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 T.J.B. Herman, January 2025)

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 mode of action (MoA) 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 previous resistance management strategies (Martin & Cameron 1997 and 2004).

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 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 watermelon 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 melon aphid control in New Zealand (November 2024)
Beneficial insects
Species	For use against	Crops for use in
Aphidius colmani (parasitoid)	Aphids	Mainly greenhouse crop
Tasmanian lacewing (Micromus tasmaniae)	Aphids (generalist predator)	Mainly greenhouse crops
Orius pirate bug (Orius vicinus)	Thrips (generalist predator)	Mainly greenhouse crops
Dusky ladybird (Scymnus loewii)	Aphids (generalist predator)	Mainly greenhouse crops

Active ingredient(s)	Registered for	Crops registered for use
IRAC insecticide mode of action group
1A Carbamates
Methomyl	Aphids, GPA	Beans, cabbage, cauliflower, lettuce, strawberries, tomatoes
Pirimicarb	Aphids	Various fruit and vegetable crops
1B Organophosphates
Acephate	Aphids, GPA	Avocadoes, cabbage, cauliflower, citrus, lettuce, ornamentals, tamarillos
Acephate	It is an offence to use this product off label
Chlorpyrifos	Aphids	Grapes, brassicas, lucerne, winter squash
Diazinon	Aphids	Cereals, oranges, mandarins, strawberries, tomatoes (outdoor)
Dichlorvos	Aphids	Berryfruit, cereals, lucerne, orchards, vegetables, fodder crops
Maldison	Aphids	Orchards, field crops, vegetables
1B + 3A Organophosphates + pyrethroids
Pirimiphos-methyl + permethrin	Aphids	Brassicas, citrus, greenhouse tomatoes and cucumbers, fodder beet
3A Pyrethroids & pyrethrins
Alpha-cypermethrin	Aphids, green peach aphids	Stone fruit, tomatoes
Bifenthrin	Aphids	Field tomatoes, buttercup squash and pumpkins, ornamentals
Deltamethrin	Aphids	Lucerne, winter squash
Taufluvalinate	Aphids – black cherry, leaf-curl plum, green peach, cereal, rose grain, blue green lucerne, grey cabbage	Cherries, peaches, plums, ornamentals, potatoes, tamarillos, field tomatoes, cereals, clover seed, beets, oil seed rape
Pyrethrins	Aphids	Ornamentals
4A Neonicotinoids
Imidacloprid	Aphids	Transplant drench – vegetable brassicas and lettuce, Seed treatments – cereals, forage brassicas, potatoes

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 (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:

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.
Promote biological control (especially in greenhouses).
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.
Use the correct label rates and application procedures.
Alternate between insecticide MoA groups.

If control failures are suspected, crops should be treated with an insecticide from a different chemical group.

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, Cameron PJ 2004. Melon aphid resistance management strategy. https://resistance.nzpps.org/index.php?p=insecticides/melonaphid

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.