Chloronicotinyl 4A
imidacloprid (Confidor 5GR)							A in TSP				A in TSP
imidacloprid (Gaucho)		A in SQ		A		A in FB

¹A = aphids, GPA = green peach aphid (Myzus persicae), CA = cabbage aphid, VB = vegetable brassicas, FB = forage brassicas, BF = berry fruit, GH = greenhouses, TSP = transplants, CIT = citrus, SQ = squash, MW = marrow. Beans excludes broad beans.

Implementation

Growers should implement virus control strategies.
Growers should monitor plants to ensure insecticides are only applied when necessary.
Insecticides registered for use against melon aphid should carry the following label statement:
IMPORTANT - RESISTANCE MANAGEMENT
Resistance to this pesticide may develop from excessive use. To minimise this risk use strictly in accordance with label instructions. Avoid using this insecticide exclusively all season and avoid unnecessary spraying or other methods of application. Maintain good cultural practices.

References

Blackman RL, Eastop VE 1984. Aphids on world crops: an identification and information guide. John Wiley & Sons, Chichester, UK.

Georghiou GP 1981. The occurrence of resistance to pesticides in arthropods, an index of cases reported through 1980. FAO of UN, Rome. 172 pp.

Hollingsworth RG, Tabashnik BE, Ullman DE, Johnson MW, Messing R 1994. Resistance of Aphis gossypii (Homoptera: Aphididae) to insecticides in Hawaii: spatial patterns and relationship to insecticide use. J. Economic Entomoogy 87: 293-300.

Martin NA, Cameron PJ 1997. Melon aphid resistance management strategy. Proceedings 50th N Z Plant Protection Conference: 551-555.

Martin NA, Workman PJ 1997. Melon aphid (Aphis gossypii): resistance to pesticides. Proceedings 50th N Z Plant Protection Conference: 405-408.

Silver ARJ, van Emden HF, Battersby M 1995. A biochemical mechanism of resistance to pirimicarb in two glasshouse clones of Aphis gossypii. Pesticide Science 43: 21-29.

van Steenis M 1995. Evaluation and application of parasitoids for biological control of Aphis gossypii in glasshouse cucumber crops. Ph. D. Thesis, Wageningen, Netherlands.